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Ground Effect Aerodynamics of Race Cars
Abstract
We review the progress made during the last 30 years on ground effect aerodynamics associated with race cars, in particular open wheel race cars. Ground effect aerodynamics of race cars is concerned with generating downforce, principally via low pressure on the surfaces nearest to the ground. The "ground effect" parts of an open wheeled car's aerodynamics are the most aerodynamically efficient and contribute less drag than that associated with, for example, an upper rear wing. While drag reduction is an important part of the research, downforce generation plays a greater role in lap time reduction. Aerodynamics plays a vital role in determining speed and acceleration (including longitudinal acceleration but principally cornering acceleration), and thus performance. Attention is paid to wings and diffusers in ground effect and wheel aerodynamics. For the wings and diffusers in ground effect, major physical features are identified and force regimes classified, including the phenomena of downforce enhancement, maximum downforce, and downforce reduction. In particular the role played by force enhancement edge vortices is demonstrated. Apart from model tests, advances and problems in numerical modeling of ground effect aerodynamics are also reviewed and discussed.
... The significant advancements achieved to enhance vehicle ride performance over 17 the past few decades have significantly contributed to the automotive industry. The 18 two essential components of a vehicle's ride performance that have received the interest 19 of numerous researchers are ride comfort and road-holding capability [1,2]. Ride 20 comfort is related to the unpleasant vibrations of the vehicle body transmitted to the 21 passengers. ...
... Active aero- 41 dynamic control (AAC) strategies are also effective in improving the lateral performance 42 of a road vehicle. The AACs are employed to manipulate the aerodynamic surfaces 43 to generate varying negative lift forces to enhance the vehicle's handling capability 44 [17][18][19]. In our previous work [20], we have analyzed that the aerodynamic surfaces 45 can generate negative lift force to improve the ride quality of a vehicle considering 46 pitch and roll dynamics. ...
... The performance index presented in equation (19) can be written in matrix form regarding the difference between the desired and current state, the jerk control inputs, and jerk disturbance inputs. ...
This paper presents designing an attitude motion control strategy for a half-car model using an anti-jerk predictive controller. Anti-jerk predictive controller based on active aerodynamics surfaces is employed to deal with the anticipated future road maneuvers and improve vehicle ride performance by canceling out external jerks acting on the vehicle body. The body jerks are produced during vehicle traversing on a double lane-change maneuver, acceleration, or braking. The control strategy helps the vehicle to achieve a realistic operation of the active aerodynamic surface to improve the vehicle’s ride performance, i.e., ride comfort and road holding during cornering, acceleration, or braking. The anti-jerk predictive controller is developed based on the predictive control strategy, which predicts future road inputs and uses them to compensate for the vehicle’s attitude motion. The simulation results show that the proposed control strategy effectively reduces the effects of vehicle body jerks transmitted to the passengers, improving ride comfort without degrading vehicle handling. The anti-jerk predictive controller successfully tracks the desired attitude position by canceling the external body jerks.
... Aerodynamics has become a crucial aspect of high-speed car performance. The race-car industry has led technology innovation by indicating the need for constant improvement [3]. Engineers have been striving to sculpt the shape of the cars to manipulate and take advantage of the flow round the body. ...
... This is usually achieved on a highspeed ground vehicle by introducing aerodynamic devices such as wings and undertrays, which modify the airflow to suit the engineering needs [4]. In the race-car industry, the primary aim is to maximise the downforce while maintaining the lowest possible drag [3], but achieving consistent performance at diverse speeds and maximising acceleration is also essential. The magnitude of the downforce significantly affects braking, acceleration, and cornering -and hence the cornering speed. ...
... However, the ground-effect aerodynamics that applies to an open-wheeled car is still an experimental science [3]. This is due to the complex flow physics that involves the interaction of a turbulent wake, the ground boundary layer, dynamic suspension motion, and many more factors, in which accurate analytical capability (both experimental & computational) has not yet been sufficiently developed. ...
Research into undertray devices in the high-speed racing industry is still privileged information — this is indicated by the lack of research papers which are forthcoming in the field. In this project, the downforce and drag of an undertray were investigated in two and three dimensions by employing Computational Fluid Dynamics (CFD). Three sets of analyses were undertaken, consisting of 2D enclosed flow, 2D open flow, and 3D open flow, and these were followed by calculations on prototype undertrays to gain a fundamental understanding of the effect of an undertray’s flow features on its performance in diverse geometrical setups. Two dimensional simulation was determined not to be optimal for undertray analysis, as it does not properly capture important flow features, which turn out to require three dimensional calculations. The three dimensional analysis has also shown the importance of strategic management of effective flow control using generation of vortices to maintain flow attachment on the undertray’s wall and to generate stable vortices to exploit the flow, improving the downforce and reducing drag. The final undertray design geometry was based on these analyses. The final result was found to give a 184.1 N increase in downforce and 10.5 N reduction in drag at 40 km/h. Further research into key flow features and vortex generation and their effect on the undertray overall performance is required to utilise the potential performance of an undertray fully.
... The analysis is framed by three key studies: Zhang et al.'s exploration of ground effect aerodynamics, Diasinos et al.'s investigation of ride height effects on front wing-wheel interactions, and Mokhtar's research on high-lift wings with ground effect. Zhang et al. (2006) emphasizes the critical role of ground effect aerodynamics in generating downforce through low pressure on surfaces nearest to the ground. This foundational understanding underscores the importance of optimizing the design and configuration of venturi tunnels to maximize downforce while minimizing drag. ...
... This aligns with the current study's focus on optimizing the venturi tunnels' configuration to enhance downforce. [3] Diasinos et al. (2017) investigate the impact of varying ride heights on the aerodynamic interactions between the front wing and wheel of a racing car. Their findings indicate that different height-to-chord ratios significantly influence the vortex flow patterns and the resulting aerodynamic forces. ...
... The control of vortex shedding through the proximity effects of a moving wall, for instance, can be classified as an active method [11] of controlling both the hydrodynamic boundary layer and viscous wake development behind a bluff body. The mentioned example was originary of experimental investigations resulting in the use of a belt moving [12][13][14]. ...
... The use of a moving wall serves to eliminate the less influential effects of the boundary layer formed on the wall [12,37]. Zhang et al. [14] stated that the physically correct experimental method for modeling the ground effect is to employ a belt moving at free-flow velocity. However, the author considers that "It is difficult to maintain the correct moving ground condition. ...
This paper contributes to a new Lagrangian vortex method for the statistical control of turbulence in two-dimensional flow configurations around a rough circular cylinder in ground effect when considering higher subcritical Reynolds numbers, namely 3 × 10⁴ ≤ Re ≤ 2 × 10⁵. A smoothed moving wall (active control technique) is used to include the blockage effect in association with the variation in cylinder surface roughness (passive control technique), characterizing a hybrid approach. In contrast with the previous approaches of our research group, the rough cylinder surface is here geometrically constructed, and a new momentum source term is introduced and calculated for the investigated problem. The methodology is structured by coupling the random Discrete Vortex Method, the Lagrangian Dynamic Roughness Model, and the Large Eddy Simulation with turbulence closure using the truncated Second-Order Velocity Structure Function model. This methodological option has the advantage of dispensing with the use of both a refined near-wall mesh and wall functions. The disadvantage of costly processing is readily solved with Open Multi-Processing. The results reveal that intermediate and high roughness values are most efficient for Reynolds numbers on the orders of 10⁵ and 10⁴, respectively. In employing a moving wall, the transition from the large-gap to the intermediate-gap regime is satisfactorily characterized. For the conditions studied with the hybrid technique, it was concluded that the effect of roughness is preponderant and acts to anticipate the characteristics of a lower gap-to-diameter ratio regime, especially with regard to intermittency.
... The car floor area or undertray can create half of the total downforce in a Formula 1 car. Apart from that, this device is also efficient in its use in several racing cars [5] [6] [7]. This is because the front of the car's floor area is small so that it can produce many downforces without increasing drag. ...
... The venturi tunnel design gives the undertray of the car converging and divergent curves to accelerate the flow of wind under the car, thereby creating a ground effect [5]. This proved to be successfully used by the Lotus F1 team by dominating the 1978 Formula 1 Grand Prix racing event using the Lotus 79 car. ...
Undertray is the term for the venturi tunnel under the car body, which can increase the traction and acceleration of a racing car due to increased downforce. This research aims to find the optimal undertray geometry for formula student racing vehicles. The modification carried out in the research compared three undertray geometry variation designs to produce a design with the highest downforce value and the lowest drag coefficient. Testing was conducted using Computational Fluid Dynamics (CFD) by giving each design a wind speed of 80 km/hour, 90 km/hour, and 100 km/hour. After testing, the values for downforce, 12 A. Nowak, T. Kowalski (Authors)-12-POINTS drag coefficient, turbulence kinetic energy contour, pressure, speed, and streamline behavior were obtained. As a result, the drag coefficient value is not too influenced by changes in speed but is more influenced by the shape of the undertray geometry. In contrast, the downforce value increases in direct proportion to the increase in car speed. The optimization also compared the effect of adding a diffuser with the same geometry to each undertray design. The research results show that adding a diffuser reduces the drag coefficient by 0.28% and downforce by 1.103%. Meanwhile, adding an undertray increases downforce by 102.3% for student formula cars compared to not using an undertray tunnel. The simulation results show that the most optimal design to use is the undertray 3 design with a diffuser because it has proportional drag and downforce coefficient values compared to without an undertray. Even though the results of this research show that the most considerable downforce value is produced by undertray design 1 with a diffuser, the coefficient of drag value for design 1 has the highest value, so the design is not proportional to use.
... This effect is attributed to the suction induced by the vortex generated at the edge of the endplate, known as the edge vortex. Due to the pressure difference between the sides of the endplate, there is infiltration of airflow from the outer endplate region to the lower low pressure inner region of the wing [3]. ...
... The aerodynamics forces were obtained with an average error of order 1.5% for lift and 5.6 % for drag. As an application work, like previous investigations [2][3][4][5], this study does not delve into extensive details about the measurement techniques. ...
... Other experimental approaches, such as the one led by Zhang et al. [15], have evaluated the usage of sealing skirts on the underbody to channelise and direct the flow towards the exit diffuser section. The latter, along with a proper diffuser angle, can provide a significant 32.5% increase in the downforce coefficient when compared to a baseline model. ...
... Surface flow visualisation at diffuser angles of (a) 5 • , (b) 10 • and (c) 15 • (Reprinted with permission from the University of Southampton[15]). ...
The aerodynamic complexity of the underbody surfaces of conventional road vehicles is a matter of fact. Currently available literature is focused mainly on very simple Ahmed-body geometries as opposed to realistic car shapes, due to their complexity and computational cost. We attempted to understand the flow behaviour around different realistic conventional road car geometries, and we provide an extensive evaluation of the aerodynamic loads generated. The key findings of this article could potentially set a precedent and be useful within the automotive industry’s investigations on drag-reduction mechanisms or sources of downforce generation. The novelty of the work resides in the realistic approach employed for the geometries and in the investigation of barely researched aerodynamic elements, such as front diffusers, which might pave the way for further research studies. A baseline flat-underfloor design, a 7∘ venturi diffuser-equipped setup, a venturi diffuser with diagonal skirts, and the same venturi diffuser with frontal slot-diffusers are the main configurations we studied. The numerical predictions evaluated using RANS computational fluid dynamics (CFD) simulations deal with the aerodynamic coefficients. The configuration that produced the highest downforce coefficient was the one composed of the 7∘ venturi diffuser equipped with diagonal sealing skirts, achieving a CL value of −0.887, which represents an increase of around 1780% with regard to the baseline model. That achievement and the gains in higher vertical loads also entail a compromise with an increase in the overall air resistance. The performance achieved with diffusers in the generation of downforce is, as opposed to the one obtained with conventional wings, a cleaner alternative, by avoiding wake disturbances and downwash phenomena.
... These, again accompanied by sliding skirts in order to seal the flow under the floor, generated large amounts of downforce compared to flat underfloors, which allowed the car to win the world championship [97]. After sliding skirts were banned for safety reasons and flat-bottomed underfloors became mandatory [98], renewed interest in employing ground effect into car design appeared and the concept of a diffuser-an upswept section of the underfloor at the rear of the car-was introduced for the first time. ...
... Zhang et al. [98] presented downforce distributions of a generic open-wheeled race car on the front and rear axles with respect to front and rear ride height, which jointly define ride height and rake angle. Front downforce coefficient was shown to increase monotonically with decreasing front and increasing rear ride height, or increasing rake angle. ...
This research project was focused on two related topics—hardware-in-the-loop aero- dynamic optimisation, and aerodynamics of automotive underbody diffusers in the presence of rake, defined as an inclination of the underfloor with respect to the ground. Two experimental systems were used for automatic, closed-loop optimisation trials, and for mapping of aerodynamic performance. Each consisted of an Ahmed-type body with a diffuser, with three controlled degrees of freedom, i.e. the model’s height above the ground, and inclinations of the underfloor and diffuser plates. The systems were equipped with force acquisition for optimisation and performance quantification purposes, and with surface pressure measurements to inspect the underlying flow patterns.
The high-speed system was used for real-time optimisation runs using a range of algorithms in order to determine their suitability to problems of this type. Population-based algorithms, and genetic algorithms in particular, were found to provide the most reliable convergence in spite of the noise and hysteresis in the measurements. Reductions in pre-sampling delay and sampling time decreased the average function evaluation time without negatively impacting convergence performance, whereas combinatorial optimisation was used to minimise actuation overheads. Subsequently, both methods were shown to improve overall optimisation efficiency during experimental trials.
Finally, the impact of rake on diffuser aerodynamics was investigated through quasi- static variations of the three degrees of freedom. Introducing rake was found to induce significant pressure recovery beneath the underfloor, causing strong suction under the front of the body and increased downforce. Furthermore, two counter-rotating vortices were observed along the edges of the underfloor, whose formation and strength depended on the configuration of the model, and which significantly affected the stall characteristics of the diffuser.
... The most precise technique for modelling GE is the moving belt system, which simulates the relative motion of the ground by running a belt at freestream velocity, though it comes with practical difficulties, including vibrations and belt flatness [8]. Werle's work in the 1960's further highlighted the significant differences between these methods, particularly in flow separation and vortex behaviour under various conditions [9]. GE phenomena are generally classified into two categories: two-dimensional (2D) chord-dominated GE and threedimensional (3D) span-dominated GE [10]. ...
The flow dynamics and performance of tandem foils, both with and without ground effect (GE), continue to present challenges that are critical to understanding and optimizing aero/hydrodynamic systems, particularly for applications in next-generation wing-in-ground (WIG) effect vehicles, sailing yachts, and hydrofoil vessels. The performance of foils in GE (IGE) versus out of GE has not been extensively compared. This comprehensive study investigates the aero/hydrodynamic performance and flow dynamics of tandem foils using NACA 4412 section at moderate Reynolds number. To isolate the effects of spacing and ground clearance (H), both foils were set at a fixed angels of attack to negate the influence of decalage angle. The design variables examined include horizontal and vertical spacing between the foils, as well as H. Performance comparisons in both GE and out-of-GE conditions were presented, focusing on lift-to-drag ratio, lift and drag, and foil-to-foil interaction dynamics. Numerical simulations were conducted using the finite-volume method to solve the incompressible Reynolds-averaged-Navier-Stokes equations with the shear-stress transport k-ω turbulence model with gamma-transition model. Results indicate that the superiority of tandem foils is highly configuration-dependent. IGE, tandem foils exhibit a significantly higher lift-to-drag ratio than in out-of-GE conditions, where their performance is often lower than that of isolated foils. Positive G between the foils were found to enhance aero/hydrodynamic efficiency, suggesting that optimizing the gap distance can lead to performance improvements. The stagger distance plays a critical role in altering the static pressure distribution due to foil-to-foil interactions. Notably, under certain interference conditions, the fore foil can experience reduced drag or even generate thrust, offering potential advantages for specific aero/hydrodynamic applications. These findings provide new insights into the behaviour of tandem foils and may inform the design of next-generation WIG vehicles, hydrofoil vessels, tandem sails, and other systems where foil interactions are significant.
... Ground effect aerodynamics, which exploit the accelerated flow between the car underbody and the track surface, represent another critical aspect of Formula One performance. Zhang et al. (2006) reviewed the principles and applications of ground effect in racing cars, noting the significant downforce enhancement possible through properly designed underbody geometries and diffusers. The interaction between underbody flow and surface features presents a potential application area for biomimetic structures. ...
This research investigates the application of biomimetic fish scale-inspired surface structures for aerodynamic drag reduction in Formula One racing. Through a multidisciplinary approach combining biological principles, computational fluid dynamics (CFD), and experimental validation, we demonstrate that properly designed biomimetic surface patterns can significantly reduce aerodynamic drag while maintaining other performance characteristics. Our optimised biomimetic surface design, based on overlapping fish scale arrays with specific geometric parameters, achieved drag reduction of up to 10.2% in CFD simulations and 9.5% in experimental testing. The primary mechanism involves the generation of organised streamwise velocity streaks within the boundary layer, which stabilise laminar flow and delay transition to turbulence. Implementation considerations for Formula One applications are discussed, including manufacturing approaches, regulatory compliance, and estimated performance benefits. The findings suggest that biomimetic fish scale arrays represent a promising passive flow control strategy for Formula One aerodynamics, with potential applications extending to other transportation and fluid handling systems.
... Hence, car manufacturers need to evaluate the aerodynamic performance under yawed flows in the development loop of a new vehicle (D'Hooge et al. 2014). The development could be massively accelerated by using a surrogate model instead of re-running the simulations and wind-tunnel tests that are needed to characterize the aerodynamic performance of a road vehicle (Zhang et al. 2006) at every angle of interest. ...
A deep-learning-based closure model to address energy loss in low-dimensional surrogate models based on proper-orthogonal-decomposition (POD) modes is introduced. Using a transformer-encoder block with easy-attention mechanism, the model predicts the spatial probability density function of fluctuations not captured by the truncated POD modes. The methodology is demonstrated on the wake of the Windsor body at yaw angles of [2.5,5,7.5,10,12.5], with 7.5 as a test case. Key coherent modes are identified by clustering them based on dominant frequency dynamics using Hotelling T2 on the spectral properties of temporal coefficients. These coherent modes account for nearly 60% of the total energy while comprising less than 10% of all modes. A common POD basis is created by concatenating coherent modes from training angles and orthonormalizing the set, reducing the basis vectors from 142 to 90 without losing information. Transformers with different size on the attention layer, (64, 128 and 256), are trained to model the missing fluctuations. Larger attention sizes always improve predictions for the training set, but the transformer with an attention layer of size 256 overshoots the fluctuations predictions in the test set because they have lower intensity than in the training cases. Adding the predicted fluctuations closes the energy gap between the reconstruction and the original flow field, improving predictions for energy, root-mean-square velocity fluctuations, and instantaneous flow fields. The deepest architecture reduces mean energy error from 37% to 12% and decreases the Kullback--Leibler divergence of velocity distributions from KL=0.2 to below KL=0.026.
... It is observed that the yaw angle ranges from 0° to 15° irrespective of the vehicle shape [2]. To evaluate the new vehicle computational fluid dynamics [3], machine learning [4] and wind tunnel testing is essential [5]. Advanced manufacturing [6] plays a crucial role in the testing of vehicle aerodynamics due to its ability to facilitate the rapid production of complex components and prototypes with high precision and accuracy. ...
... As such, the complex flow features associated with individual components are often interwoven and difficult to separate. Nevertheless, a clear understanding of flow physics connected to individual aerodynamic components is a prerequisite for gaining an insight into the overall flow field and eventually a better vehicle design [10]. This section will talk about the effects of the front spoiler, rear spoiler (tail) and vortex generators on the force analysis of the car. ...
Nowadays, cars are used quite often and require good stability and handling while driving to keep passengers safe. At the same time, the race car also must have better stability and handling at high speeds than family cars so that they can ensure that the driver can handle the track and get the best performance in extreme conditions. Therefore, the shape of the vehicle and the design of the different components play a key role in ensuring its stability at high speeds. From an aerodynamic point of view, the streamlined body design, the application of spoilers, the design of the tail and the ground effect are all factors that are crucial to the stability of the car. This paper will look at how the race car remains stable at high speeds from an aerodynamic perspective, and how its shape and different components of the car affect its stability and handling. From our research, we find that all of them have crucial effects and exist different forces on the car body
... The aerodynamic evaluation of a new vehicle entails a combination of computational fluid dynamics simulations and wind tunnel testing [3]. Both methodologies are highly expensive, and their costs limit the amount of geometries and flow conditions that can be tested. ...
This study introduces a deep learning surrogate model designed to predict the evolution of the mean pressure coefficient on the back face of a Windsor body across a range of yaw angles from 2.5∘ to 10∘. Utilizing a variational autoencoder (VAE), the model effectively compresses snapshots of back pressure taken at yaw angles of 2.5∘, 5∘, and 10∘ into two latent vectors. These snapshots are derived from wall-modeled large eddy simulations (WMLESs) conducted at a Reynolds number of ReL=2.9×106. The frequencies that dominate the latent vectors correspond closely with those observed in both the drag’s temporal evolution and the dynamic mode decomposition. The projection of the mean pressure coefficient to the latent space yields an increasing linear evolution of the two latent variables with the yaw angle. The mean pressure coefficient distribution at a yaw angle of 7.5∘ is predicted with a mean error of e¯=3.13% when compared to the WMLESs results after obtaining the values of the latent space with linear interpolation.
... 19 In the steady ground effect, airfoils experience higher lift near the ground due to the deceleration of airflow beneath the lower surface, resulting in increased lower surface pressure and non-formation of wing-tip vortices, reducing induced drag. 38 In most cases, higher underside pressures are typically the result of the stagnation point moving further downstream on the lower side of the airfoil. Steady ground effect has been widely observed in nature. ...
Several advanced medical and engineering tasks, such as microsurgery, drug delivery through arteries, pipe inspection, and sewage cleaning, can be more efficiently handled using micro- and nano-robots. Pressure-driven flows are commonly encountered in these practical scenarios. In our current research, we delve into the hydrodynamics of pitching hydrofoils within narrow channels, which may find their potential applications in designing bio-inspired robots capable of navigating through pressure-driven flows in confined channels. In this paper, we have conducted a numerical investigation into the flow characteristics of a National Advisory Committee for Aeronautics (NACA) 0012 hydrofoil pitching around its leading edge within a plane Poiseuille flow using a graphical processing unit accelerated sharp interface immersed boundary method solver. Our study considers variations of the wall clearance from 20% to 50% of the channel width. We have explored the hydrodynamic features such as instantaneous and time-averaged values of lift, drag, input power, and torque for different wall clearance ratios and oscillation frequencies in the range of Reynolds number 100–200 based on the mean velocity and channel width. We have tried to explain the force, torque, and power variations by examining the flow features in the near wake. While the hydrodynamic coefficients showed significant variations with changes in wall clearance and the Strouhal number (St), we did not observe significant variations with alterations in the Reynolds number (Re).
... Because the evolved wake is bounded by or even interacted with the ground plane. The wake dynamics can vary dramatically to give the most important feature of such flow (Zhang et al., 2006). A thorough understanding of the wake dynamics of bluff bodies with ground effect is important, as it is related to numerous engineering applications, such as road vehicles, bridges, and wind farms. ...
For bluff-body flow, wake dynamics is important and associated with the flow-induced drag, lift, vibration and sound. The wake of bluff bodies placed in ground proximity is more complicated. Because the evolved wake is bounded by or interacted with the ground plane. It is important to understand the wake dynamics of bluff bodies with ground effect, as it is related to numerous engineering applications, such as road vehicles, bridges, and wind farms. In this paper, the wake dynamics of a D-shaped body in ground proximity is investigated experimentally, emphasizing the shear-layer interactions and the ground effect. The experiments are performed in a model wind tunnel at a subcritical Reynolds number of 2.3×10^4 and different gap-to-height ratios. Particle image velocimetry, hotwire velocimetry, and surface oil flow visualization are employed for the measurements. Wavelet analysis is used to examine the wake unsteadiness and Proper Orthogonal Decomposition is conducted to extract the coherent structures of the wake.
... In view of the relevance of the described problems, there is a large body of engineering-oriented work dedicated to ground effect (see the review [2] and its bibliography) and porpoising [3][4][5][6]. Our aim here is different. ...
... The recent research on sports cars by [14][15][16][17][18] used various control approaches to investigate the applications of AAS to improve ride comfort. To improve the vehicle's handling, AACs have been used to adjust aerodynamic surfaces and provide a range of negative lift forces [19][20][21]. In our earlier research [22,23], we examined how aerodynamic surfaces could produce a negative lift force to enhance a vehicle's ride quality while considering pitch and roll dynamics. ...
This study presents the effectiveness of an anti-jerk predictive controller (AJPC) based on active aerodynamic surfaces to handle upcoming road maneuvers and enhance vehicle ride quality by mitigating external jerks operating on the body of the vehicle. In order to eliminate body jerk and improve ride comfort and road holding during turning, accelerating, or braking, the proposed control approach assists the vehicle in tracking the desired attitude position and achieving a realistic operation of the active aerodynamic surface. Vehicle speed and upcoming road data are used to calculate the desired attitude (roll or pitch) angles. The simulation results are performed for AJPC and predictive control strategies without jerk using MATLAB. The simulation results and comparison based on root-mean-square (rms) values show that compared to the predictive control strategy without jerk, the proposed control strategy significantly reduces the effects of vehicle body jerks transmitted to the passengers, improving ride comfort without degrading vehicle handling at the cost of slow desired angle tracking.
... The ground-effect technology was first introduced by Lotus in the late 1970s to increase downforce and car speed around corners [22,23]. However, the inherent instability of the cars resulted in numerous accidents and fatalities. ...
This letter is the first report from a series of IEEE TIV's Decentralized and Hybrid Workshops (DHWs) on Intelligent Vehicles for Education (IV4E). The role of intelligent vehicles in promoting education for all ages through autonomous racing was discussed during a recent DHW. Over the past decade, autonomous racing has emerged due to advancements in self-driving technologies. While still focused on extreme speed, autonomous racing differs from conventional automobile racing in its development philosophy, as human drivers are no longer involved. The absence of human drivers should be regarded as a new chance to increase competitiveness and entertainment value. This letter discusses opportunities to promote education-oriented autonomous racing. Recall that the flagship car race is Formula 1, where “formula” denotes technical restrictions that should be satisfied strictly. We name the new race series Autonomous 1 or A1, leveraging the power of autonomous intelligence in education. The achievements made in Formula 1 and typical autonomous races are reviewed, followed by discussions about A1's future perspectives. Specifically, A1 needs to maintain race consistency, update rules, and provide personalized commentary to support all-age education.
... The low level of drag loads and increased lift loads adds to the fuel efficiency. In race car aerodynamics [12], [29], the lift forces in -ve z-direction pushes the Car downward with the negative angle of attack. ...
There is a strong interaction between air and vehicle components. Aerodynamics plays a significant role in a vehicle's fuel efficiency. The contact patch load between the tire and road is directly related to the vehicle load. In this research, the lift forces generated due to the additional wing attached to the car model with different spans and heights of the wing location from the car body is considered for study. The loads due to change in Angle of Attack (AOA) and their effect on the tire loads are studied. The upward vertical force produced from aerodynamic loads reduces the wheel load of the car virtually. A tire's coefficient of friction would decrease with upward vertical force. This balance load implies that a lightweight car would make more efficient use of its tires than a heavier car. ANSYS Fluent is used for the Computational Fluid Dynamics (CFD) study. The validation of airflow characteristics, lift and drag forces from simulations are done with wind tunnel testing data. Varying the angle of attack, wingspan, height between the car and the wing's lower surface, one can increase the capacity of the payload by 10% or fuel efficiency by 10% to 20%.
... The main purpose of applying aerodynamics during the design process of the F1 car is to obtain a F1 car with sufficient downforce and low drag force (Zhang et al., 2006) . Drag force acts as a resistance force for an object accelerating in the air flow region (Hetawal et al., 2014). ...
F1 IN SCHOOLS™ is a worldwide competition that is part of the efforts undertaken by the STEM educational model. In order to increase the performance of the F1 IN SCHOOLS™ car in terms of speed, two important parameters related to aerodynamic analysis are considered - drag coefficient and downforce coefficient. Drag force is a force that acts in the direction that is opposite of the car's motion, thus reducing the car's maximum speed. Meanwhile, sufficient downforce is beneficial to the car model because it allows the car's wheels to remain in contact with the track surface without going off-track. The most important component of a F1 IN SCHOOLS™ car is its front wing since its design has a significant effect on the drag coefficient and downforce coefficient induced by the air flow. Therefore, the objective of this study is to design a front wing that is capable of producing low drag coefficient while maintaining sufficient downforce coefficient. Moreover, this study also aims to examine the method of preventing flow separation at the rear part of the car model. This study will use Autodesk Inventor Professional to create the car mode. The simulation will be run using the STAR CCM+ software. The simulation will also be used to obtain the drag coefficient and downforce coefficient of the car.
... Shadmani, et al. [18] experimentally demonstrated that drag force of Ahmed body with plasma actuator system situated in the center of the rear slant surface can be decreased by 3.65% and 2.44% in steady and un steady actuations respectively. Additionally, the impact of ground clearance had been studied a lot as in [19][20][21][22][23][24][25][26] The impact of car modification on reducing the drag had been investigated a lot in terms of changing the shape of the geometries utilizing different turbulence model. The baseline model in this study is Ahmed body, as the most famous geometry in aerodynamic of road vehicles. ...
In overall car performance and ride stability, external car aerodynamic study is of great importance, making it a key element in effective automobile design. In this study, the effect of the vehicle's length on the drag coefficient was numerically investigated. For this purpose, a CFD analysis based on RANS turbulence models was carried out for six configurations for the Ahmed body model with different length in addition to the baseline model. Tetrahedral cells were adopted throughout air enclosure except some prism cells around the vehicle's surfaces. Good agreement for the benchmark model was obtained by comparing current numerical results with experimental related data. The numerical results demonstrate that 1244mm is the optimal length of the Ahmed body. Increasing the overall length of the Ahmed body by about 19.15% leads to decreasing drag coefficient by 8.95%.
... Similarly, the ultimate goal of the F1 cars is to reduce the total time of a lap. Due to the sensitive operation conditions such as close ground proximity, a marginal difference of the aerodynamic performance caused by the ride height change would have an impact on the final lap time [57]. Thus, investigation of the aeroelastic behaviour of a double-element composite wing using the FSI modelling discussed in this research work is crucial to enhance accuracy of the wing performance associated with the complex fluid flow field. ...
This research paper focuses on a novel coupling of the aerodynamic and structural behaviour of a double-element composite front wing of a Formula One (F1) vehicle, which was simulated and studied for the first time here. To achieve this goal, a modified two-way coupling method was employed in the context of high performance computing (HPC) to simulate a steady-state fluid-structure interaction (FSI) configuration using the ANSYS software package. The front wing plays a key role in generating aerodynamic forces and controlling the fresh airflow to maximise the aerodynamic performance of an F1 car. Therefore, the composite front wing becomes deflected under aerodynamic loading conditions due to its elastic behaviour which can lead to changes in the flow field and the aerodynamic performance of the wing. To reduce the uncertainty of the simulations, a grid sensitivity study and the assessment of different engineering turbulence models were carried out. The practical contribution of our investigations is the quantification of the coupled effect of the aerodynamic and structural performance of the wing and an understanding of the influence of ride heights on the ground effect. It was found that the obtained numerical surface pressure distributions, the aerodynamic forces, and the wake profiles show an accurate agreement with experimental data taken from the literature.
... In the auto-racing industry, the characterisation of complex vortex fields is key for enhancing car performance (e.g. Zhang et al. 2006). ...
The ability to track vortices spatially and temporally is of great interest for the study of complex and turbulent flows. A methodology to solve the problem of vortex tracking by the application of machine learning approaches is investigated. First a well-known vortex detection algorithm is applied to identify coherent structures. Hierarchical clustering is then conducted followed by a unique application of the Hungarian assignment algorithm. Application to a synthetic flowfield of merging Batchelor vortices results in robust vortex labelling even in a vortex merging event. A robotic PIV experimental dataset of a canonical Ahmed body is used to demonstrate the applicability of the method to three-dimensional flows.
Graphic abstract
... Using comments from Nishino et al. [12,13], Bimbato et al. [10] successfully adopted a configuration of fixed ground with no vorticity generation on it to simulate the moving ground effect. The applicability of the blockage effect in aerodynamic models was discussed by Zhang et al. [18] and Cui and Zhang [19]. ...
A purely Lagrangian vortex method is employed to investigate turbulent flows past a rough circular cylinder under moving wall effect at large-gap regime, namely h * /d * = 0.45 and 0.80 (h * establishes the gap height between the moving wall base and the cylinder underside, and d * defines the outer cylinder diameter), yielding data in a transition regime, between the supercritical and transcritical regimes. In the large-gap regime, strong vortical structures are cyclically generated at the rear part of the cylinder. The numerical simulations utilize a two-dimensional model to simulate surface roughness effect. That model is inspired in a point set strategically located close to a body surface to inject momentum in its boundary layer and thus to capture a delay in the separation point of flow. Special attention is directed toward the relative roughness size variation, being that each test case always starts from an upper-subcritical Reynolds number of Re = 1.0 × 10 5. The present work contributes in the literature: (i) providing a detailed study of temporal evolution of pressure distribution, simultaneously computed with the integrated aerodynamic loads (drag and lift forces), Strouhal number and angle of boundary layer separation and (ii) examining the possibility of predicting suppression of vortex shedding. Such approach has been successfully applied within the study of bluff body aerodynamics at small-gap regime (i.e., h * /d * < 0.25), where the vortex shedding frequency completely disappears. Overall, the results reveal the sensitivity of the numerical technique to capture changes on the aerodynamic characteristics of a cylinder. For test with the rougher cylinder at h * /d * = 0.45, the big and small peaks on the drag curve are more influenced by increasing of noises because of surface roughness effect; consequently, the drag curve oscillates around small values reducing the mean drag coefficient. A drag reduction around 13% is identified as compared to a smooth cylinder. The lift force also reduces and still remains positive. The position of the separation points of the flow also changes, which characterizes boundary layer detachment with delay. The results are substantiated by a greater base pressure of the rougher cylinder; furthermore, only small differences are identified in the base pressure between both smooth and less rough cylinders, which explains the nearly constant level of drag force on them.
An automotive diffuser is an open channel within the underbody of a vehicle that features a diverging ramp in the aft section. The performance of a diffuser is sensitive to ground effect where decreases in ride height result in increases in downforce. However, below a critical value, any further reduction in ride height results in a significant loss of downforce. Previous experimental investigations demonstrated that the dominant flow feature within underbody diffuser flows is a pair of counter-rotating longitudinal vortices, and the resulting downforce behavior is directly linked to the structure of the longitudinal vortex pair. This study investigates the effect of ride height on the behavior of the longitudinal vortex pair within an underbody diffuser flow in ground effect. The unsteady flow past a diffuser-equipped bluff body with a 17-degree diffuser ramp angle is simulated using large eddy simulation with wall-stress modeling, commonly referred to as wall modeled large eddy simulation (WMLES). The flow Reynolds number based on body length is 1.75 million. Numerical simulations are performed with OpenFOAM and WMLES is implemented with libWallModelledLES, a third-party WMLES library for OpenFOAM. Results show that the mean center-line surface pressure distributions along the underbody match well with experiments. Visualization of the vortices with isosurfaces of the Q-criterion demonstrates that the longitudinal vortices experience a spiral-type vortex breakdown which propagates upstream with decreasing ride height.
Purpose
Aerodynamics plays a crucial role in enhancing the performance of race cars. Due to the low ride height, the aerodynamic components of race cars are affected by ground effects. The changes in pitch and roll attitudes during the car’s movement impact its ride height. This study aims to analyze the aerodynamic characteristics of race cars under specific pitch and roll attitudes to understand the underlying aerodynamic mechanisms. This paper focuses on the aerodynamic characteristics of racing cars under variations in body posture associated with different vehicle ride heights. It examines not only the force and pressure distribution resulting from changes in the overall vehicle posture but also the flow field behavior of both surface flow and off‑body flow. Analyzing individual components reveals the impact of the front wing on the overall aerodynamic performance and aerodynamic balance of the racing car under these posture variations.
Design/methodology/approach
The grid strategy for the computational fluid dynamics (CFD) method was established under baseline conditions and compared with the results from wind tunnel experiments. The CFD approach was further employed to investigate the aerodynamic characteristics of the racing car under varying body postures associated with different vehicle ride heights. Emphasis is placed on the overall aerodynamic performance of the vehicle and the various components’ influence on the changing trends of aerodynamic forces. By considering the surface pressure distribution of the car, the primary reasons behind the changes in aerodynamic forces for each component are investigated. In addition, the surface flow and detached flow (wake and vortex distributions) of the car were observed to gain insights into the overall flow field behavior under different attitudes.
Findings
The findings indicate that both pitch and roll attitudes result in a considerable loss of downforce on the front wing compared with other components, thereby affecting the overall downforce and aerodynamic balance of the vehicle.
Originality/value
This paper focuses on the aerodynamic characteristics of racing cars under variations in body posture associated with different vehicle ride heights. It examines not only the force and pressure distribution resulting from changes in the overall vehicle posture but also the flow field behavior of both surface flow and off-body flow. Analyzing individual components reveals the impact of the front wing on the overall aerodynamic performance and aerodynamic balance of the racing car under these posture variations.
This article presents the results of an experimental investigation into the impact of rake, or inclination of the underfloor, on the aerodynamics of a bluff body equipped with an underbody diffuser. An extensive wind tunnel campaign, utilising a remotely-actuated model for faster data acquisition, showed that introducing rake results in a downforce increase at all ride heights and diffuser angles, with the strongest effect occurring at low ride heights. Surface pressure measurements on the underbody revealed this to be caused by three main effects. Firstly, a large increase in loading at the front of the floor, due to the inclination of the floor with rake angle and subsequently an increase in the pressure pumping effect. Secondly, a reduction in the suction peak at the throat of the diffuser, which leads to reduced pressure recovery in the diffuser, and less likely separation at high diffuser angles or low ride heights. Thirdly, stronger streamwise vortices along the edges of the underfloor and diffuser, which generate downforce directly due to their low-pressure cores, but also introduce upwash under the model, further inhibiting separation in the diffuser. As the related drag penalty is minimal, aerodynamic efficiency is also improved with increasing rake angle.
This extended essay investigates the optimal angle of attack for the front wings of Formula 1 cars to maximize aerodynamic efficiency. Utilizing SOLIDWORKS Flow Simulation, the study models a multi-element front wing to analyze the effects of varying angles from 0° to 18°. The research explores the interplay between lift, drag, and the lift-to-drag ratio, identifying 11° as the most efficient angle, providing the highest downforce with minimal drag. These findings offer valuable insights into optimizing F1 aerodynamics, contributing to advancements in motorsport performance.
This investigation proposes a novel LPT facility featuring Helium-Filled Soap Bubbles flow tracers, LED illumination and two high-speed cameras to characterize the dominating flow patterns within automotive underbodies. A remote control (RC) car model, fitted with custom-made floor and diffusers, traverses a region of seeded air following the Ring of Fire methodology. Underground-placed cameras view the car through a transparent panel, providing unparalleled optical access to the underbody of the car. The on-site measurement setup and the interaction between car model and ground enhance the realism and fidelity of the experiments, while potentially reducing testing costs associated with wind tunnel operation. The setup is shown to be a valid alternative to conventional testing approaches to capture flow separation, 3D flow evolution and differences in the flow field between the four tested configurations, whereby the diffuser angle was varied in the range between 5° and 20°. The 15° diffuser led to the largest velocity and pressure peaks under the car, whereas the 10° diffuser produced the most downforce thanks to the diffuser “pumping” effect, leading to a large region of low pressure under the vehicle. Notably, the 20° diffuser featured the most prominent flow separation at the diffuser’s leading edge, heavily affecting its ability to sustain low pressures under the car. The results show that the wide tyres have a major impact on the underbody flow, because their large wakes induce mass flow leakage through the sides of the car, thus disrupting the mechanism of downforce generation and impairing the generation of streamwise vortices.
In this paper, the ground boundary condition was studied for static ground effect (SGE) of a non-slender delta wing with sweep angle of 45 degree in a low-speed wind tunnel at Reynolds number of considering static ground condition with a fixed flat plate and dynamic ground condition with a moving belt mechanism. The static ground condition was further simulated with the Belt Off condition, where the tunnel floor represented the ground, hence static ground effect was demonstrated with three different fidelity levels. The characterization of different ground boundary conditions was accomplished using force measurements considering the aerodynamics and the longitudinal static stability of the wing. The results indicate that dynamic ground condition results in larger area under the lift-to-drag ratio versus angle of attack curve compared to out of ground cases rather than increased peak values observed for the static ground condition. Belt On and Belt Off cases resulted in reduced slopes for the aerodynamic coefficients compared to the static ground condition, which resulted in different aerodynamic center positions on longitudinal axis. Dynamic pressure loss and flow angularity changes due to the ground boundary condition might be the driving mechanisms for the altered stability characteristics.
A simulation-based study of three different types of front wing designs used in modern Formula 1 cars was done. The study mainly focuses on the aerodynamic forces that a Formula One car generates mainly the Downforce, the Drag force, & the Lateral force at low cornering speeds. These forces were studied in detail & taking a closer look at how they migrate during the dynamic conditions the car is thrown at various Side Slip (Yaw) Angles, these results were compared with the wing Scuderia Ferrari used in the 1998 formula 1 championship to better understand the inherent problems faced in those previous designs. A brief study of the flow field & flow lines was conducted along with the vortex generation for all three wings. Vortex formation and management is a prominent part of research being carried out for a formula 1 car, so a brief study on the phenomenon of vortex generation & Y250 vortex formation was also carried out. The studies were carried out over typical medium-speed corners where the speed ranges between 150-220 KM/Hr. A study on the effect of the flow field of the top element on the lower element was carried out where the 5th element was removed from each of the three wings & the effect on the downforce & drag value was analysed along with the pressure field. Keywords: Modern formula 1, Front wing designs, Cornering speeds, aerodynamic forces, Side Slip (Yaw) Angles, Centre of pressure (CoP), Lateral force, CFD, Downforce
The diffuser is a critical component in sports cars, enhancing aerodynamics by increasing downforce and reducing drag. Previous studies have focused on its dependence on diffuser incidence, height, and base pressure. The design of the car, particularly the rear end shape and the rear wing's presence, affect base pressure and the diffuser's performance. Previous studies have investigated the effects of diffuser geometry on aerodynamic performance, but the current study is the first to examine the relationship between the diffuser and the rear tires. It also provides specific and quantitative results on the impact of different diffuser design parameters on drag and downforce. The relationship between the rear tires and the double-element inverted wing diffuser using computational fluid dynamics (CFD) was investigated. This is an essential problem because the diffuser is a critical component of sports cars, and its design can significantly impact aerodynamic performance. CFD was used to simulate the flow of air around the car model. The CFD model was based on the Nissan Sunny (Versa) type Almera design, and the diffuser main element and flap wing angles were set at 4 and 15.5°, respectively. The flap gap, overlap distance, and wing ride height above the ground were varied to achieve an optimal aerodynamic design. The study found that the wing's ride height significantly influences the flow through the diffuser. The diffuser significantly impacts base pressure and downforce production. Increasing the ride height decreases base pressure, leading to an increase in downforce until a specific point near the car body, where downforce further increases. The study concluded that the best double-element diffuser design was selected based on lift-to-drag results and the allowable dimensions of the car, wing ride height, element gap, and overlap distances. Ultimately, the best diffuser wing design features a ride height of 154 mm, a gap distance of 10 mm, and an overlap of 5 mm. This design reduces drag by approximately 2.7 % and remarkably increases downforce ten times compared to the baseline car model.
Present paper aims to assess the performance and limits of boundary element method for the reliable simulation of ground effect phenomena on hydrodynamic lifting surfaces. Benefitting from the ground effect, especially in extreme ground proximity, suggests a promising concept for lifting bodies. On the other hand, the more pronounced the ground effect, the more complicated flow physics it exhibits, making the problem harder to handle numerically. In this study, a potential-based boundary element method (BEM) is applied to the flow past a 3D rectangular wing within a wide range of ground clearances corresponding to out of ground effect (OGE), in ground effect (GE) and extreme ground effect (EGE) conditions. Both positive and negative angles of attack are tested to examine the lift and downforce producing cases. The potential flow around the airfoil is computed using the mixed constant-strength source and constant-strength dipole based panel method. The results show that BEM successfully predicts the lift force variation for a wing working in ground proximity (GE). However, approaching the bounds of extreme ground effect is seen to introduce a progressive decrease of the fidelity of the method. A similar tendency is observed in the downforce generating conditions, which is also an important scenario for ground vehicle aerodynamics. BEM remarkably overestimates the magnitude of the downforce when the ground clearance reaches up to the EGE conditions, still, it produces quite satisfactory results for the rest of the tested configurations. The pressure distributions are also provided to examine the flow field in the aforementioned cases. Overall, the results lead us to conclude that BEM stands as a robust and reliable prediction tool for ground effect on 3D wings but the extreme ground effect condition represents the limit of its accuracy range.
A simulation-based study of three different types of front wing designs used in modern Formula 1 cars was done. The study mainly focuses on the aerodynamic forces that a Formula One car generates mainly the Downforce, the Drag force, & the Lateral force at high cornering speeds. These forces were studied in detail & taking a closer look at how they migrate during the dynamic conditions the car is thrown at various Side Slip (Yaw) Angles, these results were compared with the wing Scuderia Ferrari used in the 1998 Formula 1 championship to better understand the inherent problems faced in those previous designs. A brief study of the flow field & flow lines was conducted along with the vortex generation for all three wings. Vortex formation and management is a prominent part of research being carried out for a Formula 1 car, so a brief study on the phenomenon of vortex generation & Y250 vortex formation was also carried out. The studies were carried out over typical high-speed corners where the speed ranges between 220-300 KM/Hr. A study on the effect of the flow field of the top element on the lower element was carried out where the 5th element was removed from each of the three wings & the effect on the downforce & drag value was analysed along with the pressure field. Keywords: Modern formula 1, Front wing designs, Cornering speeds, aerodynamic forces, Side Slip (Yaw) Angles, Centre of pressure (CoP), Lateral force, CFD, Downforce
A simulation-based study of three different types of front wing designs used in the modern Formula 1 cars was done. The study mainly focuses on the aerodynamic forces that a Formula One car generates mainly the Downforce, the Drag force, & the Lateral force at low cornering speeds. These forces were studied in detail & taking a closer look at how they migrate during the dynamic conditions the car is thrown at various Side Slip (Yaw) Angles, these results were compared with the wing Scuderia Ferrari used in the 1998 formula 1 championship to better understand the inherent problems faced in those previous designs. A brief study of the flow field & flow lines was conducted along with the vortex generation for all three wings. Vortex formation and management is a prominent part of research being carried out for a formula 1 car, so a brief study on the phenomenon of vortex generation & Y250 vortex formation was also carried out. A test on ride height and vorticity was also studied when the ride height was varied and the values were analysed. A study on the effect of the flow field of the upper element on the lower element was carried out where the 5th element was removed from each of the three wings & the effect on the downforce & drag value was analysed along with the pressure field.
Aerodynamics has become the dominant competitive factor in high-performance racing. This section introduces the most important parameters for describing the aerodynamic properties of a vehicle and explains their influence on driving dynamics. With the help of these parameters, the dimensions in which the aerodynamic behavior of a racing vehicle differs from that of a production vehicle are clarified. In the further course of the chapter, the function and interaction of the aerodynamic components of a racing vehicle are described.
Modern sports vehicles got enhanced in terms of performance by using better tools to design and analyze. The study of aerodynamics has always been a very intense, challenging as well as exciting task for professionals working on the research and development. This work presents the numerical analysis of our modeled race car aerodynamics and the simulation on it. We have studied different airfoils and used them in the rear wing. We studied the air flowover the body of the car at different velocities and its effect on the various aerodynamic parameters of the car, i.e., downforce/negative lift, stress, pressure and drag. We collected and tried to study what the numbers meant and analyzed the data which we got from the simulation solver. This was a tricky and time-consuming part as simulation has much to study and understand. Our aim was to get meaningful results from our simulation study. Our simulation study was without aero kit and with aero kit. In the following International Journal of Scientific Research in Engineering and Management (IJSREM) Volume: 07 Issue: 01 | January - 2023 Impact Factor: 7.185 ISSN: 2582-3930 © 2023, IJSREM | www.ijsrem.com DOI: 10.55041/IJSREM17557 | Page 2 sections we will further discuss and explain more in detail. Final conclusion of this project will be; to find outthe best fit airfoil and most efficient placement (angle of attack & height) of it in the rear of our modeled car. In this project we have designed a car, studied air flow over the body of the car at different velocities and its effect on the various aerodynamic parameters of the car i.e., downforce/negative lift, stress, pressure and drag.
In this paper, the effect of ground on aerodynamics and longitudinal static stability of a non-slender delta wing with sweep angle of 45 degree and thickness-to-chord ratio (t/c) of 5.9% was characterized at Reynolds number of 9×104 in a low-speed wind tunnel using force and pressure measurements. The measurements were conducted for angles of attack varying between 0≤α≤30 degrees and non-dimensional heights between 3%≤h/c≤107% and height stability of the wing based on aerodynamic center in pitch (Xa) and aerodynamic center in height (Xh) was constructed. The results indicate that the effect of ground has substantial impact on both aerodynamic performance and stability of the delta wing. As the height of the wing decreases, both drag and lift forces increases where these effects were observed to be more pronounced for higher angles of attack. The maximum aerodynamic performance with increasing ground effect intensity was measured around 7 degree. Center of pressure (Xp) as well as Xa travel in a limited range over the wing chord, whereas Xh exhibits back and forth movement on the longitudinal axis resulting in interchanging stability characteristics varying with both height and angle of attack. The pressure measurements showed that the effect of ground has significant and complex impact on both vortex reattachment and vortex strength with varying angles of attack and heights such that it might promote reattachment and increases vortex strength but might cause earlier stall.
The aerodynamic effect plays a major role in the fuel efficiency and stability of the vehicle. The contact patch loads between the tire and road also play a vital role in the stability and fuel efficiency and are directly related to the vehicle load. In this research, lift force generated because of an additional wing attached to the car is studied. While the vehicle moves around 40–130 kmph. Upward vertical lift force produced from aerodynamics reduces the weight of the car virtually. The wing or airfoil is attached to use the gap between the car’s top surfaces to the lower surface of the wing to cause a Venturi-like effect. Lightweight car will be able to make more efficient use of its tires than a heavier car. Computational fluid dynamics (CFD) analyses are done with ANSYS Fluent. The validation of airflow characteristics, lift and drag forces from simulations, is done with data from wind tunnel testing. The study was carried out by varying parameters such as height between the upper surface of the car and the lower surface of the wing, and wingspan. The result obtained shows that the weight of the car can be reduced by 11% virtually with the wing forces, and the payload could increase by 11% or improve the fuel efficiency by 10–15%.KeywordsAerodynamicsTire/roadCar-wingDragLiftNozzle effect
Generating aerodynamic downforce for the wheels on the front axle of a car is a much more difficult task than for the rear axle. This paper, submitted to the special issue of Energies “Future of Road Vehicle Aerodynamics”, presents an unusual solution to increase the aerodynamic downforce of the front axle for cars with covered wheels, with the use of an elastic splitter. The effect of the inflatable splitter on the aerodynamic forces and moments was studied in a DrivAer passenger car and a fast sports car, Arrinera Hussarya. Providing that the ground clearance was low enough, the proposed solution was successful in increasing the front axle downforce without a significant increase in drag force. The possibility of emergency application of such a splitter in the configuration of the body rotated by up to 2 degrees with the front end raised was also analyzed. An elastic, deformed splitter remained effective for the nonzero pitch case. The results of the calculations are presented in the form of numerical data of aerodynamic forces, pressure and velocity distributions, and their comparisons. The benefits of the elastic splitter are documented, and the noted disadvantages are discussed.
The numerical simulations are employed to study the propulsive characteristic of travelling wave foil under various ground distances and non-dimensional motion frequencies (St number). This study concentrates on ground wall's effect on travelling wave foil's propulsive property and the research object contains both the two dimensional (2D) and three dimensional (3D) models. A finite-volume method is employed to simulate the flow field by using of the commercial software ANSYS Fluent and the dynamic grid technique, coupled with the User Defined Function (UDF), is utilized to realize the foil's travelling wave motion. The calculation results demonstrate that the ground wall produces great impact on travelling wave foil's fluid dynamics. In specific, the thrust force will be enhanced under high St number and the drag force will be reduced when it comes to low St number. As for the propulsive efficiency, there also exists distinct increase. At the same time, the symmetry along the vertical direction of the flow field is destroyed, leading to the pretty high lift force. Flow analyses have demonstrated that the surface pressure of the travelling wave foil presents sharp increase under the existence of the wall and the vortex structure have also undergone huge change. Insights from current study will be beneficial for the future design of bionic underwater vehicle.
A discrete vortex method is implemented with a hybrid control technique of vortex shedding to solve the problem of the two-dimensional flow past a slightly rough circular cylinder in the vicinity of a moving wall. In the present approach, the passive control technique is inspired on the fundamental principle of surface roughness, promoting modifications on the cylinder geometry to affect the vortex shedding formation. A relative roughness size of ε*/d* = 0.001 (ε* is the average roughness and d* is the outer cylinder diameter) is chosen for the test cases. On the other hand, the active control technique uses a wall plane, which runs at the same speed as the free stream velocity to contribute with external energy affecting the fluid flow. The gap-to-diameter varies in the range from h*/d* = 0.05 to 0.80 (h* is the gap between the moving wall and the cylinder bottom). A detailed account of the time history of pressure distributions, simultaneously investigated with the time evolution of forces, Strouhal number behavior, and boundary layer separation are reported at upper-subcritical Reynolds number flows of Re = 1.0 × 105. The saturation state of the numerical simulations is demonstrated through the analysis of the Strouhal number behavior obtained from temporal history of the aerodynamic loads. The present work provides an improvement in the prediction of Strouhal number than other studies no using roughness model. The aerodynamic characteristics of the cylinder, as well as the control of intermittence and complete interruption of von Kármán-type vortex shedding have been better clarified
Studies the flow underneath two types of 'ground effect' vehicles, plenum and venturi, noting application to racing car design. Discusses the differences between plenum and venturi flow noting the longitudinal vortex pair characteristics of the latter. A low speed wind tunnel was used to test the plenum and venturi models, and for some tests a moving belt ground plane was used. Presents results of pressure profile for the plenum model, noting importance of the inside pressure as a determinant of lift and drag. Shows how plenum pressure (nearly uniform) depends on relative gap sizes in high or low external pressure regions. Discusses static pressure distribution, flow visualization and lift/drag coefficient results for the venturi model. Examines how the lift and pressure distribution changed with modifications to the venturi model. (C.J.U.)
This paper discusses some aspects of the aerodynamics of Year-2000 Formula-One racing cars. It presents an overview of the role of the F1 aerodynamicist, including testing techniques, model design, and data analysis. The effects of front and rear wing changes are discussed. Generic results are presented that illustrate how changes in ride height through a corner affect the aerodynamics, and hence the handling of the racecar.
In recent years the remarkable performance of the Grand Prix car has been strongly influenced by aerodynamic design. Since the introduction of the current racing regulations the varied approaches to aerodynamic design have converged and to the casual observer current Formula ***I cars appear to be almost identical. This paper examines the aerodynamic considerations that have led to these designs.
A numerical technique was developed to investigate the performance of automotive lifing surfaces in close proximity to the ground. The model is based on the Vortex Lattice Method and this includes freely deforming wake elements. The ground effect was simulated by reflection and both steady and unsteady pressures and loads on various wing planforms were considered. Calculated results are presented for wings having both positive and negative incidences, with and without ground effect. Also the transient lift of a wing in a plunging motion was analyzed in ground proximity and at a negative angle of attack. Finally the periodic lift fluctuations on the front winglet of a racing car, due to its suspension oscillations, were calculated and found to exceed approximately twice the steady state value. (A)
Results are presented from an experimental study of the lift, drag, pitching moment, and flow field of a series of rounded edge simple bluff bodies of various cambers and tapers. The bodies were proportioned to be similar to those of idealized ground vehicles such as automobiles, vans, and trucks. The models were tested with and without simulated wheels, underbody roughness, and proximity to a stationary and moving ground plane. The pitch angle was varied at zero yaw angle. The force and moment coefficients and flow visualization studies indicated the existence and importance of flow regimes characterized by a pair of trailing vortices on the leeward side of the body similar to those found over an inclined body of revolution and over slender delta wings. These flows can suppress bubble-type separation. The effects of a rough underbody are generally detrimental although less so if the rough surface is on the windward side. A moving ground plane was found to give significantly different lift and drag for small ground clearances characteristic of actual road vehicles.
A practical application of two-dimensional subsonic bluff body flow research can be seen in the design, construction and positioning of tall slender buildings. Similarly, from a three-dimensional viewpoint, drag reduction and vortex control is an important factor in the latest road vehicle designs. From just these two examples it can be seen that the problem of flow about a bluff body is one of major practical importance, while at the same time being of great theoretical interest. However, despite many years of extensive testing, there has been little progress made on the theoretical investigation of turbulent base flows since the foundations laid down by Kirchhoff and von Karman. The non-steady processes in the wake, in particular the complex dynamics of vortex formation, have proved to be problems of formidable size.
The aerodynamics of wings in ground effect has been studied using experimental and computational methods. Wind tunnel tests were used to quantify the effect of the ground on the aerodynamic performance of a wing, with the suction surface nearest to the ground. Features of the flowfield around the wing were investigated using Laser Doppler Anemometry and Particle Image Velocimetry to map the wake at the centre of the wing, and the state of the tip vortex. Initially, a single element configuration was used, both under transition free and transition fixed conditions. The application of Gurney flaps was then examined. The experimental study was completed using a double element configuration. The performance is discussed together with the flowfield results. Wind Tunnel testing was performed at a Reynolds number of approximately 0.75x10(6) based on the chord of the double element wing. The application of a computational technique has been examined using a Reynolds averaged Navier Stokes solver. Trends in the aerodynamic performance of a single element aerofoil in ground effect were predicted well using a Spalart-Allmaras turbulence model.
Wind tunnel tests were carried out with a full-scale passenger car over a moving belt. The suspension system of the vehicle was redesigned in such a way that drag and lift forces could be measured whilst the wheels were rolling on the moving ground. The measurements were carried out with an internal balance installed inside the vehicle. Additionally, total-pressure-deficit contour plots were reduced from wake-rake measurements behind the front and rear wheels in order to identify the origin of different bound vortices generated at the wheels. It was found from these tests that rolling wheels have a large aerodynamic influence on passenger cars. They decrease the drag and increase the lift forces in comparison to fixed wheels. This has been established in an absolute and a relative sense by investigating different vehicle configurations. (A)
Performance data and flow characteristics for subsonic, two-dimensional, straight center line diffusers are presented. The four primary flow regimes which can occur are described and presented as functions of overall diffuser geometry. The performance of both stalled and unstalled diffusers is mapped for a wide range of geometries and inlet boundary layer thicknesses. An understanding of the relationships between flow regime and performance leads to a rational basis for diffuser design. The important maxima of performance and their location on the performance maps are presented. Both the range of data and correlations of optima of performance are extended beyond previous results.
A computational study has been performed in order to model the flow around an inverted aerofoil in ground effect. The method used is solutions of Reynolds-aver aged Navier-Stokes equations with turbulence modelled by Spalart-Allmaras model and ko; model. The results are compared to measured surface pressures and LDA results taken at the centre of a wing in ground effect. Major features of the flow are captured. The results yield good qualitative trends for the aerodynamic performance, using the one-equation model when the surface pressures are compared at different heights. In general, the wake thickness is predicted reasonably well in the region near to the trailing edge. Further downstream, the wake is predicted to be thicker than that found in the experiments, with reduced velocities. The ground boundary layer is predicted well using the one-equation model, but is significantly too thick using the two-equation model.
The purpose for this effort was to investigate the likely performance enhancement of industrial fan blade
designs by utilizing Gurney flaps. A two–dimensional linear cascade was established to test various
Gurney flap configurations. For the aerodynamic analysis, the Navier–Stokes equations were solved
using a high resolution approximate Riemann solver utilizing the Baldwin and Lomax turbulence model.
Two baseline geometries were tested, one had a sharp trailing edge and the other had a rounded trailing
edge. Comparisons were made between the baseline configurations and configurations with various
sized Gurney flaps. Performance data was collected, the flowfields were interrogated, some geometry
modifications were made, and a conclusion drawn regarding the flap size most likely to produce a performance
gain.
In the last fifteen years aerodynamics has made a significant contribution to the major changes in the configuration and performance of Formula One racing cars. Tripling the negative lift has affected the design of all major components and has altered the requirements of vehicle dynamics. The magnitude of the negative lift available, and the promise of future developments, has so affected the cornering and braking accelerations, and hence cornering speeds, that changes are now necessary to limit performance. It is essential to the technical future of Formula One that these changes do not inhibit the development and technology that may, in time, benefit the development of road vehicles as a whole.
The method of R. H. Liebeck and A. M. O. Smith (1973) has been extended to study the optimization of multielement airfoils, and the preliminary designs obtained thus far appear promising. This paper describes some of the development and testing of optimized airfoil designs at Douglas over the past 10 years. Included are example solutions and wind-tunnel test results, together with the results from some applications. At several points, recommendations for further and/or more detailed studies are offered.
The influence of edge vortices generated by a generic double-element wing on force behaviors are discussed. The wing is equipped with end plates and operates in ground effect. The downforce-vs-height curve is divided into three distinct regions according to ground proximity and flap setting. As the wing is moved from a height in freestream
to the ground plane, the downforce first experiences a rapid enhancement (region A). This process is accompanied by the presence of a concentrated vortex off the edge of the side plate and diffuser effect of the wing. At a critical height, the vortex breaks down and its contribution to the downforce is lost. This creates a change in the gradient of
the downforce slope. The force enhancement process continues as the height of the wing is reduced (region B); the
main diffuser effect is still present. The downforce is lost below a height where the maximum downforce is reached,
due to large separation on the wing (region C). The importance of the edge vortices in defining the characteristics
of the downforce curve is established.
The effect of Gurney naps on two-dimensional airfoils, three-dimensional wings, and a reflection plane model were investigated. There have been a number of studies on Gurney flaps in recent years, but these studies have been limited to two-dimensional airfoil sections. A comprehensive investigation on the effect of Gurney flaps for a wide range of configurations and test conditions was conducted at Wichita State University. A symmetric NACA 0011 and a cambered GA(W)-2 airfoil were used during the single-element airfoil part of this investigation. The GA(W)-2 airfoil was also used during the two-element airfoil study with a 25% chord slotted flap deflected at 10, 20, and 30 deg, Straight and tapered reflection plane wings ,vith natural laminar flow (NLF) airfoil sections were tested for the three-dimensional wing part of this investigation. A fuselage and engine were attached to the tapered NLF wing for the reflection plane model investigation. In an cases the Gurney flap improved the maximum lift coefficient compared to the baseline clean configuration. However, there was a drag penalty associated with this lift increase.
An investigation was conducted on the performance characteristics and flowfield phenomena of a wing in ground effect. Model tests were performed in low-speed wind tunnels equipped with moving ground. A highly cambered single element wing, with the suction surface nearest to the ground, nas used to investigate the effect of changing both the ride height from the ground and the incidence. Data obtained in model tests included force balance measurements, surface pressure results, and surface oil flow visualization. Results are compared with the freestream case. As the ride height is reduced, higher levels of downforce were recorded; at clearances between the suction surface and the ground of less than 20% chord, the downforce is significantly higher. Closer to the ground, at a ride height of less than 10% chord, downforce drops as the wing stalls. This force reduction phenomenon is shown to be due to trailing-edge separation of the boundary layer, The effect of transition fixing was found to be significant, especially in terms of levels of downforce generated in ground effect.
An investigation of a cambered, double-element, high-lift wing operating in ground effect was performed. The effect of ground proximity and flap setting was quantified in terms of aerodynamic performance and off-surface flowfield characteristics. From that, it was found that the flow is three-dimensional toward the wing tip with the main element generating most of the downforce but retains quasi-two-dimensional features near the center of the wing. However, at large heights the downforce increases asymptotically with a reduction in height. Then there is either a plateau, in the case of a low flap angle, or a reduction in downforce, in the case of a large flap angle. The downforce then increases again until it reaches a maximum and then reduces with decreasing height above the ground. The maximum downforce is dictated by gains in downforce from lower surface suction increases and losses in downforce caused by upper surface pressure and lower surface suction losses, with a reduction in height. For the high flap angle there is a sharp reduction just beyond the maximum, mainly because of the boundary layer separating, and a resultant loss of circulation on the main element.
The force and pressure behavior of a generic diffuser in ground effect were investigated. The diffuser model is a bluff body with a rear diffuser at 17 deg to the horizontal, and side-plates. Measurements were conducted in a low speed wind tunnel equipped with a moving ground facility. Techniques employed were force balance, pressure taps, and surface flow visualization. The diffuser flow in ground effect was characterized by vortex flow and three-dimensional flow separation. Four types of force behavior were observed: (a) down-force enhancement at high ride heights characterized by an attached symmetric diffuser flow, (b) maximum down-force at moderate ride heights characterized by a symmetric diffuser flow and separation on the diffuser ramp surface, (c) down-force reduction at low ride heights characterized by an asymmetric diffuser flow and flow separation, and (d) low down-force at very low ride heights, also characterized by an asymmetric diffuser flow and flow separation. The down-force reduction near the ground is attributed to flow separation at the diffuser inlet and subsequent loss of suction in the first half of the diffuser.
This study investigates the effects of various ground clearances (h/D=0.14, 0.2, 0.5, 1.0), as well as the type of ground (stationary or moving ground plane), on the flow around a variety of two-dimensional bluff bodies. The measured base pressures with or without a moving ground were almost identical, suggesting that the drag remains almost constant. However, significant changes in the lift forces were observed when the ground plane was moving. The difference in pressure distribution between the top and bottom of the model increases as the ground clearance is reduced. This phenomenon is exaggerated with the introduction of a moving ground which concludes that larger lift forces and longer wakes are apparent with decreasing clearance. The measurement of Strouhal number show that the low ground clearance dampens the periodic flow behind the models, the effect is intensified with a moving ground plane. A comparison of the results with those of the flow around a two-dimensional car model (h/D=0.14, 0.2) underline the dependence of the results on the model geometry.
The use of a moving ground plane is an established wind tunnel technique for ground simulation in surface vehicle tests. However, the data available relating to the influence of variations in ground plane boundary layer thickness on bluff body flowfields is limited. Results from a short series of wind tunnel tests, using a moving ground facility, are presented, in which mean base pressure measurements are made on three simple bluff body models while; (i) the moving ground speed, relative to the freestream speed, and (ii) the model ground clearance, are varied. The results show that reducing the moving ground speed has a similar effect on the base pressure to a reduction in the model ground clearance. This effect on base pressure is limited to moving ground speeds less than those which result in a significant increase in the ground boundary layer displacement thickness, except in the case of a more complex tandem module body. The data for this model, chosen to simulate a typical cab-container commercial vehicle, suggest that the presence of a gap between the front and rear modules increases significantly the sensitivity of the base pressure to the moving ground speed. Data from this limited study may be useful when comparing measurements made on vehicles with particularly small ground clearances above fixed and/or moving ground planes. They may also serve as a guide to the assessment of the tolerance of a moving ground system to belt speed variations in terms of the ground boundary layer displacement thickness.
Aerodynamic design has become more and more important in the development of modern road and rail vehicles. Therefore, in wind tunnel testing, it is necessary to reproduce the natural conditions on a vehicle as exactly as possible. This paper reports on the effect of ground simulation on vehicle aerodynamics. It is shown that the only accurate simulation technique is the moving ground simulation.The ground effect was investigated with a simple body of two lengths for different ground clearances over a moving belt and a fixed plate. The aerodynamic forces were measured using a six-component balance. For selected parameter configurations, velocities of flow around the body were also obtained. It was found that for small ground clearances especially, the ground simulation has a strong influence on the flow field, resulting in significant effects on the aerodynamic lift and drag.
A moving belt simulation of ground effect is necessary for tests in wind tunnels of road vehicle models. This need has been convincingly demonstrated using scale racing car models, scale saloon and sports car models and small scale truck models in a 2.1 × 1.7 m wind tunnel over the last twelve years. The development of new techniques enabled measurement of forces to be made on models with wheels rotating on a moving ground. The requirement for large models to increase Reynolds number and improve the model detail led to the construction of a large 2.4 × 5.3 m moving belt rig in a new 3.5 × 2.6 m wind tunnel. In order to measure forces and pressures on road vehicle models in crosswinds, a technique using yawed models with rotating wheels on a yawed moving ground was also developed.
The off-surface aerodynamic characteristics of a wing in ground effect are investigated using a number of methods including laser Doppler anemometry and particle image velocimetry. The study focuses on two aspects of the flow: turbulent wake and edge vortex. These features are closely associated with the behavior of the aerodynamic force in ground effect. The size of the wake increases in proximity to the ground. A downward shift of the path of the wake is also observed. Discrete vortex shedding is seen to occur behind the wing. As the wing height is reduced, separation occurred on the suction surface of the wing, and the spanwise vortex shedding is found to couple with a flapping motion of the wake in the transverse direction. An edge vortex is also observed off the edge of the end plate of the wing, which contributes to force enhancement and helps to define the force behavior in the force enhancement region. The rate of change in the downforce vs height curve is linked to the strength of the edge vortex. The vortex breakdown signals a slowdown in the force enhancement. When the maximum downforce height is reached, the. edge vortex breaks down completely.