scholarly journals Development of a Numerical Investigation Framework for Ground Vehicle Platooning

Fluids ◽  
2021 ◽  
Vol 6 (11) ◽  
pp. 404
Author(s):  
Charles Patrick Bounds ◽  
Sudhan Rajasekar ◽  
Mesbah Uddin
Keyword(s):  
Turbulence Model ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Ground Vehicle ◽  
Simulation Methodology ◽  
Vehicle Platooning ◽  
Length Separation ◽  
Dynamics Simulations ◽  
The Impact ◽  
Far Wake

This paper presents a study on the flow dynamics involving vehicle interactions. In order to do so, this study first explores aerodynamic prediction capabilities of popular turbulence models used in computational fluid dynamics simulations involving tandem objects and thus, ultimately presents a framework for CFD simulations of ground vehicle platooning using a realistic vehicle model, DrivAer. Considering the availability of experimental data, the simulation methodology is first developed using a tandem arrangement of surface-mounted cubes which requires an understanding on the role of turbulence models and the impacts of the associated turbulence model closure coefficients on the prediction veracity. It was observed that the prediction accuracy of the SST k−ω turbulence model can be significantly improved through the use of a combination of modified values for the closure coefficients. Additionally, the initial validation studies reveal the inability of the Unsteady Reynolds-Averaged Navier-Stokes (URANS) approach to resolve the far wake, and its frailty in simulating tandem body interactions. The Improved Delayed Detached Eddy Simulations (IDDES) approach can resolve the wakes with a reasonable accuracy. The validated simulation methodology is then applied to the fastback DrivAer model at different longitudinal spacing. The results show that, as the longitudinal spacing is reduced, the trailing car’s drag is increased while the leading car’s drag is decreased which supports prior explanations of vortex impingement as the reason for drag changes. Additionally, unlike the case of platooning involving Ahmed bodies, the trailing model drag does not return to an isolated state value at a two car-length separation. However, the impact of the resolution of the far wake of a detailed DrivAer model, and its implication on the CFD characterization of vehicle interaction aerodynamics need further investigations.

scholarly journals Impact of Underlying RANS Turbulence Models in Zonal Detached Eddy Simulation: Application to a Compressor Rotor

2020 ◽  
Vol 5 (3) ◽  
pp. 22
Author(s):  
Julien Marty ◽  
Cédric Uribe
Keyword(s):  
Turbulence Model ◽  
Turbulence Models ◽  
Adverse Pressure Gradient ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Compressor Rotor ◽  
Rans Turbulence Models ◽  
Unsteady Rans ◽  
The Impact

The present study focuses on the impact of the underlying RANS turbulence model in the Zonal Detached Eddy Simulation (ZDES) method when used for secondary flow prediction. This is carried out in light of three issues commonly investigated for hybrid RANS/LES methods (detection and protection of attached boundary layer, emergence, and growth of resolved turbulent fluctuations and accurate prediction of separation front due to progressive adverse pressure gradient). The studied configuration is the first rotor of a high pressure compressor. Three different turbulence modelings (Spalart and Allmaras model (SA), Menter model with (SST) and without (BSL) shear stress correction) are assessed as ZDES underlying turbulence model and also as turbulence model of unsteady RANS simulations. Whatever the underlying turbulence model, the ZDES behaves well with respect to the first two issues as the boundary layers appear effectively shielded and the RANS-to-LES switch is close downstream of trailing edges and separation fronts leading to a quick LES treatment of wakes and shear layers. Both tip leakage and corner flows are strongly influenced by the Navier–Stokes resolution approach (unsteady RANS vs. ZDES) but the underlying turbulence modelling (SA vs. SST vs. BSL) impacts mainly the junction flow near the hub for both approaches. ZDES underlying turbulence model choice appear essential since it leads to quite different corner flow separation topologies and so to inversion of the downstream stagnation pressure radial gradient.

Numerical Study of the Wave Impact on a Square Column Using Large Eddy Simulation

2007 ◽  
Author(s):  
H. T. C. Pedro ◽  
K.-W. Leung ◽  
M. H. Kobayashi ◽  
H. R. Riggs
Keyword(s):  
Numerical Study ◽  
Turbulence Models ◽  
Simple Algorithm ◽  
Navier Stokes ◽  
Wave Impact ◽  
Eddy Simulation ◽  
Subgrid Model ◽  
Large Eddy ◽  
Volume Approximation ◽  
The Impact

This work concerns the numerical investigation of the impact of a wave on a square column. The wave is generated by a dam break in a wave tank. Two turbulence models were used: Large Eddy Simulations (LES) and Unsteady Reynolds Averaged Navier-Stokes (URANS). The numerical simulations were carried out using a finite volume approximation and the SIMPLE algorithm for the solution of the governing equations. Turbulence was modeled with the standard Smagorinsky-Lilly subgrid-model for the LES and the standard κ-ε model for the URANS. The results are validated against experimental data for the wave impact on a square column facing the flow. The results, especially for LES, show very good agreement between the predictions and experimental results. The overall accuracy of the LES, as expected, is superior to the URANS. However, if computational resources are limited, URANS can still provide satisfactory results for structural design.

scholarly journals Comparison of Computational Fluid Dynamics Simulations and Experiments for Stratified Air-Water Flows in Pipes

2018 ◽  
Vol 141 (5) ◽  
Author(s):  
Gabriele Chinello ◽  
Anis Awal Ayati ◽  
Don McGlinchey ◽  
Gijsbert Ooms ◽  
Ruud Henkes
Keyword(s):  
Turbulence Model ◽  
Oil And Gas ◽  
Oil And Gas Industry ◽  
Experimental Results ◽  
Navier Stokes ◽  
Current Form ◽  
Interface Waves ◽  
Sst Turbulence Model ◽  
Gas Liquid Flow ◽  
Dynamics Simulations

Stratified gas–liquid flow is a flow regime typically encountered in multiphase pipelines. The understanding and modeling of this regime is of engineering importance especially for the oil and gas industry. In this work, simulations have been conducted for stratified air–water flow in pipes. We solved the Reynolds-averaged Navier–Stokes (RANS) equations with the volume of fluid (VOF) method. The aim of this work was to evaluate the performance of the k–ω shear stress transport (SST) turbulence model with and without damping of the turbulence at the gas–liquid interface. Simulation results were compared with some of the latest experimental results found in the literature. A comparison between the simulated velocity and kinetic energy profiles and the experimental results obtained with the particle image velocimetry (PIV) technique was conducted. The characteristics of the interfacial waves were also extracted and compared with the experiments. It is shown that a proper damping of the turbulence close to the interface is needed to obtain agreement with the experimental pressure drop and liquid hold-up. In its current form, however, RANS with the k–ω turbulence model is still not able to give an accurate prediction of the velocity profiles and of the interface waves.

The Impact of Viscous Effects on the Aerodynamic Damping of Vibrating Transonic Compressor Blades—A Numerical Study

2000 ◽  
Vol 123 (2) ◽  
pp. 409-417 ◽  
Author(s):  
Bjo¨rn Gru¨ber ◽  
Volker Carstens
Keyword(s):  
Boundary Layer ◽  
Turbulence Model ◽  
Navier Stokes ◽  
Implicit Time ◽  
Compressor Cascade ◽  
Viscous Effects ◽  
Aerodynamic Forces ◽  
Aerodynamic Damping ◽  
Transonic Compressor ◽  
The Impact

A parametric study which investigates the influence of viscous effects on the damping behavior of vibrating compressor cascades is presented here. To demonstrate the dependence of unsteady aerodynamic forces on the flow viscosity, a computational study was performed for a transonic compressor cascade of which the blades underwent tuned pitching oscillations while the flow conditions extended from fully subsonic to highly transonic flow. Additionally, the reduced frequency and Reynolds number were varied. In order to check the linear behavior of the aerodynamic forces, all calculations were carried out for three different oscillation amplitudes. Comparisons with inviscid Euler results helped identify the influence of viscous effects. The computations were performed with a Navier-Stokes code, the basic features of which are the use of an AUSM upwind scheme, an implicit time integration, and the implementation of the Baldwin-Lomax turbulence model. In order to demonstrate the possibility of this code to correctly predict the unsteady behavior of strong shock-boundary layer interactions, the experiment of Yamamoto and Tanida on a self-induced shock oscillation due to shock-boundary layer interaction was calculated. A significant improvement in the prediction of the shock amplitude was achieved by a slight modification of the Baldwin Lomax turbulence model. An important result of the presented compressor cascade investigations is that viscous effects may cause a significant change in the aerodynamic damping. This behavior is demonstrated by two cases in which an Euler calculation predicts a damped oscillation whereas a Navier-Stokes computation leads to an excited vibration. It was found that the reason for these contrary results are shock-boundary-layer interactions which dramatically change the aerodynamic damping.

scholarly journals Prediction of Airfoil Stall Based on a Modified k−v2¯−ω Turbulence Model

Mathematics ◽  
2022 ◽  
Vol 10 (2) ◽  
pp. 272
Author(s):  
Chenyu Wu ◽  
Haoran Li ◽  
Yufei Zhang ◽  
Haixin Chen
Keyword(s):  
Experimental Data ◽  
Shear Layer ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Trailing Edge ◽  
Naca0012 Airfoil ◽  
Separated Shear Layer ◽  
Non Equilibrium

The accuracy of an airfoil stall prediction heavily depends on the computation of the separated shear layer. Capturing the strong non-equilibrium turbulence in the shear layer is crucial for the accuracy of a stall prediction. In this paper, different Reynolds-averaged Navier–Stokes turbulence models are adopted and compared for airfoil stall prediction. The results show that the separated shear layer fixed k−v2¯−ω (abbreviated as SPF k−v2¯−ω) turbulence model captures the non-equilibrium turbulence in the separated shear layer well and gives satisfactory predictions of both thin-airfoil stall and trailing-edge stall. At small Reynolds numbers (Re~105), the relative error between the predicted CL,max of NACA64A010 by the SPF k−v2¯−ω model and the experimental data is less than 3.5%. At high Reynolds numbers (Re~106), the CL,max of NACA64A010 and NACA64A006 predicted by the SPF k−v2¯−ω model also has an error of less than 5.5% relative to the experimental data. The stall of the NACA0012 airfoil, which features trailing-edge stall, is also computed by the SPF k−v2¯−ω model. The SPF k−v2¯−ω model is also applied to a NACA0012 airfoil, which features trailing-edge stall and an error of CL relative to the experiment at CL>1.0 is smaller than 3.5%. The SPF k−v2¯−ω model shows higher accuracy than other turbulence models.

Development of a Numerical Based Correlation for Performance Losses due to Surface Roughness in Axial Turbines

2014 ◽  
Vol 30 (6) ◽  
pp. 631-642 ◽  
Author(s):  
S. A. Moshizi ◽  
M. H. Nakhaei ◽  
M. J. Kermani ◽  
A. Madadi
Keyword(s):  
Turbulence Model ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Streamline Curvature ◽  
Sst Turbulence Model ◽  
Stator Blade ◽  
Dimensional Models ◽  
Three Dimensional Models ◽  
Axial Turbines

AbstractIn the present work, a recently developed in-house 2D CFD code is used to study the effect of gas turbine stator blade roughness on various performance parameters of a two-dimensional blade cascade. The 2D CFD model is based on a high resolution flux difference splitting scheme of Roe (1981). The Reynolds Averaged Navier-Stokes (RANS) equations are closed using the zero-equation turbulence model of Baldwin-Lomax (1978) and two-equation Shear Stress Transport (SST) turbulence model. For the smooth blade, results are compared with experimental data to validate the model. Finally, a correlation between roughness Reynolds number and loss coefficient for both turbulence models is presented and tested for three other roughness heights. The results of 2D turbine blade cascades can be used for one-dimensional models such as mean line analysis or quasi-three-dimensional models e.g. streamline curvature method.

External Air Flow Over a Pickup Truck: CFD Modeling and Investigation

2016 ◽  
Author(s):  
Scott Kruepke ◽  
Subha Kumpaty
Keyword(s):  
Drag Coefficient ◽  
Air Flow ◽  
Turbulence Models ◽  
Cfd Modeling ◽  
Navier Stokes ◽  
Flow Solver ◽  
Segregated Flow ◽  
Physics Modeling ◽  
The Impact ◽  
Open Position

Pickup trucks offer operators the advantage of towing payload capacity, but at higher operating costs in terms of fuel usage. Some of the increased fuel usage can be attributed to the shape of the truck, which is not aerodynamically advantageous, especially when compared to the other vehicles. This analysis reviews the air flow patterns around a truck during highway travel and uses computational fluid dynamics (CFD) modeling to analyze the best method to predict drag coefficient for the truck. This paper investigates the various mesh features available and the physics models that can be used to approximate the fluid flow, determining the significance of each numerical method. The results indicated that a polyhedral mesh with an incompressible fluid assumption, solved using a segregated flow solver and Reynolds Averaged Navier Stokes k-ε equations provided a suitable balance between accuracy and computational investment when compared to other turbulence models or physics modeling solvers. Further, the analysis investigated the impact on drag of driving the truck with the bed tailgate in the raised, closed position versus driving with the bed tailgate lowered in the open position. The findings actually show that the truck drag coefficient is reduced by about 3% when the truck is operated with the tailgate in the lowered, open position.

scholarly journals THREE-DIMENSIONAL COMPUTATIONAL PREDICTION OF VORTEX SEPARATION PHENOMENON INSIDE THE RANQUE-HILSCH VORTEX TUBE

Aviation ◽  
2016 ◽  
Vol 20 (1) ◽  
pp. 21-31 ◽  
Author(s):  
Seyed Ehsan RAFIEE ◽  
Mohammad Bagher Mohammad SADEGHIAZAD
Keyword(s):  
Turbulence Model ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Computational Prediction ◽  
Separation Process ◽  
Counter Flow ◽  
Vortex Separation ◽  
The Impact ◽  
Air Separator

The air separators are used to provide safe, clean and appropriate air to the helicopter’s engine. In this operational study, the separation process inside a Ranque-Hilsch air separator cleaning system has been investigated to analyze the impact of choosing the appropriate turbulence model for predicting the separation process inside the air separator. This research is directed towards presenting a computational fluid dynamic explanation performed on a counter-flow air separator using air at different magnitudes of air flow fraction and applying different turbulence models. In a numerical investigation of counter-flow air separator, air has been chosen and its vortex separation phe- nomenon has been analyzed as a function of flow fraction. Furthermore, a numerical analysis to compare the outputs of a seven equation RSM turbulence model applied for the study of vortex separation of a counter-flow air separator with some two-equation turbulence methods, namely, k-ε and k-ω model as well as LES has been presented. All of the turbulence numerical methods are seen to present and predict the same flow pattern inside an air separator, but, with various details. The results show that among the tested methods the RSM creates the most accurate separation pattern. The numerical results are validated by some available experimental data with good agreement.

scholarly journals On turbulence models and lidar measurements for wind turbine control

2021 ◽  
Vol 6 (6) ◽  
pp. 1491-1500
Author(s):  
Liang Dong ◽  
Wai Hou Lio ◽  
Eric Simley
Keyword(s):  
Wind Turbine ◽  
Turbulence Model ◽  
Spatial Coherence ◽  
Turbulence Models ◽  
Lidar Measurement ◽  
Wind Turbine Control ◽  
Comprehensive Information ◽  
The Difference ◽  
Turbine Design ◽  
The Impact

Abstract. To provide comprehensive information that will assist in making decisions regarding the adoption of lidar-assisted control (LAC) in wind turbine design, this paper investigates the impact of different turbulence models on the coherence between the rotor-effective wind speed and lidar measurement. First, the differences between the Kaimal and Mann models are discussed, including the power spectrum and spatial coherence. Next, two types of lidar systems are examined to analyze the lidar measurement coherence based on commercially available lidar scan patterns. Finally, numerical simulations have been performed to compare the lidar measurement coherence for different rotor sizes. This work confirms the association between the measurement coherence and the turbulence model. The results indicate that the lidar measurement coherence with the Mann turbulence model is lower than that with the Kaimal turbulence model. In other words, the potential value creation of LAC based on simulations during the wind turbine design phase, evaluated using the Kaimal turbulence model, will be diminished if the Mann turbulence model is used instead. In particular, the difference in coherence is more significant for larger rotors. As a result, this paper suggests that the impacts of different turbulence models should be considered uncertainties while evaluating the benefits of LAC.

scholarly journals Selecting a k-ε turbulence model for investigating n-decane combustion in a diesel engine combustion chamber

2019 ◽  
Vol 7 (2) ◽  
pp. 80-87
Author(s):  
Andrii Avramenko
Keyword(s):  
Numerical Simulation ◽  
Diesel Engine ◽  
Combustion Chamber ◽  
Turbulent Flows ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Toxic Substances ◽  
Engine Combustion ◽  
Experimental Findings ◽  
The Impact

The results of a comparative numerical simulation of combustion and formation of toxic substances in a diesel engine combustion chamber are given. Experimental findings were used to identify the mathematical models. The impact of the standard, RNG and realizable k-ε turbulence models on the accuracy of numerical simulation of combustion and the formation of toxic substances was studied. The realizable k-ε turbulence model was shown to provide a closer agreement of computational and experimental data during simulation of the diesel engine process when turbulent flows are described.

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