Investigation of flow characteristics around a freely falling rigid sphere in a bounded fluid domain employing the shear stress transport k−ω improved delayed detached eddy simulation model

2022 ◽  
Vol 34 (1) ◽  
pp. 015108
Author(s):  
Deepak K. Pandey ◽  
Juhun Song ◽  
Hee-Chang Lim
Keyword(s):  
Shear Stress ◽  
Simulation Model ◽  
Flow Characteristics ◽  
Rigid Sphere ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Shear Stress Transport ◽  
Delayed Detached Eddy Simulation

scholarly journals Adaptability of Turbulence Models for Pantograph Aerodynamic Noise Simulation

2019 ◽  
Vol 2019 ◽  
pp. 1-20 ◽  
Author(s):  
Xiao-ming Tan ◽  
Peng-peng Xie ◽  
Zhi-gang Yang ◽  
Jian-yong Gao
Keyword(s):  
Shear Stress ◽  
Wind Tunnel ◽  
High Speed ◽  
Aerodynamic Noise ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Shear Stress Transport ◽  
Delayed Detached Eddy Simulation ◽  
Relative Errors ◽  
Les Model

This study was targeted at CX-PG-type Faiveley pantograph of high-speed train and cylinders and analysed the fluctuating flow field around these objects by using the large eddy simulation (LES) model, the scale adaptive simulation (SAS) model, the improved delayed detached eddy simulation with shear-stress transport-kω (IDDES sst-kω) model, the delayed detached eddy simulation with shear-stress transport-kω (DDES sst-kω) model, and the delayed detached eddy simulation with realizable-kε (DDES R-kε) model. The space distributions of velocity, vorticity, and vortex structures were compared to investigate their performances on simulating fluctuating flow fields and computing aeroacoustic sources through Fourier transformation based on the surface fluctuating pressures. Furthermore, the far-field radiated noise was calculated based on the Ffowcs Williams–Hawkings equation. Based on the computation precision of the five models, a feasible turbulent model was selected for simulating aerodynamic noise. The relative errors to the results from wind-tunnel experiments of the sound pressure level (SPL) were obtained as 0.7%, 1.6%, 7.8%, 3.8%, and 12.1%, respectively, and the peak Strouhal numbers were obtained as 2.0%, 8.5%, 5.5%, 11.5%, and 51.0% for cylinder simulation. Moreover, the relative errors of SAS, IDDES sst-kω, DDES sst-kω, and DDES R-kε models to the result from LES of SPL were respectively obtained as 2.3%, 4.5%, 5.6%, and 10.8% for pantograph. Thus, it is conclusive that none of the aforementioned models are comparable with the LES model with respect to the precision in the aeroacoustic simulation. However, SAS, IDDES sst-kω, and DDES sst-kω are practically competent with the LES model considering the numerical simulations with respect to the engineering computation precision. The numerical computation model was verified using the wind-tunnel test results.

Numerical Implementation of Detached-Eddy Simulation on a Passenger Vehicle and Some Experimental Correlation

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
L. Sterken ◽  
S. Sebben ◽  
L. Löfdahl
Keyword(s):  
Flow Characteristics ◽  
Industrial Applications ◽  
Operating Conditions ◽  
Wake Flow ◽  
Computational Time ◽  
Detached Eddy Simulation ◽  
Passenger Vehicle ◽  
Ansys Fluent ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation

This study presents an implementation of delayed detached-eddy simulation (DDES) on a full-scale passenger vehicle for three configurations with the use of commercial software harpoon (mesher) and ansys fluent (solver). The methodology aims to simulate the flow accurately around complex geometries at relevantly high Re numbers for use in industrial applications, within an acceptable computational time. Geometric differences between the three configurations ensure significant drag changes that have a strong effect on the wake formation behind the vehicle. Therefore, this paper focuses on the analysis of the base wake region. At first, the paper evaluates the performance of the DDES, where it verifies the different operating conditions of the flow around the vehicle with respect to the DDES definition. In a second step, the numerical results are correlated with force measurements and time-averaged flow field investigations, conducted in the Volvo Cars aerodynamic wind tunnel (WT). The comparison confirms a good agreement between the experiments and the simulations. The resolved flow scales obtained by DDES give a further insight into differences in the wake flow characteristics between the configurations related to their contribution to drag.

COMPUTATIONAL AERODYNAMICS OF THE C-130 PREDICTING AIRFLOW EFFECT ON AIRDROP

2013 ◽  
Vol 10 (05) ◽  
pp. 1350025 ◽  
Author(s):  
EDDIE YIN KWEE NG ◽  
SAMUEL KHENG HONG PANG ◽  
WEN SHAN CHIU
Keyword(s):  
Shear Stress ◽  
Numerical Simulations ◽  
Vortex Core ◽  
Detached Eddy Simulation ◽  
Safe Distance ◽  
Aircraft Model ◽  
Eddy Simulation ◽  
Computational Aerodynamics ◽  
Delayed Detached Eddy Simulation ◽  
Large Vortex

This paper presents a delayed detached-eddy simulation-shear stress transport (DDES-SST) analysis of the airflow in the opened cargo hatch region of the C-130H. Numerical simulations are performed on a full-scaled axisymmetric aircraft model with the standard airdrop method settings at a 5° angle of attack. Results show a large vortex core forming at the mouth of the cargo bay and diminishing in strength and vorticity with distance from the cargo ramp. An approximate safe distance for deployment of extraction parachutes is also measured with the help of streamline plots.

Comparisons of Shear Stress Transport and Detached Eddy Simulations of the Flow Around Trains

2018 ◽  
Vol 140 (11) ◽  
Author(s):  
Tian Li ◽  
Hassan Hemida ◽  
Jiye Zhang ◽  
Mohammad Rashidi ◽  
Dominic Flynn
Keyword(s):  
Experimental Data ◽  
Shear Stress ◽  
Flow Field ◽  
Surface Pressure ◽  
Experimental Uncertainty ◽  
Detached Eddy Simulation ◽  
Aerodynamic Forces ◽  
Force Coefficients ◽  
Eddy Simulation ◽  
Shear Stress Transport

Shear stress transport (SST) k–ω model and detached eddy simulation (DES) have been widely applied in crosswind stability simulations for trains in the literature. In the previous research, the influence of the SST and DES approaches on the flow field around trains, which affects the surface pressure and consequently the aerodynamic forces of the train, was not properly investigated in terms of their influence flow field. The SST and improved delayed detached eddy simulation (IDDES) turbulence models have been tested in this study for their ability to predict the flow field around, surface pressure, and aerodynamic forces on a 1/25th scale Class 390 train subjected to crosswinds. Numerical simulation results were validated with experimental data. Results show that both SST and IDDES predict similar trends in the mean flow field around the train. However, there were some slight differences observed in the size of vortices, the position of separation points, and consequently, the separation and attachment lines. The SST results compared more closely to the experimental data than IDDES for pressure coefficient on the leeward surface and roof at certain loops. Slight differences were observed in force coefficients for SST and DES. The side force coefficients calculated using computational fluid dynamics (CFD) sit within the experimental uncertainty, whereas the lift force coefficients deviated greatly due to the omission of some underbody geometrical features. Both SST and IDDES approaches used the linear-upwind stabilized transport (LUST) scheme and were able to predict accurately the time-averaged surface pressure within the margin of the experimental uncertainty.

Detached-Eddy Simulation With Compressibility Corrections Applied to a Supersonic Axisymmetric Base Flow

2002 ◽  
Vol 124 (4) ◽  
pp. 911-923 ◽  
Author(s):  
James R. Forsythe ◽  
Klaus A. Hoffmann ◽  
Russell M. Cummings ◽  
Kyle D. Squires
Keyword(s):  
Shear Stress ◽  
Large Eddy Simulation ◽  
Base Flow ◽  
Navier Stokes ◽  
Future Application ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Shear Stress Transport ◽  
Large Eddy ◽  
Reynolds Averaged Navier Stokes

Detached-eddy simulation is applied to an axisymmetric base flow at supersonic conditions. Detached-eddy simulation is a hybrid approach to modeling turbulence that combines the best features of the Reynolds-averaged Navier-Stokes and large-eddy simulation approaches. In the Reynolds-averaged mode, the model is currently based on either the Spalart-Allmaras turbulence model or Menter’s shear stress transport model; in the large-eddy simulation mode, it is based on the Smagorinski subgrid scale model. The intended application of detached-eddy simulation is the treatment of massively separated, high-Reynolds number flows over complex configurations (entire aircraft, automobiles, etc.). Because of the intented future application of the methods to complex configurations, Cobalt, an unstructured grid Navier-Stokes solver, is used. The current work incorporates compressible shear layer corrections in both the Spalart-Allmaras and shear stress transport-based detached-eddy simulation models. The effect of these corrections on both detached-eddy simulation and Reynolds-averaged Navier-Stokes models is examined, and comparisons are made to the experiments of Herrin and Dutton. Solutions are obtained on several grids—both structured and unstructured—to test the sensitivity of the models and code to grid refinement and grid type. The results show that predictions of base flows using detached-eddy simulation compare very well with available experimental data, including turbulence quantities in the wake of the axisymmetric body.

Study On the Applicability of URANS, LES and Hybrid LES/RANS Models for Prediction of Hydrodynamics of Cyclone Separator

2021 ◽  
Author(s):  
Sai Guruprasad Jakkala ◽  
S Vengadesan
Keyword(s):  
Fluid Flow ◽  
Flow Characteristics ◽  
Mesh Size ◽  
Turbulent Energy ◽  
Computational Time ◽  
Detached Eddy Simulation ◽  
Reynolds Stresses ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation ◽  
Rans Models

Abstract Cyclone separators are an integral part of many industrial processes. A good understanding of the flow features is paramount to efficiently use them. The turbulent fluid flow characteristics are modelled using URANS, LES and hybrid LES/RANS turbulent models. The hybrid LES/RANS approaches, namely DES (Detached Eddy Simulation), DDES (Delayed Detached Eddy Simulation) and IDDES (Improved Delayed Detached Eddy Simulation) based on the k - $\omega$ SST RANS approaches are explored. The study is carried out for three different inlet velocities (v = 8, 16:1, and 32 m=s). The results from hybrid LES/RANS models are shown to be in good agreement with the experimental data available in the literature. Reduction in computational time and mesh size are the two main benefits of using hybrid LES/RANS models over the traditional LES methods. The Reynolds stresses are observed in order to understand the redistribution of turbulent energy in the flow field. The velocity profiles and vorticity quantities are explored to obtain a better understanding of the behaviour of fluid flow in cyclone separators.

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