Numerical Simulation of Separation Control in Backward Facing Step Turbulent Flow

2002 ◽  
Author(s):  
Emmanuel Guilmineau ◽  
Patrick Queutey
Keyword(s):  
Experimental Data ◽  
Reynolds Stress ◽  
Transport Model ◽  
Turbulence Models ◽  
Separated Flow ◽  
Separation Control ◽  
Local Perturbation ◽  
Backward Facing Step ◽  
Reynolds Stress Transport Model ◽  
Turbulent Separated Flow

The control of turbulent separated flow over the backward-facing step is numerically investigated with various turbulence models ranging from one equation Spalart & Allmaras (1992), two-equation K-ω closures (Wilcox, 1988; Menter, 1993) to a full Reynolds stress transport model based on the Reynolds stress transport Rij-ω model (Deng & Visonneau, 1999). Results are compared with experimental data of Yoshioka et al. (1999) where the flow control was monitoring with alternating suction/injection at the step height. It is shown that the effect of that local perturbation is better represented using the Rij-ω turbulence model.

Prediction of the Flow Around an Airfoil Using a Reynolds Stress Transport Model

1995 ◽  
Vol 117 (1) ◽  
pp. 50-57 ◽  
Author(s):  
Lars Davidson
Keyword(s):  
Experimental Data ◽  
Reynolds Stress ◽  
Transport Model ◽  
Suction Side ◽  
Equation Model ◽  
Staggered Grid ◽  
Poor Agreement ◽  
Third Order ◽  
Reynolds Stress Transport Model ◽  
Quick Scheme

A second-moment Reynolds Stress Transport Model (RSTM) is used in the present work for computing the flow around a two-dimensional airfoil. An incompressible SIMPLEC code is used, employing a non-staggered grid arrangement. A third-order QUICK scheme is used for the momentum equations, and a second-order, bounded MUSCL scheme is used for the turbulent quantities. As the RSTM is valid only for fully turbulent flow, an eddy viscosity, one-equation model is used near the wall. The two models are matched along a preselected grid line in the fully turbulent region. Detailed comparisons between calculations and experiments are presented for an angle of attack of α = 13.3 deg. The RSTM predictions agree well with the experiments, and approaching stall is predicted for α = 17 deg, which agrees well with experimental data. The results obtained with a two-layer κ – ∈ model show poor agreement with experimental data; the velocity profiles on the suction side of the airfoil show no tendency of separation, and no tendency of stall is predicted.

Computer Simulations of Airflow Field Around a Cube: Comparisons of LES and RANS Models

2010 ◽  
Author(s):  
Behtash Tavakoli ◽  
Goodarz Ahmadi
Keyword(s):  
Experimental Data ◽  
Computational Models ◽  
Transport Model ◽  
Separated Flow ◽  
Realistic Model ◽  
Navier Stokes ◽  
Reynolds Stress Transport Model ◽  
Rans Models ◽  
Airflow Field ◽  
Computationally Intensive

Simulations of flow field around wall mounted square cylinders have been used extensively for validation of computational models in the literature. In this paper the airflow fields around a square cylinder were simulated using the Reynolds Averaged Navier-Stokes (RANS) models as well as the Large Eddy Simulations (LES). Particular attention was given to the case with Reynolds number of 80,000 for which the experimental data of Hussein and Matinuzzi [1] are available. The nature of the 3D wakes behind the cube as well as the vortices in front and at the back of the cube were investigated. The simulation results were compared with the experimental data and the accuracy of different models were studied. While the LES better captured the features of this separated flow, it is computationally intensive. The Reynolds Stress Transport Model (RSTM) did not properly predict some features of this separated flow, but is comparatively more economical. The accuracy of RSTM for predicting the turbulence features of separated flows was discussed, and its application for the flow around a realistic model of a building was pointed out.

A Comparison of Unsteady RANS Simulations With PIV Data in an Axial Turbomachine

2005 ◽  
Author(s):  
Daniel Brzozowski ◽  
Oguz Uzol ◽  
Yi-Chih Chow ◽  
Joseph Katz ◽  
Charles Meneveau
Keyword(s):  
Experimental Data ◽  
Transport Model ◽  
Energy Levels ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Piv Measurements ◽  
Flow Solver ◽  
Reynolds Stress Transport Model ◽  
Flow Features ◽  
Rans Simulations

This paper presents a comparison of 2D unsteady Reynolds Averaged Navier-Stokes (RANS) simulations using two standard turbulence models, i.e. RNG k-ε and a Reynolds Stress Transport Model, with experimental data, obtained using two-dimensional Particle Image Velocimetry (PIV) measurements within an entire stage of an axial turbomachine. The computations are performed using the commercial flow solver FLUENT™. A sliding mesh interface between the rotor and stator domains is used. The PIV measurements are performed in a refractive-index-matched facility that provides unobstructed view, and cover the entire 2nd stage of a two-stage axial pump. The inlet velocity and turbulence boundary conditions are provided from the experimental data. Detailed side-by-side comparisons of computed and measured phase-averaged velocity as well as turbulence fields within the entire stage are presented. Quantitative comparisons between the experiments and the computations are also included in terms of line distributions within the rotor-stator gap and the stator wake regions. The results show that, although there is reasonable agreement in general between the experimental results and the computational simulations, some critical flow features are not correctly predicted. The turbulent kinetic energy levels are generally too high in the simulations, with substantial amount of unphysical turbulence generation near the blade leading edges, especially in the case of RNG k-ε model.

Improved Prediction of Turbomachinery Flows Using Near-Wall Reynolds-Stress Model

2001 ◽  
Vol 124 (1) ◽  
pp. 86-99 ◽  
Author(s):  
G. A. Gerolymos ◽  
J. Neubauer ◽  
V. C. Sharma ◽  
I. Vallet
Keyword(s):  
Experimental Data ◽  
Turbulent Flows ◽  
Reynolds Stress ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Stress Model ◽  
Reynolds Stresses ◽  
Mean Flow ◽  
Flow Equations ◽  
Near Wall

In this paper an assessment of the improvement in the prediction of complex turbomachinery flows using a new near-wall Reynolds-stress model is attempted. The turbulence closure used is a near-wall low-turbulence-Reynolds-number Reynolds-stress model, that is independent of the distance-from-the-wall and of the normal-to-the-wall direction. The model takes into account the Coriolis redistribution effect on the Reynolds-stresses. The five mean flow equations and the seven turbulence model equations are solved using an implicit coupled OΔx3 upwind-biased solver. Results are compared with experimental data for three turbomachinery configurations: the NTUA high subsonic annular cascade, the NASA_37 rotor, and the RWTH 1 1/2 stage turbine. A detailed analysis of the flowfield is given. It is seen that the new model that takes into account the Reynolds-stress anisotropy substantially improves the agreement with experimental data, particularily for flows with large separation, while being only 30 percent more expensive than the k−ε model (thanks to an efficient implicit implementation). It is believed that further work on advanced turbulence models will substantially enhance the predictive capability of complex turbulent flows in turbomachinery.

Sensitization of the SST Turbulence Model to Rotation and Curvature by Applying the Spalart–Shur Correction Term

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Pavel E. Smirnov ◽  
Florian R. Menter
Keyword(s):  
Turbulent Flows ◽  
Turbulence Model ◽  
Transport Model ◽  
Correction Term ◽  
Computational Cost ◽  
Turbulence Models ◽  
Reynolds Stress Transport Model ◽  
Wide Range ◽  
Sst Model ◽  
The One

A rotation-curvature correction suggested earlier by Spalart and Shur (1997, “On the Sensitization of Turbulence Models to Rotation and Curvature,” Aerosp. Sci. Technol., 1(5), pp. 297–302) for the one-equation Spalart–Allmaras turbulence model is adapted to the shear stress transport model. This new version of the model (SST-CC) has been extensively tested on a wide range of both wall-bounded and free shear turbulent flows with system rotation and/or streamline curvature. Predictions of the SST-CC model are compared with available experimental and direct numerical simulations (DNS) data, on the one hand, and with the corresponding results of the original SST model and advanced Reynolds stress transport model (RSM), on the other hand. It is found that in terms of accuracy the proposed model significantly improves the original SST model and is quite competitive with the RSM, whereas its computational cost is significantly less than that of the RSM.

scholarly journals A Second-Order Turbulence Model Based on a Reynolds Stress Approach for Two-Phase Flow—Part I: Adiabatic Cases

2009 ◽  
Vol 2009 ◽  
pp. 1-14 ◽  
Author(s):  
S. Mimouni ◽  
F. Archambeau ◽  
M. Boucker ◽  
J. Laviéville ◽  
C. Morel
Keyword(s):  
Liquid Phase ◽  
Reynolds Stress ◽  
Turbulence Model ◽  
Two Phase Flow ◽  
Turbulence Modeling ◽  
Transport Model ◽  
Phase Flow ◽  
Two Phase ◽  
Model Based ◽  
Reynolds Stress Transport Model

In our work in 2008, we evaluated the aptitude of the code Neptune_CFD to reproduce the incidence of a structure topped by vanes on a boiling layer, within the framework of the Neptune project. The objective was to reproduce the main effects of the spacer grids. The turbulence of the liquid phase was modeled by a first-orderK-εmodel. We show in this paper that this model is unable to describe the turbulence of rotating flows, in accordance with the theory. The objective of this paper is to improve the turbulence modeling of the liquid phase by a second turbulence model based on aRij-εapproach. Results obtained on typical single-phase cases highlight the improvement of the prediction for all computed values. We tested the turbulence modelRij-εimplemented in the code versus typical adiabatic two-phase flow experiments. We check that the simulations with the Reynolds stress transport model (RSTM) give satisfactory results in a simple geometry as compared to aK-εmodel: this point is crucial before calculating rod bundle geometries where theK-εmodel may fail.

INVESTIGATION OF INLET EFFECTS ON BACKWARD-FACING STEP FLOW PREDICTION

2016 ◽  
Vol 40 (3) ◽  
pp. 317-329 ◽  
Author(s):  
Mustafa Kemal Isman
Keyword(s):  
Experimental Data ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Backward Facing Step ◽  
Step Flow ◽  
Uniform Velocity ◽  
Flow Prediction ◽  
Rans Turbulence Models ◽  
Negative Effect ◽  
Inlet Boundary Condition

The turbulent flow over backward-facing step (BFS) is numerically investigated by using FLUENT® code. Both uniform and non-uniform velocity profiles are used as inlet boundary condition. Five different Reynolds averaged Navier–Stokes (RANS) turbulence models are employed. The Std. k–ω model shows the best agreement with the experimental data among the models used under the conditions considered in this study. The results show that using a uniform velocity profile has a negative effect on predictions if the domain is not sufficiently extended upstream from the inlet. To eliminate this effect, the domain should be extended upstream by about 10Dh from the inlet. However, results show that this extension causes absorption effects of inlet parameters such as inlet turbulence intensity.

A New Unsteady-Based Turbulence Model to Predict Shear Layer Rollup and Breakdown

2004 ◽  
Author(s):  
D. Scott Holloway ◽  
James H. Leylek
Keyword(s):  
Shear Layer ◽  
Reynolds Stress ◽  
Turbulence Model ◽  
Turbine Blades ◽  
Turbulence Models ◽  
Separated Flow ◽  
Leading Edge ◽  
Tip Clearance ◽  
Aircraft Carrier ◽  
Flow Through

This paper documents the computational investigation of the unsteady rollup and breakdown of a turbulent separated shear layer. This complex phenomenon plays a key role in many applications, such as separated flow at the leading edge of an airfoil at off-design conditions; flow through the tip clearance of a rotor in a gas turbine; flow over the front of an automobile or aircraft carrier; and flow through turbulated passages that are used to cool turbine blades. Computationally, this problem poses a significant challenge in the use of traditional RANS-based turbulence models for the prediction of unsteady flows. To demonstrate this point, a series of 2-D and 3-D unsteady simulations have been performed using a variety of well-known turbulence models, including the “realizable” k-ε model, a differential Reynolds stress model, and a new model developed by the present authors that contains physics that account for the effects of local unsteadiness on turbulence. All simulations are fully converged and grid independent in the unsteady framework. A proven computational methodology is used that takes care of several important aspects, including high-quality meshes (2.5 million finite volumes for 3-D simulations) and a discretization scheme that will minimize the effects of numerical diffusion. To isolate the shear layer breakdown phenomenon, the well-studied flow over a blunt leading edge (Reynolds number based on plate half-thickness of 26,000) is used for validation. Surprisingly, none of the traditional eddy-viscosity or Reynolds stress models are able to predict an unsteady behavior even with modifications in the near-wall treatment, repeated adaption of the mesh, or by adding small random perturbations to the flow field. The newly developed unsteady-based turbulence model is shown to predict some important features of the shear layer rollup and breakdown.

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