Fluid Mechanics: Fundamentals and Applications
... From Eqs. (2) and (3) where f and L are the friction factor and pipe length respectively, and f is calculated as [29]: ...
... The experimental measurements reveal that the Reynolds number is much greater than 2300. The pressure drop due to elbows can be calculated as [29]. ∆ = 2 2 , …(12) where K is the loss coefficient of the elbow and equal to 0.9. ...
... ∆ = 2 2 , …(12) where K is the loss coefficient of the elbow and equal to 0.9. The power needed for air-flow can be calculated as [29]: ...
Earth-air heat exchangers (EAHE) hold great promise for reducing typical air conditioning systems' energy consumption whilst preserving high indoor comfort. The present analyses a 3D model using COMSOL Multiphysics software for a geothermal heat exchanger to examine the thermal behavior along the piping system. The experimental findings of the real EAHE in Baghdad City during January and June are transferred into the nonisothermal pipe flow interface for modeling temperature, velocity and pressure distributions along the piping system. The temperature variation of subsurface soil and the radial temperature distribution around the pipe are modeled into the heat transfer interface. The magnitude of heat flux is also computed in different times along the pipe. The effects of the continuous operation of EAHE on the output temperature and on the soil temperature around the pipe are also considered. The model's output demonstrates that the air temperature rise in January is 10 °C, whereas the air temperature drop is 14 ℃ in June. The effect of extracted/absorbed heat transfer from/to air in pipes is extended up to 0.7 m in the radial direction of the soil surrounding pipes due to continuous airflow in EAHE.
... Analogous to what has been done in Cedillo et al. (2022), we employ a simple yet non-trivial physical problem-namely, the reconstruction of a steady-state, onedimensional water surface profile in a rectangular channel-to isolate the effects of the physically-aided training. The highly informative content of the analyzed problem comes mainly from the hidden complexity of the underlying physics, associated to the possible occurrence of a hydraulic jump, which is not a solution of the differential equation used to determine the water profile (i.e., specific energy equation) (Cengel and Cimbala, 2013). The simulations encompass a wide range of input variations, testing the efficacy of physical training strategies even in data scarce scenarios. ...
... A comprehensive description of the problem is reported in Frontiers in Complex Systems frontiersin.org 03 Cengel and Cimbala (2013) and briefly recalled in Appendix A for the reader's convenience. ...
... The dataset was generated by solving the specific energy equation, expressed as [Cengel and Cimbala, 2013] ...
The application of Neural Networks to river hydraulics and flood mapping is fledgling, despite the field suffering from data scarcity, a challenge for machine learning techniques. Consequently, many purely data-driven Neural Networks have shown limited capabilities when tasked with predicting new scenarios. In this work, we propose introducing physical information into the training phase in the form of a regularization term. Whereas this idea is formally borrowed from Physics-Informed Neural Networks, the proposed methodology does not necessarily resort to PDEs, making it suitable for scenarios with significant epistemic uncertainties, such as river hydraulics. The method enriches the information content of the dataset and appears highly versatile. It shows improved predictive capabilities for a highly controllable, synthetic hydraulic problem, even when extrapolating beyond the boundaries of the training dataset and in data-scarce scenarios. Therefore, our study lays the groundwork for future employment on real datasets from complex applications.
... Nowadays, there are many studies that focus on setting the air jet according to tree canopy with variable air rate application [14][15][16] . In this way, it is possible to send an airflow of proper magnitude according to the tree canopy [17,18] . However, in order to switch to a variable rate application system, the jet characteristics of the airflow must first be regulated and the airflow must be produced with less energy. ...
... The NVS demonstrated a more uniform jet profile compared to the other fans, attributed to its lower coefficient of variation (CV%). The coefficient of variation CV is expected to be <30% for the threshold of a stable jet, according to [18]. Increasing the air velocity and blade angle for each fan also contributed to making the jet smoother. ...
... These losses can be primarily related to the Bernoulli effect (Equation (1)), which states that as the velocity of a fluid flowing through a pipe increases, there will be a corresponding drop in pressure [12]. This pressure drop in the design is induced by the abrupt contraction in the fluid's pathway (Figure 4), from the inlet diameter "d in " (located at section 1-1) to the outlet diameter "d out " (located at section 2-2) [13]. Directly related to this is the continuity equation (Equation (2)), which must ideally be satisfied from the inlet of liquid nitrogen (LN 2 ) into the atomizer to its outlet [13]. ...
... This pressure drop in the design is induced by the abrupt contraction in the fluid's pathway (Figure 4), from the inlet diameter "d in " (located at section 1-1) to the outlet diameter "d out " (located at section 2-2) [13]. Directly related to this is the continuity equation (Equation (2)), which must ideally be satisfied from the inlet of liquid nitrogen (LN 2 ) into the atomizer to its outlet [13]. This equation relates the diameters d in and d out , the latter being reduced to generate a higher exit velocity (Equation (3)). ...
This article addresses the study of internal flow dynamics within a cryogenic chamber designed for freezing food using liquid nitrogen injection. The chamber features a circular section with strategically placed jet-type atomizers for this purpose. The primary objective is to extend the residence time of the cryogenic fluid within the chamber to ensure uniform and effective freezing of the passing food items. This is achieved by inducing a swirl effect through strategic deceleration of the flow using the atomizers. The meticulous placement of these atomizers at periodic intervals along the internal walls of the cylindrical chamber ensures prolonged recirculation of the internal flow. Internal temperature analysis is crucial to ensure the freezing process. The study is supported by numerical analysis in CFD ANSYS to assess the dynamics of the swirl effect and parameters associated with the nitrogen–air interface, from which we obtain a sophisticated analysis thanks to the design of a hexahedral mesh made in greater detail in ICEM CFD. This approach aims to understand internal flow behavior and its correlation with the complexity of cryogenic system design, utilizing variable nitrogen-injection pressures and strategic atomizer placement as fundamental parameters to optimize system design.
... The pressure drop in a pipe can be obtained from the following formula taking into account the major losses that are caused from the friction forces between the fluid and the pipe walls [8], [9]: ...
... where is the fluid density, the length of the pipe, the diameter of the pipe and is the linear losses coefficient that can be approximated from the following formula [9]: ...
... Therefore, when discussing stream loads in the context of bridge piers, they are primarily referred to as drag forces, which are the forces exerted by flowing fluid in the direction of flow. Considering the principles of fluid mechanics (Cengel and Cimbala 2018), the drag pressure is calculated using eq. 3: ...
... The velocity term in this equation indicates that the drag pressure distribution in depth can potentially follow the variation of velocity in depth. In a depthwise distribution of velocity, the near-bed boundary layer affects the velocity distribution (Cengel and Cimbala 2018). Although a boundary layer exists, the approx-imation of a uniform averaged velocity distribution is still valid. ...
Currently, there is an alarming difference in the estimated actions on piers resulting from flash-floods and tsunamis as prescribed by international structural design codes. Previous studies have explored the interaction between surge waves and piers from a fluid-dynamics perspective, but there is no assessment about the relevance of the methods used in Structural Design to determine the hydrodynamic pressure resultants. To determine the degree of conservatism embedded in design, results from the different approaches are compared against validated numerical simulations. Three-dimensional numerical analyses were conducted using the OpenFOAM platform, employing the Large Eddy Simulation turbulence modeling approach to simulate the dam-break wave impacting the pier. The findings revealed that the maximum force was not necessarily caused by the stream’s first strike and could be sustained over time. The hydrodynamic pressure center consistently occurred at two-thirds of the stream depth, significantly impacting the overturning moments experienced by the pier. Identified inconsistencies between Codes underscore the need for revision of nonconservative approaches in predicting the design forces.
... Kemudian menghitung energi yang digunakan untuk menguapkan air selama proses pengeringan, dengan mengalikan massa berat air yang hilang dengan kalor Laten penguapan air [16], sehingga dapat dihitung dengan menggunakan Persamaan (3). Q = m air x L air (3) ...
Penelitian ini menganalisis distribusi udara dan panas yang terjadi pada pengering surya tipe rumah kaca dan rak susun. Analisis dilakukan dengan metode simulasi menggunakan software Computational Fluid Dynamics (CFD) dan dilanjutkan dengan eksperimen. Simulasi dilakukan pada kedua jenis pengering dengan memvariasikan temperatur udara masuk, kecepatan hisap kipas, posisi serta ukuran inlet dan outlet, suhu yang diambil sebagai variabel pengamatan pada simulasi penelitian ini adalah 30oC dan dengan 3 variasi kecepatan aliran udara pada kedua pengering (1, 3, dan 5 m/s). Hasil dari simulasi ini digunakan sebagai basis untuk melakukan eksperimen pengeringan irisan tomat dan kentang. Alat pengering dibuat dengan ukuran masing-masing 95 x 48 x 68 cm untuk rumah kaca dan 95 x 48 x 48 cm untuk rak susun, dengan ukuran inlet dan outlet sama pada keduanya, yaitu 11,5 x 11,5 cm untuk outlet dan 40 x 6 cm untuk bagian inlet. Berat sampel yang akan diuji dengan menggunakan 2 alat pengering ini masing-masing 1 kg tomat dan kentang. Hasil eksperimen yang telah dilakukan didapatkan data pengeringan dengan menggunakan rak susun lebih unggul sekitar 1,8% - 2,97% dalam hal pengurangan massa, dan 0,01 - 0,23oC untuk suhu, serta 0,46 - 0,61% untuk humidity, dibandingkan dengan pengering rumah kaca.
... One particular area of interest is fluid that flows over inclined surfaces, which is so-called fluid inclined problems. These problems arise in various natural and industrial applications such as the movement of water on sloped terrains, oil transport through pipelines, and the design of spillways and drainage systems [1]. ...
The inclined problem is a problem that describes an open fluid flowing over an angled wall. It has broad applications in science and engineering. In this paper, we study the steady state of the inclined problem in two dimensions. The steady-state solution is depicted by the Euler-Lagrange equation of a given energy functional with a fixed contact angle as the boundary condition. By choosing a suitable maximal point to parameterize the surface of the fluid, we can construct a solution to this Euler-Lagrange equation via a shooting method in terms of the volume of the fluid. The construction works for any contact angle and any arbitrary inclined angle.
... The power required for the pump (Ppump) is calculated using Eq. 21 [53]. ...
In the last century, individual transportation vehicles become much more common and they cause great environmental problems. Renewable and sustainable energy solutions will help reduce these environmental problems. Thus, there is a trend towards electric vehicle from internal combustion engine vehicle. Fuel cell electric vehicles, with their competitive driving range, short refueling time and zero emissions, are considered the most likely solution among the vehicle technologies of the future. Since the fuel cell is late to meet the sudden power requirements, it must be hybridized with a second energy device having high power dynamics. In this study, a mid-size passenger vehicle, having 80 kW fuel cell stack supported by a 1.97 kWh battery pack, is modeled with Matlab. The vehicle is simulated on Worldwide Harmonized Light Vehicle Test Procedure (WLTP) Class 3 driving cycle and fuel consumption and range values are 2.15 L/100 km as gasoline equivalent and 859.2 km, respectively. The average efficiency of the internal permanent magnet synchronous motor providing vehicle propulsion is 93.4% throughout the cycle. The overall efficiency of the vehicle is found to be 56.2%, based on the higher heating value of the consumed hydrogen. The emission value of the vehicle is 75.1 gCO2e/km according to the average hydrogen production emission intensity.
... In this experiment, a significant pressure drop was observed at the valve outlet where a foreign object was inserted, resulting in an internal diameter of 3.0 mm. This was defined as the onset of fault, as pressure reduction in laminar flow due to the decrease in internal diameter was quantitatively analyzed using Equation (1) [40]: ...
Faults in valves that regulate fluid flow and pressure in industrial systems can significantly degrade system performance. In systems where multiple valves are used simultaneously, a single valve fault can reduce overall efficiency. Existing fault diagnosis methods struggle with the complexity of multivariate time-series data and unseen fault scenarios. To overcome these challenges, this study proposes a method based on a one-dimensional convolutional neural network (1D CNN) for diagnosing the location and severity of valve faults in a multi-valve system. An experimental setup was constructed with 17 sensors, including 8 pressure sensors at the inlets and outlets of 4 valves, 4 flow sensors, and 5 pressure sensors along the main pipe. Sensor data were collected to observe the sensor values corresponding to valve behavior, and foreign objects of varying sizes were inserted into the valves to simulate faults of different severities. These data were used to train and evaluate the proposed model. The proposed method achieved robust prediction accuracy (MAE: 0.0306, RMSE: 0.0629) compared to existing networks, performing on both trained and unseen fault severities. It identified the location of the faulty valve and quantified fault severity, demonstrating generalization capabilities.
... concentration of NFs (water-based alumina oxide) increases the fluids' thermal diffusivity, which reduces their heat capacity. Figure 13 illustrates that the Nusselt number changes relative to Reynolds number for various NFs with variable particle concentrations ranging from 0.2, 0.4, 0.6, and 0.8 vol%. By using the Gnielinski correlation, the Nusselt number is computed [34]. As the flow rate rises, the NF's Reynolds number in the FPSC increases correspondingly. ...
The heat transfer enhancement in flat plate solar collector (FPSC) can be greatly achieved by the admittance of nanofluids (NFs). This work proposes an experimental investigation to observe the effects of dispersing Al2O3, ZnO, and Al2O3 + ZnO(1:1) nanoparticles in water + ethylene glycol (EG) a base fluid in a 65:35 ratio at different concentrations (0.2, 0.4, 0.6, and 0.8 vol%) on the enhancement of an FPSC. Mass flow rate has an impact on the FPSC's performance in the range of 0.016 kg s−1, 0.033 kg s−1, and 0.05 kg s−1.To examine the optical and structural character of NPs, energy-dispersive X-ray analysis (EDAX) and scanning electron microscopy (SEM) were used. This study addresses the thermophysical characteristics, heat transfer rate, Nusselt number, pumping power, pressure drop, efficiency, and exergy efficiency of FPSC using those mono and hybrid nanofluids (HNF), in comparison with a base fluid. HNF infuse into reference fluid, and the thermal conductivity increases by 71.15%. This improvement was 55.76% for Al2O3/water + EG and 46.15% for ZnO/water + EG NFs, respectively. The heat augmentation of HNF was 78.4% at a flow rate of 0.05 kg s−1, whereas ZnO and Al2O3 NFs had augmentations of 62.15% and 73.84%, respectively. The collector efficiency raised remarkably to 66.7% for HNF, 59% for Al2O3, and 56.5% for ZnO at a mass rate of 0.05 kg s−1.With a mass rate of 0.05 kg s−1, the HNF's exergy efficiency raised by 24.7%, while the Al2O3 and ZnO NFs showed improvements of 21% and 19.5%, respectively, compared to the reference fluid.
... The Reynolds number (Eq. (8)) is one of the most important dimensionless numbers in fluid dynamics, as it predicts the behavior of a flow by calculating the ratio between the inertial and viscous forces [47]. As the Reynolds number increases, the influence of the viscous force becomes less significant, which makes it way more challenging to hold the fluid's disturbance, resulting in more momentum in the flow. ...
Computational Fluid Dynamics (CFD) simulation of viscoplastic fluid flows is challenging. It is critical to capture the shape of the yield surfaces that limit yielded and unyielded flow regions. These are highly sensitive to numerical schemes, which usually rely on calculating velocity derivatives and require highly refined computational grids and strict convergence criteria. In this work, CFD and Deep Neural Networks (DNN) were coupled to develop a model to predict yield surface morphologies for the flow of Bingham fluids in a square cavity. Our main goal is to predict the behavior of viscoplastic fluids using a Machine Learning (ML) approach based on CFD results. Design of Experiments techniques were employed in defining the base cases, i.e., combinations of Bingham and Reynolds numbers (Bn and Re) to compose the DNN training data. The DNN predicted the viscosity fields in the problem domain given Bn and Re. These results were postprocessed using masks to create binary images. The chosen architecture was an encoder-decoder since the input and output data had different dimensions. The results of the surrogate model were adequate, giving a Mean Squared Error of 0.0015 for the training data and 0.002 for the testing data. The DNN-predicted images were consistent with those generated from CFD, corroborating the proposed technique as an excellent alternative to be implemented in more complex applications. The combination of CFD and ML is a promising alternative for predicting complex fluid behavior in diverse and challenging scenarios with faster and computationally less expensive resources.
... How feasible is gravitydriven flow? Equation 11 describes the temperature-dependent mass flow rate of molten regolith along a conduit with circular cross-section 47 : ...
Establishing a permanent, self-sufficient habitat for humans on planetary bodies is critical for successful space exploration. In-situ resource utilisation (ISRU) of locally available resources offers the possibility of an energy-efficient and cost-effective approach. This paper considers the high-temperature processing of molten lunar regolith under conditions which represent the lunar environment, namely low gravity, low temperature, and negligible atmospheric pressure. The rheological properties of the low-titanium lunar mare regolith simulant JSC-1A are measured using concentric cylinder rheometry and these results are used to explore the influence of viscosity on processing operations involving the flow of molten regolith for fabricating construction components on the Moon surface. These include the delivery of molten regolith within an extrusion-based 3D printing technique and the ingress of molten regolith into porous structures. The energy and power required to establish and maintain sufficiently high temperatures for the regolith to remain in the liquid state are also considered and discussed in the context of lunar construction.
... El espesor de la capa límite (δ 99 ) debe quedar dentro de las capas de resolución. Para flujo laminar, este valor se calcula de la Ecuación (13) (Çengel & Cimbala, 2018). Establecer la distribución de las celdas considerando N y G implica resolver ecuaciones no explícitas, lo que demanda métodos numéricos. ...
La inserción de tubérculos en el borde de ataque de un perfil NACA0018, inspirándose en la anatomía de las aletas dorsales de la ballena jorobada, se realizó mediante la adaptación de un perfil sinusoidal. Para ello, se ajustaron la amplitud y el período con respecto a la cuerda promedio del perfil, como parte de una estrategia pasiva para el control del flujo. Con el fin de estimar el comportamiento aerodinámico de los perfiles modificados, se realizaron simulaciones numéricas. Posteriormente, se comparó su rendimiento para implementarlos en un rotor tripala para un aerogenerador de eje vertical tipo Darrieus tripala recto (también conocido como tipo H o giromill). Los álabes propuestos fueron analizados mediante la dinámica de fluidos computacional (CFD) con un enfoque basado en las ecuaciones de Navier-Stokes promediadas en el esquema de Reynolds (RANS, por sus siglas en inglés). Las gráficas de los coeficientes de arrastre y sustentación en función del ángulo de ataque revelaron que la presencia de los tubérculos influye en el rendimiento de los perfiles, especialmente el coeficiente de arrastre. Al examinar los coeficientes de potencia con el esquema denominado "Tubo Doble de Corriente Múltiple (DMST)", se identificó una variación del coeficiente de potencia en la aeroturbina para los casos analizados para distintos valores del TSR. Se presentó un incremento en la eficiencia entre 5,42% y 9,57% (propuesta destacada), mientras que existió una disminución cercana al 40% (propuesta desfavorable) en comparación con el rotor con álabes sin modificar. En consecuencia, la incorporación de los tubérculos puede ser una estrategia viable para mejorar el desempeño aerodinámico del aerogenerador.
... The contact angle ( ) is defined as the angle between the solid surface and the tangent of the free surface of the liquid at the point of contact. The fluid rise due to capillarity is calculated as a function of the contact angle and surface tension of the liquid [19]. ...
... The wagon was positioned 2.1 W downstream from the start of the no-slip floor region with a ride height of 0.16 W. The side and top walls of the computational domain were treated as symmetry boundary conditions to reduce the cell count by eliminating the need for prism layers along these surfaces. Based on the turbulent boundary layer thickness calculated along a flat plate [47]: ...
This study investigates the flow field around a finite rectangular prism using both experimental and computational methods, with a particular focus on the influence of the turbulence approach adopted, the mesh resolution employed, and different subgrid length scales. Ten turbulence modelling and simulation approaches, including both ‘scale-modelling’ Reynolds-Averaged Navier–Stokes (RANS) models and ‘scale-resolving’ Delayed Detached Eddy Simulation (DDES), were tested across six different mesh resolutions. A case with sharp corners allows the location of the flow separation to be fixed, which facilitates a focus on the separated flow region and, in this instance, the three-dimensional interaction of three such regions. The case, therefore, readily enables an assessment of the ‘grey-area’ issue, whereby some DDES methods demonstrate delayed activation of the scale-resolving model, impacting the size of flow recirculation. Experimental measurements were shown to agree well with reference data for the same geometry, after which particle image velocimetry (PIV) data were gathered to extend the reference dataset. Numerical predictions from the RANS models were generally quite reasonable but did not show improvement with further refinement, as one would expect, whereas DDES clearly demonstrated continuous improvement in predictive accuracy with progressive mesh refinement. The shear-layer-adapted (SLA) subgrid length scale (ΔSLA) displayed consistently superior performance compared to the more widely used length scale based on local cell volume, particularly for moderate mesh resolutions commonly employed in industrial settings with limited resources. In general, front-body separation and reattachment exhibited greater sensitivity to mesh refinement than wake resolution. Finally, in order to correlate the observed DDES mesh requirements with the observations from the converged RANS solutions, an approximation for the Taylor microscale was explored as a potential tool for mesh sizing.
... Flow separation is a widespread unfavorable phenomenon that occurs on wind turbine blades during strong winds. The separation point, i.e., the place where the flow separates from the surface, may depend on various factors, such as the level of free flow fluctuations, surface roughness, or Reynolds number [1,2]. It is difficult to predict unless there are sharp edges or sudden changes in the tested surface. ...
Passive flow control around airfoils, wind turbines, and submarines to enhance their aerodynamic properties is the subject of interest in several studies. Previous research provides different solutions, from basic changes in surface roughness and simple geometries to complex shapes and mechanical solutions. This article presents experimental research using the Particle Image Velocimetry (PIV) method on a NACA 0012 airfoil at a Reynolds number of 66,400. Initially, the airfoil was tested for three different angles of attack: 13°, 15°, 17°, and 19°. These tests revealed that angles of attack above 15° significantly increase boundary layer detachment, as shown in the normalized streamwise velocity fields Ux. In the second stage of the research, a different-shaped microcylinder with a characteristic dimension (d/c) of 0.01 was added to the leading edge of the airfoil at a high angle of attack of 17°. Unlike traditional vortex generators placed at the rear of the airfoil, this configuration aimed to reduce boundary layer detachment. The experiment demonstrated that the microcylinder effectively reduced boundary layer detachment at this angle of attack.
... Step 4: Choose j repeating parameters. In order to choose the repeating variables there are a number of guidelines proposed by (Bansal, 2010;Cengel & Cimbala, 2006;Kundu et al., 2012). These guide lines are never pick the dependent variable. ...
and ORCID ID: https://orcid.org/0009-0009-5472-3582 2. Bahir Dar university, Institution of technology, Faculty of Mechanical and industrial Engineering department Agricultural mechanization Engineering. 3. Abstract Fuel consumption in agricultural machinery is the main factor in selecting machinery. During tractor operation, there are different factors that affect fuel consumption in tillage equipment operation. These include the level of power used, working speed, cutting width, soil strength, moisture content, working depth, rolling resistance, and dynamic load on the wheel. This paper reviews the application of dimensional analysis in traction studies and applies dimensional analysis to develop a general equation for fuel consumption for traction. A fuel consumption equation using dimensional analysis with the Buckingham pi theorem developed for traction by considering tyre diameter, tyre width, cone index, wheel dynamic load, rolling resistance, slip, bulk density, and forward speed of the tractor. The developed fuel consumption model equation (= 2 * (, 2 2 , CI 2 , 2 2) *. where, FC is fuel conception ,d is the tire diameter, w, is the tire width, CI is the cone index, W is the wheel dynamic load, R is the rolling resistance, slip, is the soil bulk density, S is the slope and v is the forward speed of the tractor. The developed fuel consumption model considers as the basic fuel consumption affecting parameters and it needs further study and experiments to validate the model.
... To analyze SFA's performance and enhance dynamic controllability, fluidstructure interaction [36] and fluid mechanics [37] should be examined, as fluid ...
Modern industrial and medical applications require soft actuators with practical actuation methods, capable of precision control and high-speed performance. Within the realm of medical robotics, precision and speed imply less complications and reduced operational times. Soft fluidic actuators (SFAs) are promising candidates to replace the current rigid endoscopes due to their mechanical compliance, which offers safer human-robot interaction. However, the most common techniques used to operate SFAs, pneumatics, and hydraulics present limitations that affect their performance. To reduce manufacturing complexity, enhance response time, improve control precision, and augment the usability of SFAs, we propose a pneudraulic actuationsystem that, for the first time, combines a pneumatic and hydraulic circuit in series. To examine this proposal, a comparative assessment of the proposed actuation technique with the common techniques was carried out, in terms of bending performance and generation of audible noise level during functioning. The analysis provides insights into the performance of various fluidic actuation methods for SFAs, highlighting significant effects related to fluid-structure interactions and the presence of trapped air. Thereafter, a comparative assessment of different fluidic circuits is performed, illustrating how tubing length, inner and outer diameter, as well as the amount of different fluidic medium impact the dynamic behavior of the system, amplifying the importance of fluid mechanics for design optimization. Furthermore, we propose a model-based control strategy that solely focuses on fluid dynamics, utilizing the hydraulic-electric analogy and the resistor-inductor-capacitor circuit theory. Our PID controller improved actuation speed by 52.63% and reduced audible noise by 17.17%.
... The key element of energy storage is the storage material. The storage medium applied in the sensible heat storage system is rock, water, concrete, brick, engine oil, ethanol [11][12][13][14]. On the other hand, in latent heat transfer storage system heat is ...
A thermocline is a thin transition layer between hot and cold fluid mixture which is generated by thermal difference of the two fluid layers. A thermocline-based thermal energy storage (TES) tank is one of the most important systems for storing thermal energy for concentrating solar power (CSP) plants. The tank usually consists of different types of rocks as filler materials and molten salts as heat transfer media. Hot and cold fluids are stored in the same tank and the fluids are separated because of their thermal stratification. Thus, a temperature gradient is created between the hot and cold fluid zone, which results in a thermocline. In recent era, burning of fossil fuels make us concerned about its harmful effect on environment and long-term impact on climate change. Solar energy, for its abundance in the form of renewable energy becomes attractive source to generate electricity. Researchers paid their attention to find different thermophysical properties of heat transfer fluids (HTF) like alkali fluorides and molten salts as well as thermophysical properties of phase change materials (PCM). High maximum operational temperature, high heat capacity, high thermal conductivity, good sustainability, and low vapor pressure are the desired properties of HTF. Specific heat, latent heat, and the combination of both are the different forms of stored energy in the thermal energy storage (TES) tank. In the present work, the goal is to analyze thermal performance of TES tank and latent heat thermal energy storage (LHTES) tank numerically for single layered and multi-layered phase change materials (MLPCMs). Molten FLiNaK salt, a eutectic mixture of 46.5% LiF, 11.5% NaF and 42% KF was used as heat transfer media for this scheme. Inorganic salts as well as their mixtures were used as phase change materials. A 2D model of thermocline TES tank was developed which was considered as an isotropic porous medium filled with distinct solid spherical particles. A numerical model was built that describes the way of travelling heat through the thermocline TES tank. Continuity and Momentum equations in porous medium was used for this system to get the flow pattern. The heat transfer module of this numerical model is developed by a special form of energy equation called Dispersion-Concentric (D-C) equation. To solve the problem, the given system was subdivided into smaller, simpler parts. This was achieved by a particular space discretization in the space dimensions, which was implemented by the construction of a mesh of the object. The Finite Element Method (FEM) formulation of a boundary value problem was used to solve these equations. For time dependent equations an implicit method, Backward differentiation formula (BDF) was used. The work was done both for charging and discharging cycles of the heat transfer fluid through the TES tank. The predicted results were compared with the numerical results from the published literature to validate the mathematical model and the numerical scheme. Moreover, two-dimensional graphical representation of velocity, pressure, isothermal contour, streamline etc. were shown and the relation between temperature with time and space were presented. As the research work has been conducted for both single layer and multiple layers TES tank, a comparative study among the different configurations has also been represented. Temperature change with time and space, heat flux in fluids, heat flux in solids are some important key points of comparison in this work. Effect of different phase change materials on temperature were demonstrated. In the charging cycle, PCM F2 has the highest the interstitial heat transfer coefficient (IHTC) and the value is 412.3 W/ (m2. K) however, in the discharging cycle the value is 324.07 W/ (m2. K) for PCM F2. PCM F2 has also the highest value of total enthalpy difference in the charging cycle which is 1676 kJ/kg but in the discharging cycle, PCM F1 has the highest value of total enthalpy difference and the value is 1727 kJ/kg. However, this work helps to uncover a new horizon for storing thermal energy which govern us to harness more energy from sunlight by using concentrated solar collector.
... According to the Bernoulli energy conservation equation [33], when incompressible ideal fluid flow remains steady under the action of gravity, the total sum of the potential, pressure potential, and kinetic energies of the entire flow field are constant on the basis of the energy conservation law. The energy conservation equation of gas flow in the screw vacuum pump is ...
Rotor structure has a great influence on the gas backflow in a screw vacuum pump. The characteristics of the gas main flow along the spiral groove of the screw rotor and the gas reverse flow along the tooth-shaped, tooth side, radial, and circumferential clearances are investigated. A new mathematical model of the pumping flow and backflow involved in a flow balance model is proposed to investigate the actions of the shearing force and pressure difference force. The calculated backflow is verified by comparing the experimental measured results. The relationships of the structural parameters of the screw rotor are established. The effects of the rotor parameters, such as pitch, diameter, and compression ratio, on backflow are revealed. The results show that the rotor diameter and compression ratio remain constant and that the influence of pitch on the backflow is slightly weak, with backflow variations of less than 3%, whereas the pitch, rotor length, and compression ratio are constant and the rotor addendum diameter is directly proportional to the backflow. The addendum diameter of rotor #4 is the largest, and its backflow is about 1.5 times larger than that of rotor #1. When the rotor radial sizes and the pitch of the suction end are constant, the compression ratio is inversely proportional to the backflow in the low-pressure region and proportional to the backflow in the high-pressure regions. Therefore, for a vacuum pump operating in low-pressure areas, the use of the compression ratio of 2.2 or higher is favorable for the reduction in backflow.
... Since the flow through the nozzle is considered turbulent, the compressible flow field is represented by the k- standard model. As stated by Cengel and Cimbala [43], one of the most popular turbulence models, the k-ɛ model, offers sufficient accuracy, economy, and durability for various flow conditions. The Ansys Fluent software provides the k-ɛ turbulence model used in this investigation. ...
The primary purpose of this research is to investigate the effectiveness of rib as a passive control to control the flow development around the circular duct at different levels of expansion using Computational Fluid Dynamics (CFD). The nozzle pressure ratio (NPR), rib size, and rib orientation were considered in this research. The L/D ratio is from 3 to 5; the simulated NPRs were 1.5, 2, 3, 4, and 5. The rib was designed with a quarter circular shape to see the method's effectiveness. The focus was on the duct's base pressure and wall pressure. The results show that the rib size and orientation strongly influenced the base pressure. The base pressure for the model with rib keeps increasing while the base pressure for the model with plain duct shows opposite results as the NPR increases. The base wall's pressure was not affected by nozzle pressure ratio only. Still, other characteristics, such as rib size and orientation, are significant in manipulating the result. However, the rib does not adversely impact the flow in the duct.
... The current study has attempted to find reasons for the intensification of vortex strength due to drain port taper. From the continuity equation, the time to drain out the tank with rotation (t d ) can be obtained and the same is provided in equation 3 [47]. In equation 3, t d is found from experiments and time averaged loss coefficient incurred during draining (ε) is then calculated. ...
... where y H is the dimensional height of the first prism, while y + µ u τ ρ is the height of the wall adjacent cell centroid. The boundary layer thickness is then estimated as a function of the Reynolds number, following [27]. ...
In this article, we present a software tool developed in Python, named T-WorkFlow. It has been devised to meet some of the design needs of Tatuus Racing S.p.a., a leading company in the design and production of racing cars for the FIA Formula 3 Regional and Formula 4 categories. The software leverages the open-source tools OpenFOAM and FreeCAD to fully automate the fluid dynamics simulation process within car radiators. The goal of T-WorkFlow is to provide designers with precise and easily interpretable results that facilitate the identification of the geometry, ensuring optimal flow distribution in the radiator channels. T-WorkFlow requires the radiator’s geometry files in .stp and .stl formats, along with additional user inputs provided through a graphical interface. For mesh generation, the software leverages the OpenFOAM tools blockMesh and snappyHexMesh. To ensure uniform mesh quality across different configurations, and thus, comparable numerical results, various pre-processing operations on the specific geometry files are needed. After generating the mesh, T-WorkFlow automatically defines a control surface for each radiator channel to monitor the volumetric flow rate distribution. This is achieved by combining the OpenFOAM command topoSet with specific geometric information directly obtained from the radiator’s CAD through FreeCAD. During the simulation, the software provides various outputs that automate the main post-processing operations, enabling quick and easy identification of the configuration that ensures the desired performance.
... Thus, if there were no friction, the pressure drop would be zero. Since ΔP depends on friction, ΔP for all types of flow in all types of pipes can be represented as follows [11]. ...
Compact heat exchanger is commonly used in car radiators which is normally small with low flowrate. To produce a large surface area, thin plates or corrugated fins are attached closely separating the two fluids. Compact heat exchanger is normally used in applications where weight and volume are the significant factors for the enhancement of heat transfer. This paper reviews the research related to the characteristics, advantages and findings on various type of compact heat exchanger. It is found that the geometric parameters such as fin shape, tube shape, fin pitch, tube pitch, tube arrangement, tube angle and vortex generators affect the heat transfer performance in general. The air inlet angle of 45° and common flow upstream gives the optimum heat enhancement in most studies while the most suitable air flow is between 1.8 – 3.8 m/s.
... The total lift generated by the airfoil shape blades depends on how much opposite force would be developed due to one-half of the rotor moving in the opposite direction. 25,26 Experiment and results ...
Numerous sites for watermills exist in the world with shallow heads and are possible for power generation either mechanical or electrical. The prime mover required for the energy generation from such sites is in the developing phase with efficient, minimum components, and low cost as a modular unit. The Oryon Watermill (OWM) is one of them developed by Deepwater Energy applicable to water current directly. The working of OWM is used differently on the head drop of the canal with fixed and rotating blades using the NACA 6516 series of airfoil shapes as the novelty of this research. The research covers the CFD simulations with ANSYS Fluent 19.0 of two runners, fabrication, and conduction of tests on-site with a head drop of 1.2 m. The major variable was the water flow rate for both runners with the design discharge of 0.09 m³/s. The analysis of results showed the runner with rotating lamellas performed with 9% and 40% higher efficiency from the simulation and experiment respectively compared to the fixed type. The efficiency achieved from the research is at a low range indicating the availability of large space for future study on performance improvement.
... Moreover, speaking in terms of fluid dynamics, hydrodynamic pressure is generally more homogeneously distributed inside cylindrically shaped channels. At the same time, square and rectangular structures tend to accumulate pressure near the vertices, prompting breaking and leaking at lower flow rates than in cylindrical channels [38]. By comparing both geometries, square channels showed a higher printability (100% against 83%) as compared to cylindrical channels with the smallest diameter at 600 µm. ...
The use of photopolymer-based additive manufacturing (PAM) for the fabrication of microfluidics has recently increased as techniques like Stereolithography (SLA) are employed for the creation of channels by either the printing of a positive mold for casting, or of a monolithic object with embedded hollow structures. The latter is more advantageous; however, no standard metric is available to predict the printability of the embedded hollow structures as a function of their geometry. To address this gap, we selected a lab-on-disc design to confirm that the VAT photopolymerization of embedded hollow structures primarily fails because of channel clogging or collapse due to resin dragging. We introduce the concept of the lowest printable (channel) characteristic length (LPCL) as a threshold geometrical metric at which a minimum of ~ 80% of the hollow structures are successfully printed without collapse or blockage. At this threshold, only the printing failures that are not inherently related to the internal hollow structures remain. The clogging by resin dragging from the VAT is evidenced by the orientation-dependent printability and accuracy, where a 90° angle from the printing platform is ideal for both rectangular and cylindrical channels (LPCL ~ 600 µm). The resin-dependent LPCL increased from 600 to 900–1000 µm as the orientation of the channels decreased towards 0°. Concomitantly, the printing accuracy decreased (95% to 50–80%) linearly with the printing orientation. The LPCL was higher for cylindrical channels than for rectangular. This work contributes to the optimization of PAM settings for the direct fabrication of embedded negative structures inside monolithic objects.
Graphical abstract
Non-Newtonian droplets are used across various applications, including pharmaceuticals, food processing, drug delivery and material science. However, predicting droplet formation using such complex fluids is challenging due to the intricate...
In questo capitolo vengono analizzati alcuni aspetti fondamentali dei fluidi in quiete. Si studia la pressione idrostatica insieme ad alcune sue importanti proprietà. Infine, si analizza la spinta di Archimede alla quale è soggetto, non solo un corpo solido immerso in un fluido, ma anche una massa di fluido con densità diversa da quella ambiente.
In questo capitolo viene discusso il problema generale dei flussi ad alti numeri di Reynolds. Si inizia col considerare lo strato limite, la sua struttura nel caso sia laminare sia turbolento e la sua separazione dal corpo solido. Viene poi trattata la transizione di un flusso interno da potenziale a viscoso. Si analizza inoltre l’irrotazionalità in fluidi perfetti sulla base del classico teorema di Kelvin. Infine, vengono derivati flussi esterni potenziali di interesse aerodinamico e navale.
In questo capitolo vengono introdotti i concetti fondamentali relativi allo stato di moto turbolento in un fluido. Sono descritte le peculiari caratteristiche della turbolenza e viene analizzato il numero adimensionale di Reynolds, che regola la transizione da uno stato di moto laminare ad uno turbolento. Viene inoltre introdotto il concetto di viscosità turbolenta, di fondamentale importanza nelle applicazioni meteo-oceanografiche.
In questo capitolo vengono derivate le equazioni che sono alla base della fluidodinamica in sistemi di riferimento inerziali. Per quanto attiene le forze di superficie, nell’equazione cosiddetta di Eulero compaiono solo gli effetti della pressione, mentre in quella cosiddetta di Navier-Stokes sono considerati anche gli effetti della viscosità molecolare. L’utilizzo di queste equazioni permette di derivare il teorema di Bernoulli, la dinamica di vorticità e vari bilanci energetici.
In fluidodinamica esistono due tipi di forze: le forze di volume e quelle di superficie. Le prime hanno un perfetto corrispettivo nella dinamica Newtoniana del punto materiale mentre le seconde sono specifiche del fluido in quanto sistema continuo. In questo capitolo vengono analizzate le due categorie di forze.
In questo capitolo verranno trattati i principali aspetti cinematici concernenti la fluidodinamica. L’accelerazione di un elemento di fluido, la sua rotazione, la necessità della conservazione della massa sono tutti aspetti di carattere geometrico che esulano dalle forze agenti sul fluido, e che quindi meritano una trattazione a sé stante.
In questo capitolo viene discusso il problema generale dei flussi a bassi numeri di Reynolds. Viene inoltre considerato un interessante esempio di rilevanza meteo-oceanografica.
Besides optimization of pipe network, the HVAC water systems also exhibit significant hysteresis and nonlinear characteristics when undergoing optimized control, which is of important reference significance for improving the decoupling optimization effect of the system. The hysteresis feature refers to the time-delay response characteristics exhibited by the parameters when propagating in the pipeline network, while the nonlinear feature refers to the spatial coupling characteristics of interactions between devices. This chapter will conduct a model study on the hysteresis and nonlinear characteristics of HVAC water systems, constructing the time-delay response characteristics of parameters in the pipeline network and the nonlinear characteristics among various devices. The chapter will first analyze the dynamic response characteristics of water temperature and flow in the HVAC water system pipeline network, exploring the time-delay characteristics of the quality–quantity parameters in the control process. Secondly, it will analyze the influence scale of constitutive parameters on the parameter time-delay response characteristics, verifying the applicability of the time-delay characteristics model in systems of different volumes and structures. Finally, by considering the coupling characteristics among operating parameters of various devices in the system, the chapter will conduct a model study on the spatial characteristics of the system, clarifying the spatial coupling relationships among various devices and control loops. The characteristic model of the HVAC water system established in this chapter will lay the theoretical foundation for subsequent chapters’ research on global optimization methods.
The aim of the present study was to investigate the influence of channel bed geometry (i.e., width B, slope S, bottom length L, and height H of upstream and downstream apron sections) on the discharge capacity and resultant electricity generation of a tidal range power plant. The CFD results showed that the apron width and height significantly affected the discharge capability of sluice passage, while the effects of apron slope and bottom length can be negligible. The mean discharge coefficients for = 1, 3 and 5 (where is the sluice passage width) were 0.77, 0.71 and 0.66, respectively, while 0.79, 0.77 and 0.69 for H/ = 0, 0.25 and 0.5, respectively, indicating significant decreases in the discharge capability with increasing and H/. From the results of 0-D modelling in the case study of the Taedong Bay barrage, the DPR Korea, it is shown that the reduction in the discharge capability of sluice passage resulted in the decrease in the electricity production. The annual power output for the Taedong barrage decreased significantly from 476.6 to 457.9 GWh with increasing H/, showing the largest reduction of about 4.1% for the condition of H/ = 0.5. It can be concluded that the present results will help engineers and scientists to propose an optimal shape for apron section to enhance the discharge capability of sluice passage (and the resultant power output) of tidal range power plants.
In this paper, the dynamic behavior of a twin-tube automotive hydraulic damper is studied. A front axle car damper is subjected to experiments in both phases compression and rebound. Accurate CFD simulations are developed to improve the understanding of the performance of the damper by exploring its hydraulic behaviors in transient response. Dynamic meshing is applied to simulate the fluid flow in terms of velocity and pressure distribution in damper chambers. The deflections of base and piston valve membranes respectively in compression and rebound are determined through an iterative method considering the fluid-structure coupling. Numerical results are in good correlation with those issued from experiments. The presented CFD model is a numerical tool if applied can minimize the number of experiments in the step of design and testing of twin-tube dampers.
Additive manufacturing, particularly 3D printing, has garnered significant attention recently due to its flexibility, precision, and sustainability. Fused Deposition Modeling (FDM)-based 3D printers are among the most popular in the field due to their low cost, practical usage, and print quality. However, one of the major disadvantages of these 3D printers is low print quality or print resolution. The major factor affecting print quality is the nozzle design, including nozzle geometry. Thus, many works in the literature have focused on enhancing 3D printing quality, especially on the nozzle design, which has a substantial impact on printing performance. In this study, the effects of nozzle geometry in three aspects were investigated with a computational fluid dynamics (CFD) perspective: the die angle, and the outlet’s size and shape. The CFD results show that the die angle primarily affects the shear stresses developed in the nozzle, the outlet’s size predominantly impacts velocity and pressure difference, and the outlet’s shape affects shear stress, velocity, and pressure difference to a lesser extent compared to the die angle and size.
This study focuses on applying machine learning (ML) techniques to fluid mechanics problems. Various ML techniques were used to create a series of case studies, where their accuracy and computational costs were compared, and behavior patterns in different problem types were analyzed. The goal is to evaluate the effectiveness and efficiency of ML techniques in fluid mechanics and to contribute to the field by comparing them with traditional methods. Case studies were also conducted using Computational Fluid Dynamics (CFD), and the results were compared with those from ML techniques in terms of accuracy and computational cost. For Case 1, after optimizing relevant parameters, the Artificial Neural Network (ANN), Random Forest (RF), and Support Vector Machine (SVM) models all achieved an R² value above 0.9. However, in Case 2, only the ANN method surpassed this threshold, likely due to the limited data available. In Case 3, all models except for Linear Regression (LR) demonstrated predictive abilities above the 0.9 threshold after parameter optimization. The LR method was found to have low applicability to fluid mechanics problems, while SVM and ANN methods proved to be particularly effective tools after grid search optimization.
Developing new configurations of flanged diffuser-augmented wind turbines is of great importance to reduce the drag force and enhance the output power as much as possible. Thus, six different designs of diffusers categorized into three groups with and without inlet nozzles are presented and investigated in this study. The three groups include a conical part with a flat flange, a conical part with a semicircular flange, and a conical part with a flange of a quarter of a circular flange at the diffusers’ outlets. To assess the performance of these six configurations, a comprehensive 2D axisymmetric model is developed using Reynolds-averaged Navier–Stokes equations coupled with the shear-stress transport k-ω turbulence model. The equations are integrated over the domain using ANSYS FLUENT 2020 R2. The model is numerically simulated and validated using experimental and numerical data. The performance parameters of interest were the power coefficient, the normalized ingested air mass flow rate, the diffuser drag force, and the velocity deficit downstream of the diffuser. Results indicated that combining an inlet nozzle with the diffuser increases the extracted power by 100% and decreases the drag force by 20.7%. In addition, the inlet nozzle depletes the recirculation zone at the diffusers’ inlet. The compact flange combines the advantage of the small-height flat flange and the semicircular flange which enhances the extracted power and reduces the drag force. The current findings confirm that although an inlet nozzle can have significant effects on the output power, there is still much work needed to enhance the performance of flanged diffuser-augmented wind turbine designs.
Introduction
Statics of Fluids
Kinematics of Fluid Flow
Dynamics of Fluid Flow
Momentum Analysis of Flow Systems
Flow in Pipes
Dimensional Analysis and Similarity
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