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![Figure 1: Basic concept of actively translating rear diffuser [18].](profile/Anm-Mominul-Mukut/publication/330661575/figure/fig1/AS:731991104290816@1551531687352/Basic-concept-of-actively-translating-rear-diffuser-18_Q320.jpg)
![Figure 3: Positions of blowing jets [19].](profile/Anm-Mominul-Mukut/publication/330661575/figure/fig3/AS:731991104307204@1551531687457/Positions-of-blowing-jets-19_Q320.jpg)
![Figure 13: Sketch of three configurations of VGs [40].](profile/Anm-Mominul-Mukut/publication/330661575/figure/fig4/AS:731991104290817@1551531687501/Sketch-of-three-configurations-of-VGs-40_Q320.jpg)
Due to higher price, limited supply and negative impacts on environment by fossil fuel, automobile industries have directed their concentrations in reducing the fuel consumption of vehicles in order to achieve the lower aerodynamic drag. As a consequence, numerous researches have been carried out throughout the world for not only getting the optimu...
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... instance, it is extensively revealed that the rear flow field of vehicle is influenced by the flow coming out under the vehicles which implies that the rear flow field can be modified by controlling the flow under the vehicles [16,17]. Kang et al. [18] developed a movable under body diffuser as shown in Figure 1 and Figure 2, and numerically investigated that the automobile's aerodynamic drag could be reduced by an average of more than 4%, which would help to enhance the constant speed fuel efficiency by approximately 2% at a range of driving speeds exceeding 70 km/h. ...
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... their studies, twelve slits were arranged in six pairs in which each pair provides blowing and suction as shown in Figure 9 and a drag reduction of 9.5% has been found. The combined control of suction and blowing is seen to be effective on changing the rear window wake structure, in which streamlines of time average flow is separated (without control) and re-attached (with combined control) as shown in Figure 10. Another experimental and numerical studies have been conducted to evaluate the suction and blowing control on drag reduction on an Ahmed body in three different ways namely, (i) only suction, (ii) only blowing and (iii) combination of both control [36]. ...
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... experimental and numerical studies have been conducted to evaluate the suction and blowing control on drag reduction on an Ahmed body in three different ways namely, (i) only suction, (ii) only blowing and (iii) combination of both control [36]. The outcomes show that their combined effect enhances the drag reduction which is shown in Figure 11 and an average of 10% drag reduction is recorded. ...
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... performance of PA has been investigated experimentally on an Ahmed body with 25° slant angle where 10 PAs are used, among of them, 6 PAs are placed on the separation region on the rear wind and four are placed in two-two pairs in the region where two longitudinal vortices are observed from both sides of the rear window [37]. These position of PAs are actually based on the visualization of the topological structures of the skin friction field using oil film which is shown in Figure 12. The research shows that PAs have effective outcomes on suppressing the separation at the rear end of vehicles and 8% drag reduction is obtained. ...
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... extensive experimental studies have been carried out to evaluate the performance of VGs on aerodynamic drag reduction [40]. In this research, three combinations of VGs namely, (i) complete line-22 VGs (ii) 4 VGs on each side (iii) 14 VGs in the centre were used on a modified Ahmed body which is shown in Figure 13. Details of flow structure are captured by PIV and hot-wire anemometry. ...
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... aim of using this type of VG is to avoid additional drag that is arisen from then conventional VGs, as these are attached externally to the vehicle body. A pair of pocket type VGs are placed in the left and right side of the rear roof end of the Low Mass Vehicle (LMV) to evaluate the effectiveness which is shown in Figure 14. The outcome shows that it can reduce the drag of 2.2%. ...
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... effectiveness of VGs are also evaluated numerically on SUV and Ahmed body with a drag reduction of 4.2% and 10%, respectively [44]. On the other hand, an experimental and numerical investigation has been carried out on a sedan car using 3 delta type of VGs at different yaw angles [45], where the middle VG was kept stationary and remaining two were changed with their angle using smaller stepper motor as shown in Figure 15. In the research, a maximum reduction of drag and lift coefficient have been found as 4.53% and 2.55%, respectively. ...
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... spoiler is an external structure attached to the rear end of the vehicles to control the flow at downstream that helps to minimize the turbulence behind the vehicle and also append downward pressure which reduces the lift. The influence of spoiler on vehicle aerodynamics has numerically investigated on a Toyota Eco car model as shown in Figure 16, and it is found that by using this spoiler at a speed of 30 m/s, drag and lift, respectively can be reduced by 5% and more than 100% [47]. ...
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... performance of flaps has been investigated with three different free stream velocities of 20 m/s, 30 m/s and 40 m/s, by placing two flaps on the side edges of the rear slant and two flaps on the top of the rear slant, and hence the reduction of drag has been found as much as 17.6% and 15%, respectively for the two arrangements of flaps [48]. A special type of flap called Automatic Moving Deflector (AMD) taking inspiration from birds had been tested experimentally on an Ahmed body as shown in Figure 17, by which the maximum drag reduction is achieved from the pressure recovery by AMD which is 19% [49]. ...
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... bottom of a Sedan and Wagon had been modified which has an angle at the bottom rear that acts like an underbody diffuser [51]. The performance of underbody diffuser has been tested with varying angles shown in Figure 18. Results from this study showed a potential aerodynamic drag reduction of the sedan car approximately 10%, and the wagon car by 2-3 %. ...
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... investigation has been carried out on an Ahmed body with non-smooth dimpled surfaces on its slant back [56]. The geometry of non-smooth surfaces are shown in Figure 19. In order to maximize the drag reduction performance of the dimpled non-smooth surface, an aerodynamic optimization method based on a Kriging Surrogate model was employed to design the dimpled non-smooth surface. ...
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... of drag reduction by active and passive methods are graphically presented in Figure 20 and Figure 21 respectively. Maximum contribution of drag reduction for different control methods is shown in Figure 22. ...
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... the above analysis, it is seen that the drag reduction for active control system could be as much as 20% by using the pulse jet [31,32] and plasma actuator [39] as shown in Figure 20 and 22. On the other hand, for passive control system, the drag could be decreased to 21.2% by using Flaps [50] as shown in Figure 21 and 22. However, for combined flow control technique, the drag could be reduced as much as 30% by using blowing jets with porous layer [57] as shown in Figure 22. ...
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... instance, it is extensively revealed that the rear flow field of vehicle is influenced by the flow coming out under the vehicles which implies that the rear flow field can be modified by controlling the flow under the vehicles [16,17]. Kang et al. [18] developed a movable under body diffuser as shown in Figure 1 and Figure 2, and numerically investigated that the automobile's aerodynamic drag could be reduced by an average of more than 4%, which would help to enhance the constant speed fuel efficiency by approximately 2% at a range of driving speeds exceeding 70 km/h. ...
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... their studies, twelve slits were arranged in six pairs in which each pair provides blowing and suction as shown in Figure 9 and a drag reduction of 9.5% has been found. The combined control of suction and blowing is seen to be effective on changing the rear window wake structure, in which streamlines of time average flow is separated (without control) and re-attached (with combined control) as shown in Figure 10. Another experimental and numerical studies have been conducted to evaluate the suction and blowing control on drag reduction on an Ahmed body in three different ways namely, (i) only suction, (ii) only blowing and (iii) combination of both control [36]. ...
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... experimental and numerical studies have been conducted to evaluate the suction and blowing control on drag reduction on an Ahmed body in three different ways namely, (i) only suction, (ii) only blowing and (iii) combination of both control [36]. The outcomes show that their combined effect enhances the drag reduction which is shown in Figure 11 and an average of 10% drag reduction is recorded. ...
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... performance of PA has been investigated experimentally on an Ahmed body with 25° slant angle where 10 PAs are used, among of them, 6 PAs are placed on the separation region on the rear wind and four are placed in two-two pairs in the region where two longitudinal vortices are observed from both sides of the rear window [37]. These position of PAs are actually based on the visualization of the topological structures of the skin friction field using oil film which is shown in Figure 12. The research shows that PAs have effective outcomes on suppressing the separation at the rear end of vehicles and 8% drag reduction is obtained. ...
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... extensive experimental studies have been carried out to evaluate the performance of VGs on aerodynamic drag reduction [40]. In this research, three combinations of VGs namely, (i) complete line-22 VGs (ii) 4 VGs on each side (iii) 14 VGs in the centre were used on a modified Ahmed body which is shown in Figure 13. Details of flow structure are captured by PIV and hot-wire anemometry. ...
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... aim of using this type of VG is to avoid additional drag that is arisen from then conventional VGs, as these are attached externally to the vehicle body. A pair of pocket type VGs are placed in the left and right side of the rear roof end of the Low Mass Vehicle (LMV) to evaluate the effectiveness which is shown in Figure 14. The outcome shows that it can reduce the drag of 2.2%. ...
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... effectiveness of VGs are also evaluated numerically on SUV and Ahmed body with a drag reduction of 4.2% and 10%, respectively [44]. On the other hand, an experimental and numerical investigation has been carried out on a sedan car using 3 delta type of VGs at different yaw angles [45], where the middle VG was kept stationary and remaining two were changed with their angle using smaller stepper motor as shown in Figure 15. In the research, a maximum reduction of drag and lift coefficient have been found as 4.53% and 2.55%, respectively. ...
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... spoiler is an external structure attached to the rear end of the vehicles to control the flow at downstream that helps to minimize the turbulence behind the vehicle and also append downward pressure which reduces the lift. The influence of spoiler on vehicle aerodynamics has numerically investigated on a Toyota Eco car model as shown in Figure 16, and it is found that by using this spoiler at a speed of 30 m/s, drag and lift, respectively can be reduced by 5% and more than 100% [47]. ...
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... performance of flaps has been investigated with three different free stream velocities of 20 m/s, 30 m/s and 40 m/s, by placing two flaps on the side edges of the rear slant and two flaps on the top of the rear slant, and hence the reduction of drag has been found as much as 17.6% and 15%, respectively for the two arrangements of flaps [48]. A special type of flap called Automatic Moving Deflector (AMD) taking inspiration from birds had been tested experimentally on an Ahmed body as shown in Figure 17, by which the maximum drag reduction is achieved from the pressure recovery by AMD which is 19% [49]. ...
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... bottom of a Sedan and Wagon had been modified which has an angle at the bottom rear that acts like an underbody diffuser [51]. The performance of underbody diffuser has been tested with varying angles shown in Figure 18. Results from this study showed a potential aerodynamic drag reduction of the sedan car approximately 10%, and the wagon car by 2-3 %. ...
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... investigation has been carried out on an Ahmed body with non-smooth dimpled surfaces on its slant back [56]. The geometry of non-smooth surfaces are shown in Figure 19. In order to maximize the drag reduction performance of the dimpled non-smooth surface, an aerodynamic optimization method based on a Kriging Surrogate model was employed to design the dimpled non-smooth surface. ...
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... of drag reduction by active and passive methods are graphically presented in Figure 20 and Figure 21 respectively. Maximum contribution of drag reduction for different control methods is shown in Figure 22. ...
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... the above analysis, it is seen that the drag reduction for active control system could be as much as 20% by using the pulse jet [31,32] and plasma actuator [39] as shown in Figure 20 and 22. On the other hand, for passive control system, the drag could be decreased to 21.2% by using Flaps [50] as shown in Figure 21 and 22. However, for combined flow control technique, the drag could be reduced as much as 30% by using blowing jets with porous layer [57] as shown in Figure 22. ...
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... If the momentum required to influence flow could be generated using this technique, it may offer an attractive solution to the problem of ducting in blowing and pulsed jet system. Mukut and Abedin [29] explains that synthetic jet actuator usually consists of orifice, cavity and piezoelectric actuator or diaphragm where flow moves back and forth through a small opening by the oscillation of diaphragm. The movement of diaphragm will momentarily suck and blow fluid across the orifice causing net mass flux in one phase of operation is zero. ...
... The results proven to be able to reduce more drag on sedan vehicle as shown in Figure 32 and Figure 33. Review by Mukut and Abedin [29] also agrees with this and it is found that active flow control has fairly the same ability as passive flow control as shown in Figure 34 indicating the reason why vehicle on roads nowadays still using passive flow control instead of active one. ...
... Highest contribution of DR for different flow controls[29] ...
Reducing aerodynamic drag in automobiles has been one of the focuses in automotive industry as it will increase vehicles performance and reduce power consumption which subsequently save the environment. Drag is a force that tend to pull the vehicle backwards. Pressure drag is the major contributor to drag of vehicle which caused by lower pressure in the rear area compared to front of vehicle. When vehicle moves forward, the stagnation point occurs in the front part of vehicle. The airflow then goes over the vehicle and separate at the back due to adverse pressure gradient. Thus, flow separation is created in the rear area of vehicle as indicated by the wake. Wake is a low-pressure region that need to be reduced so that the pressure between the front and rear could be reduced to minimize the drag. Flow control is introduced to delay this flow separation and it has been categorized as active and passive. Active flow controls require power input while passive flow controls do not need power input. This review article will explore those studies on flow controls applied in automobiles and investigate their working mechanisms along with research gaps detected. Relative comparison of effectiveness for each flow control is unfeasible as the parameters used differs but this problem can be resolved. Standard parameters need to be used in future researches in order address the discrepancy of results obtained from numerous studies around the globe. A current flow control technique is proposed to be conducted in UTM Aerolab to further investigate this interesting flow field.
... Numerous techniques have been investigated to optimize the vehicle aerodynamic forces, including the vortex generator, underbody diffusers, base cavity, deflector, tail plates, and rear spoilers. Some of these techniques can decrease the vehicle drag and lift forces by around 20% [2,3]. It is reported that these techniques can significantly improve the vehicle longitudinal, vertical, and lateral dynamics and, at the same time, improve the vehicle fuel consumption [4]. ...
... High fuel prices, growing concerns for the environmental effect of exhaust emissions, the depletion of fossil fuels greenhouse gas emissions, coupled with the need for continuous performance improvement for road cars and commercial vehicles, fueled an interest in optimizing fuel consumption. Aerodynamic drag and vehicle weight are recognized as the main sources of fuel consumption [1]. According to conducted research by Sudin et al., [2], the aerodynamic drag of road vehicles by itself contributes up to 50 percent of the fuel consumed in highway speeds. ...
In recent years, the aerodynamic drag became a major interest of automotive industry as it is one of the main components affecting the fuel consumption. To reduce aerodynamic drag force and improve the energetic efficiency, a complete understanding of the flow around ground vehicles is highly required. This study focused on the accuracy of a three different turbulence models in predicting Ahmed body components drag coefficients. Ahmed Body is a simplified model which mimics the bluff bodies in automotive aerodynamics. This study uses ANSYS Fluent to simulate the flow around Ahmed Body. Three different turbulence models (K-epsilon, K-omega SST and SST) were used in the study. The drag coefficient components for the different sections of the model were validated with the experimental published data. The results have shown that the SST model predicted accurately the total drag coefficient but failed to provide good agreement for the components drag coefficients.
... The performance of vortex generators to mitigate shock-induced separation and their studies is ranging from those conducted in the early post-war era to those performed recently is reviewed in detail [2]. In addition to an airfoil flow, the vortex generators are also used in non-airfoil flows including an internal flow [3], reducing vehicle drag [4]. These vortex generators are installed with an angle to a free stream and produce a parasitic penalty that increases flow resistance. ...
The present research has introduced a new type of Plasma Vortex Generator named
as Double-Sided Plasma Vortex Generator (DSPVG) that has dual expose electrodes on both sides. This DSPVG is placed normal to the surface parallel to incoming air and creates vortices on it’s both sides. As conventional VG has an angle with flow direction which introduce device drag, to overcome this, DSPVG is placed with zero angle with flow direction; besides due to the smaller thickness and frontal area with incoming air than VGs, the drag penalty due to its geometry is minimized. Furthermore, as vortices are created on both sides, DSPVG is expected to reduce the number of Plasma Vortex Generator (PVG) with respect to the conventional embedded PVGs or VGs on the flow controlling surface. Hence, it is able to take advantage of height like conventional
VGs and active control systems of PVGs with dual vortices on both sides. The impact of DSPVG on separation control has been investigated experimentally and compared its effectiveness with conventional vane VGs. Three different types of flow measurement techniques have been used to confirm the repeatability and consistency of the experimental results. Numerical investigations have been carried out to evaluate the experimental results. These findings show that the DSPVG is capable to eliminate the separation similarly to the conventional VGs but with higher momentum injection and more effective in minimizing drag penalty in the uncontrolled case as in OFF condition
of DSPVG, there is no alternation of local flow which is generally affected in case of VGs that adds drag penalty.
... The car body design is the most complex and important part in the field of automotive production, where there are number of constraints make it a challenging one such as space, esthetics, appeal, style and aerodynamically refined [3,4]. Therefore, and from the early days, the designers understood the significance of drag coefficient reduction and a lot of studies were carried out in this field [5][6][7]. Various researchers used different numerical approaches using CFD for treating the turbulent flows in aerodynamics problems especially large-eddy simulation [8][9][10], direct numerical simulation [11] along with RANS simulation [12]. Song et al. [13] obtained a 5.6% reduction in CD of the sedan car by modifying the rear body shapes. ...
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%.
... In recent years, significant amount of research in automobile industry has focused on the aerodynamic characterization of ground vehicles for efficiency and safety [1]. Several control mechanisms including vortex generators, spoilers and flow control actuators are generally used to streamline the flow over the vehicle, thereby reducing the drag [2]. Control strategy based on flow physics can lead to effective drag reduction and even increasing vehicular stability. ...
... The first three DMD modes are shown in Fig. 6. We identify the clusters and the transition routes corresponding to these modes by multiplying the columns of the TPM (P) with the absolute value of the eigenvectors ( (1) , (2) , (3) ) corresponding to the three oscillatory components, indicated by P (1) , P (2) , P (3) . By doing so, we are highlighting the transitions in the directions of the eigenvectors corresponding to the three frequencies. ...
... The first three DMD modes are shown in Fig. 6. We identify the clusters and the transition routes corresponding to these modes by multiplying the columns of the TPM (P) with the absolute value of the eigenvectors ( (1) , (2) , (3) ) corresponding to the three oscillatory components, indicated by P (1) , P (2) , P (3) . By doing so, we are highlighting the transitions in the directions of the eigenvectors corresponding to the three frequencies. ...
View Video Presentation: https://doi.org/10.2514/6.2022-2429.vid Cluster-based analysis is performed to study the flowfield data from high-fidelity large eddy simulation of a three-dimensional turbulent flow over a Honda sports utility vehicle (SUV) at Re = 5*10^6. The aerodynamic forces (lift, drag, and lateral force coefficients) exerted on the vehicle are chosen to establish the feature space for clustering. The feature space is discretized using the k-means clustering and the dynamics is presented as a finite Markov chain representing the transition probabilities among these clusters. These clusters are then categorized into three communities corresponding to low, intermediate, and high-drag regimes. Since the flow is turbulent, the Markov Chain transition network is complex due to several inter-community transitions. We relate the modes of the Markov chain with modes from dynamical mode decomposition (DMD) to uncover the frequency related information associated with transitions among different drag regimes. The frequencies of the complex eigenvalues of the Markov chain are shown to be related with the first three DMD modes. The weighted Markov chain based on the eigenvectors can identify the dominant transitions among different communities and the associated frequencies. The dominant transitions among the low-drag regimes are associated with low-frequency modes where the large modal structures are observed further from the rear end of the vehicle, whereas the transitions to high-drag regimes are associated with higher frequency DMD modes. Thus, actuation aimed to delay the formation of large low-pressure structures closer to the rear end of the vehicle may result in drag reduction for the Honda SUV model.
... educed vehicle aerodynamic drag, due to modification of vehicle shape, has been shown to enhance vehicle performance, fuel efficiency, reduction in air pollution, handling and safety, aesthetics, and passenger comfort (Gaylard et al., 2014;Le Good et al., 2011;Howell et al., 2014;Huminic & Huminic, 2017;Mukut & Abedin, 2019;Schuetz, 2016). Indiscriminate vehicle shape modifications occur in developing countries where commercial vehicle operators prop vehicle boots to accommodate more loads. ...
Overspeeding and overloading contribute to road accidents. In developing countries, overloading is often indicated by open boot due to commercial transporters’ motivation to carry an excess load to boost revenue. Therefore, there is a need to provide measures to control or eliminate the practice of overspeeding and overloading. This study aims to conduct a parametric study to determine the effect of vehicle speed and boot opening on the aerodynamics of airflow around a typical minibus, fuel consumption, and CO2 emission, and recommend optimum boot opening. Computational Fluid Dynamics is employed using the FLUENT™ program. Results show the existence of a wavy pattern for drag coefficient, fuel consumption, and CO2 emission concerning boot opening. Furthermore, two boot opening regions exist: and . The first region exhibits low prediction error (maximum of 7.25%) and better fit of regression model to FLUENT™ data. The first region also has lower susceptibility to exhibit handling instability. Therefore, boot opening around is recommended as the optimum boot opening, to ensure minimum fuel consumption and CO2 emissions, improve handling and safety. The developed regression models could inform regulatory bodies’ formulation and implementation of policies to mitigate road accidents. Keywords—Boot Opening, CO2 emission, Fuel Consumption, Pressure drag, Total Drag, Minibus, Viscous Drag
... Different flow control methods were researched and discussed in literature. In some papers two method were used together [10][11][12]. A lot of studies have been conducted not only getting the optimum aerodynamic design but also decrease fuel consumption. ...
... Their attachments are little bit easier than pfc. Main disadvantage of active flow control is that it requires power from engine and application of this method increase fuel consumption of vehicles [21]. 5.03% drag minimization was obtained in another study using the afc-pfc techniques for an air vehicle [22]. ...
... Accurate solutions can tell us what is happening in a flow; a fluid dynamicist (or related physicist) is needed to understand how or why it happens. Some pertinent examples include reducing aerodynamic drag for aircraft, trucks, and cars, which holds enormous implications for savings in fuel [4,5] as well as reduction in emissions [6]. Designing safer vehicles is also an important goal for understanding complex aerodynamic phenomena such as stall and flow separation [7]. ...
... 6 shows that the interaction of the disturbance with the separated shear layer is substantially different when actuating instead at t + a = 2.6, which is near the lift minimum of the baseline limit cycle. ...
... 6 shows the compute absolute error between the full state, i.e. X test , and the POD subspace identified from the training dataset. ...
In unsteady aerodynamics the response to external disturbances can depend significantly on the initial condition, and the extent to which this impacts the ability to model the flowfield can vary. In this work, we look to develop a model that can capture and predict the long-time response to actuation, which we suspect to be sensitive to the instantaneous state. We investigate whether a physical understanding of the short-time response to impulsive actuation can be obtained, with the goal of understanding the observed physical phenomenon present in the immediate response to this type of actuation. We find that the response to impulsive actuation is sensitive to the instantaneous wake, and that the short-time response is directly proportional to the time rate of change of the actuation input. Computational simulations of a stalled NACA 0009 airfoil subject to leading-edge synthetic jet actuation were performed. Full state information, as well as force response measurements, were collected using an immersed boundary method (IBM) numerical code. The numerical simulations performed sought to characterize the response to actuation by varying the actuation parameters, such as the strength, direction, and phase at which the onset of actuation occurs. It was found that the long-time response to actuation can be sensitive to the instantaneous wake state at the onset of actuation. The ability to extract models that describe the complex behavior of the system provides additional insight into the dominant features governing the response of such systems, as well as achieves predictive capabilities of the systems' response. The data-driven models, which are identified using variants of dynamic mode decomposition, can capture both the short- and long-time response of the system to actuation. Predictive models are identified using multiple trajectories of data corresponding to varying the phase of vortex shedding at which the onset of actuation occurs. These models achieve accurate predictions for off-design cases as well. It is also shown that multiple control objectives with the same actuator can be achieved. Classical theory aids in understanding the physics governing unsteady aerodynamic motion and the response to disturbances. Theoretical models are developed using the assumptions from classical unsteady aerodynamic theory, which provide insight into the forms that the data-driven models take. The effect of short-duration momentum injection actuation is modeled through a combination of source/sink, doublet, and vortex elements. Regardless of the precise elements used in the theoretical model, the lift response is composed of a contribution directly proportional to the rate of change of actuation strength, and a contribution that persists after the actuation burst ends that arises due to the enforcement of the Kutta condition. Methodologies that retain the physics inherent to the system by projecting the governing equations of motion onto a well-suited basis are extremely valuable for gaining physical insight and understanding into the dynamics of the flowfield. A new methodology is proposed for extracting spectral content from systems with limited data available using projection-based modeling approaches. There are challenges associated with using modal decomposition-based modeling techniques for systems exhibiting large transient dynamics due to external inputs, which is applicable in this particular instance and for related systems. The methodology presented here shows how the dynamics of this system can be understood through analysis of optimal finite-time horizon transient energy growth, applied to reduced-order models identified using actuation response data with either data-driven or physics-based models. A novel methodology is proposed to guide future experimental actuation design to achieve maximal response by considering an optimal forcing mode, identified from considering the optimal perturbation of the full unactuated system, which maximizes a given output.
