On the Investigation of Flow around the Square Cylinder Based on Different LES Models

2012 ◽  
Vol 594-597 ◽  
pp. 2676-2679
Author(s):  
Zhe Liu
Keyword(s):  
Flow Characteristics ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Square Cylinder ◽  
Rans Model ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Reynolds Averaged Navier Stokes ◽  
Les Model

Although the conventional Reynolds-averaged Navier–Stokes (RANS) model has been widely applied in the industrial and engineering field, it is worthwhile to study whether these models are suitable to investigate the flow filed varying with the time. With the development of turbulence models, the unsteady Reynolds-averaged Navier–Stokes (URANS) model, detached eddy simulation (DES) and large eddy simulation (LES) compensate the disadvantage of RANS model. This paper mainly presents the theory of standard LES model, LES dynamic model and wall-adapting local eddy-viscosity (WALE) LES model. And the square cylinder is selected as the research target to study the flow characteristics around it at Reynolds number 13,000. The influence of different LES models on the flow field around the square cylinder is compared.

Detached-Eddy Simulations and Reynolds-Averaged Navier-Stokes Simulations of Delta Wing Vortical Flowfields

2002 ◽  
Vol 124 (4) ◽  
pp. 924-932 ◽  
Author(s):  
Scott Morton ◽  
James Forsythe ◽  
Anthony Mitchell ◽  
David Hajek
Keyword(s):  
Vortex Breakdown ◽  
Delta Wing ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Fighter Aircraft ◽  
Eddy Simulation ◽  
Reynolds Averaged Navier Stokes ◽  
High Reynolds

An understanding of vortical structures and vortex breakdown is essential for the development of highly maneuverable vehicles and high angle of attack flight. This is primarily due to the physical limits these phenomena impose on aircraft and missiles at extreme flight conditions. Demands for more maneuverable air vehicles have pushed the limits of current CFD methods in the high Reynolds number regime. Simulation methods must be able to accurately describe the unsteady, vortical flowfields associated with fighter aircraft at Reynolds numbers more representative of full-scale vehicles. It is the goal of this paper to demonstrate the ability of detached-eddy Simulation (DES), a hybrid Reynolds-averaged Navier-Stokes (RANS)/large-eddy Simulation (LES) method, to accurately predict vortex breakdown at Reynolds numbers above 1×106. Detailed experiments performed at Onera are used to compare simulations utilizing both RANS and DES turbulence models.

Numerical study of transonic cavity flows using large-eddy and detached-eddy simulation

2007 ◽  
Vol 111 (1117) ◽  
pp. 153-164 ◽  
Author(s):  
P. Nayyar ◽  
G. N. Barakos ◽  
K. J. Badcock
Keyword(s):  
Energy Content ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Complex Flow ◽  
Promising Alternative ◽  
Eddy Simulation ◽  
Massively Separated Flows ◽  
Large Eddy

Numerical analysis of the flow in weapon bays modelled as open rectangular cavities of length-to-depth (L/D) ratio of 5 and width-to-depth (W/D) ratio of 1 with doors-on and doors-off is presented. Flow conditions correspond to Mach and Reynolds numbers (based on cavity length) of 0·85 and 6·783m respectively. Results from unsteady Reynolds-averaged Navier-Stokes (URANS), large-eddy simulation (LES) and detached-eddy simulation (DES) are compared with the simulation methods demonstrating the best prediction of this complex flow. It was found that URANS was not able to predict the change of flow characteristics between the doors-on and doors-off configurations. In addition, the energy content of the cavity flow modes was much better resolved with DES and LES. Further, the DES was found to be quite capable for this problem giving accurate results (within 3dB of) experiments and appears to be a promising alternative to LES for modelling massively separated flows.

Effect of URANS and Hybrid RANS-Large Eddy Simulation Turbulence Models on Unsteady Turbulent Flows Inside a Side Channel Pump

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Yefang Wang ◽  
Fan Zhang ◽  
Shouqi Yuan ◽  
Ke Chen ◽  
Xueyuan Wei ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Turbulence Models ◽  
Swirling Flows ◽  
Navier Stokes ◽  
Side Channel ◽  
Fluid Exchange ◽  
Eddy Simulation ◽  
Internal Fluid ◽  
Large Eddy ◽  
Reynolds Averaged Navier Stokes

Abstract In this work, the unsteady Reynolds-averaged Navier–Stokes (URANS) and three hybrid Reynolds-averaged Navier–Stokes-large eddy simulation (RANS-LES) models are employed to resolve the vortical flows in a typical single-stage side channel pump, to evaluate the suitability of these advanced turbulence models in predicting the pump hydraulic performance and unstable swirling flows. By the comparison of the overall performance, it can be observed that the results obtained by scale-adapted simulation (SAS) are closer to test data than shear stress transport (SST), detached eddy simulation (DES) and filter-based model (FBM). Simultaneously, the distribution of axial velocity on the plane near the interface is used to describe the position and intensity of internal fluid exchange between impeller and side channel. It is obvious that the intensity of mass flow exchange is strong near the inner and outer edges. Then, the vortex core region illustrates that the vortex is easily produced near the interface due to internal fluid exchange. Finally, the evolutions of circumferential in-plane vortical structures are presented to further account for the process of fluid exchange and the main vortex flows. It reveals that the recirculation flow presents a strong instability during 6–7 blade pitches as the fluid enters into the impeller and the flow is stable in downstream 7–8 blade pitches. Besides, the flow turns to be unsteady near outlet affected by the sudden change of fluid direction. This work could provide some suggestions for the choice of appropriate turbulence model in simulating strong swirling flows.

Detached-Eddy Simulation of Flow Around the NREL Phase-VI Blade

2002 ◽  
Author(s):  
J. Johansen ◽  
N. N. So̸rensen ◽  
J. A. Michelsen ◽  
S. Schreck
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Simulation Model ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Reynolds Averaged Navier Stokes ◽  
Nrel Phase Vi

The Detached-Eddy Simulation model implemented in the computational fluid dynamics code, EllipSys3D, is applied on the flow around the NREL Phase-VI wind turbine blade. Results are presented for flow around a parked blade at fixed angle of attack and a blade pitching along the blade axis. Computed blade characteristics are compared with experimental data from the NREL/NASA Ames Phase-VI unsteady experiment. The Detached-Eddy Simulation model is a method for predicting turbulence in computational fluid dynamics computations, which combines a Reynolds Averaged Navier-Stokes method in the boundary layer with a Large Eddy Simulation in the free shear flow. The present study focuses on static and dynamic stall regions highly relevant for stall regulated wind turbines. Computations do predict force coefficients and pressure distributions fairly good and results using Detached-Eddy Simulation show considerably more three-dimensional flow structures compared to conventional two-equation Reynolds Averaged Navier-Stokes turbulence models, but no particular improvements are seen on the global blade characteristics.

scholarly journals Effect of Local Grid Refinement on Performance of Scale-Resolving Models for Simulation of Complex External Flows

Aerospace ◽  
2019 ◽  
Vol 6 (8) ◽  
pp. 86 ◽  
Author(s):  
Amne ElCheikh ◽  
Michel ElKhoury
Keyword(s):  
Computational Cost ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Pollutant Dispersion ◽  
Uniform Grid ◽  
Grid Refinement ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Uniform Grids ◽  
Large Eddy

Numerical simulations are crucial for fast and accurate estimations of the flow characteristics in many engineering applications such as atmospheric boundary layers around buildings, external aerodynamics around vehicles, and pollutant dispersion. In the simulation of flow over urban-like obstacles, it is crucial to accurately resolve the flow characteristics with reasonable computational cost. Therefore, Large Eddy Simulations on non-uniform grids are usually employed. However, an undesirable accumulation of energy at grid-refinement interfaces was observed in previous studies using non-uniform grids. This phenomenon induced oscillations in the spanwise velocity component, mainly on fine-to-coarse grid interfaces. In this study, the two challenging test cases of flow over urban-like cubes and flow over a 3-D circular cylinder were simulated using three different scale-resolving turbulence models. Simulations were performed on uniform coarse and fine grids on one hand, and a non-uniform grid on the other, to assess the effect of mesh density and mesh interfaces on the models’ performance. Overall, the proposed One-Equation Scale-Adaptive Simulation (One-Equation SAS) showed the least deviation from the experimental results in both tested cases and on all grid sizes and types when compared to the Shear Stress Transport-Improved Delayed Detached Eddy Simulation (IDDES) and the Algebraic Wall-Modeled Large Eddy Simulation (WMLES).

scholarly journals Компьютерное моделирование течения в микрофакельных горелочных устройствах с асимметричной подачей топлива

2018 ◽  
Vol 28 (8) ◽  
pp. 117-121
Author(s):  
N. M. Fialko ◽  
V. G. Prokopov ◽  
S. O. Alioshko ◽  
M. Z. Abdulin ◽  
K. V. Rokitko ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Reynolds Averaged Navier Stokes

Выявлены основные закономерности изотермического течения топлива и окислителя в микрофакельном горелочном устройстве с односторонней подачей топлива. Получены данные компьютерного моделирования с использованием подхода DES (Detached Eddy Simulation), представляющего собой комбинацию моделей RANS (Reynolds Averaged Navier-Stokes) и LES (Large Eddy Simulation) в разных областях пространства. Установлены эффекты влияния длины закрылка, расположенного на торцевой поверхности стабилизаторов пламени, на различные характеристики течения. Показано, что наличие закрылков приводит к существенному изменению вихревой структуры в следе за стабилизаторами. Оценено влияние длины закрылков на такие параметры течения, как протяженность зоны обратных токов в закормовой области стабилизаторов пламени, уровень среднеквадратичных пульсаций скорости в данных зонах и пр. Установлено, что с увеличением длины закрылков существенно возрастает протяженность зоны обратных токов за стабилизатором. Выявлено также, что чем короче закрылки, тем больше превышает их длину протяженность зоны обратных токов. Выполнен анализ пространственного распределения пульсаций скорости в рассматриваемом горелочном устройстве при наличии и отсутствии закрылков на торцевых поверхностях стабилизаторов пламени. Показано, что наиболее высокий уровень данных пульсаций наблюдается вблизи границы зоны обратных токов, удаленной от торца стабилизатора. Установлено, что уровень среднеквадратичных пульсаций скорости является наиболее высоким в условиях отсутствия закрылка и снижается при увеличении его длины.

A New Hybrid RANS/LES Modeling Methodology for CFD Applications

2011 ◽  
Author(s):  
Mohammad F. Alam ◽  
D. Keith Walters ◽  
David S. Thompson
Keyword(s):  
Turbulence Models ◽  
Detached Eddy Simulation ◽  
Backward Facing Step ◽  
Mean Velocity ◽  
New Model ◽  
Rans Model ◽  
Eddy Simulation ◽  
Modeling Methodology ◽  
Sst Model ◽  
Les Model

The primary weakness of current hybrid RANS/LES (HRL) models lies in the treatment of the “transition zone,” where the value and the physical interpretation of the eddy viscosity changes from LES to RANS, or vice versa. In order to address this problem, the initial version of a new HRL modeling methodology has been developed that incorporates two separate turbulent stress parameters (one from the LES model and the other from the RANS model). In this paper, the viability of the new model is demonstrated by predictions of the flow over a backward facing step, which is one of the canonical test cases used for the validation of turbulence models. The simulation results of backward facing step flow at ReH = 37,000 provided by Menter’s Shear Stress Transport (SST) model, a new version of Detached Eddy Simulation (DES) i.e. delayed DES model, and the new model are compared with experiments. Mesh sensitivity of the models is also studied employing two different types of mesh, in order to test the wide applicability of the HRL models in various realistic flow simulations. Pressure and skin friction distributions and mean velocity profiles obtained with the new HRL model show improved agreement with the experimental measurements versus DES, and less sensitivity to the mesh details. Turbulent kinetic energy profiles of both the new model and the RANS model show qualitatively good agreement with experiments.

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.

Selection of Suitable Turbulence Models for Numerical Modelling of Hydrocyclones

2011 ◽  
Vol 6 (1) ◽  
Author(s):  
Mohsen Karimi ◽  
Guven Akdogan ◽  
Ali Dehghani ◽  
Steven Bradshaw
Keyword(s):  
Swirling Flow ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Boussinesq Hypothesis ◽  
Large Eddy ◽  
Comprehensive Survey ◽  
Computational Fluid Dynamics Cfd ◽  
Les Model

The capability of Computational Fluid Dynamics (CFD) alternates the interest of researcher from the empirical models into the numerical approaches for studying hydrocyclones. This paper presents a comprehensive survey on the influences of turbulence model options in the 3D simulation of the hydrocyclone flow pattern. The required grid resolution was selected through a grid independency study. Four categories of turbulence models involving models based on the Boussinesq hypothesis, the Reynolds Stress Model (RSM), the Large Eddy Simulation (LES) model, and the Detached Eddy Simulation (DES) model were investigated for prediction of velocity components within the hydrocyclone. The methodology was validated by experimental data. The results confirm that both RSM and LES models are efficient turbulent model choices for the simulation of swirling flow of hydrocyclones.

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