A ROBUST IMPLEMENTATION OF A REYNOLDS STRESS MODEL FOR TURBOMACHINERY APPLICATIONS IN A COUPLED SOLVER ENVIRONMENT

Abstract In the industrial simulation of flow phenomena, turbulence modeling is of prime importance. Due to their low computational cost, Reynolds-averaged methods (RANS) are predominantly used for this purpose. However, eddy viscosity RANS models are often unable to adequately capture important flow physics, specifically when strongly anisotropic turbulence and vortex structures are present. In such cases the more costly 7-equation Reynolds stress models often lead to significantly better results. Unfortunately, these models are not widely used in the industry. The reason for this is not mainly the increased computational cost, but the stability and convergence issues such models usually exhibit. In this paper we present a robust implementation of a Reynolds stress model that is solved in a coupled manner, increasing stability and convergence speed significantly compared to segregated implementations. In addition, the decoupling of the velocity and Reynolds stress fields is addressed for the coupled equation formulation. A special wall function is presented that conserves the anisotropic properties of the model near the walls on coarser meshes. The presented Reynolds stress model is validated on a series of semi-academic test cases and then applied to two industrially relevant situations, namely the tip vortex of a NACA0012 profile and the Aachen Radiver radial compressor case.

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Robust Implicit Multigrid Reynolds-Stress Model Computation of 3-D Turbomachinery Flows

Volume 6: Turbomachinery, Parts A and B ◽

10.1115/gt2006-91324 ◽

2006 ◽

Cited By ~ 4

Author(s):

G. A. Gerolymos ◽

I. Vallet

Keyword(s):

Reynolds Stress ◽

Time Integration ◽

Computational Cost ◽

Turbulence Models ◽

Reynolds Stress Model ◽

Finite Volume Scheme ◽

Stress Model ◽

Mean Flow ◽

Approximate Factorization ◽

Flow Equations

The purpose of this paper is to present a numerical methodology for the computation of complex 3-D turbomachinery flows using advanced multiequation turbulence closures, including full 7-equation Reynolds-stress transport models. A general frame-work describing the turbulence models and possible future improvements is presented. The flow equations are discretized on structured multiblock grids, using an upwind biased (O[Δx3] MUSCL reconstruction) finite-volume scheme. Time-integration uses a local-dual-time-stepping implicit procedure, with internal subiterations. Computational efficiency is achieved by a specific approximate factorization of the implicit subiterations, designed to minimize the computational cost of the turbulence-transport-equations. Convergence is still accelerated using a mean-flow-multigrid full-approximation-scheme method, where multigrid is applied on the mean-flow-variables only. Speed-ups of a factor 3 are obtained using 3 levels of multigrid (fine + 2 coarser grids). Computational examples are presented using several Reynolds-stress model variants (and also a baseline k–ε model), for various turbomachinery configurations, and compared with available experimental measurements.

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Modeling of Cube Array Roughness: RANS, LES, and DNS

10.1115/fedsm2021-65494 ◽

2021 ◽

Author(s):

Samuel Altland ◽

Haosen H. A. Xu ◽

Xiang I. A. Yang ◽

Robert Kunz

Keyword(s):

Reynolds Stress ◽

Significant Degree ◽

Reynolds Stress Model ◽

Stress Model ◽

Mean Velocity ◽

Flow Features ◽

Drag Partition ◽

Flow Phenomena ◽

Rans Models ◽

Packing Densities

Abstract Flow over arrays of cubes is an extensively studied model problem for rough wall turbulent boundary layers. While considerable research has been performed in computationally investigating these topologies using DNS and LES, the ability of sublayer-resolved RANS to predict the bulk flow phenomena of these systems is relatively unexplored, especially at low and high packing densities. Here, RANS simulations are conducted on six different packing densities of cubes in aligned and staggered configurations. The packing densities investigated span from what would classically be defined as isolated, up to those in the d-type roughness regime, filling in the gap in the present literature. Three different sublayer-resolved turbulence closure models were tested for each case; a low Reynolds number k-ε model, the Menter k-ω SST model, and a full Reynolds stress model. Comparisons of the velocity fields, secondary flow features, and drag coefficients are made between the RANS results and existing LES and DNS results. There is a significant degree of variability in the performance of the various RANS models across all comparison metrics. However, the Reynolds stress model demonstrated the best accuracy in terms of the mean velocity profile as well as drag partition across the range of packing densities.

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A Robust Implementation of a Reynolds Stress Model for Turbomachinery Applications in a Coupled Solver Environment

10.1115/1.0003224v ◽

2021 ◽

Author(s):

Ernesto Casartelli ◽

David Roos ◽

Luca Mangani ◽

Francesco Del Citto

Keyword(s):

Reynolds Stress ◽

Reynolds Stress Model ◽

Stress Model ◽

Robust Implementation

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Application of the Reynolds Stress Model to Direct Modeling and Actuator Disk Simulations of a Small-Scale Horizontal-Axis Wind Turbine

Volume 1B, Symposia: Fluid Mechanics (Fundamental Issues and Perspectives; Industrial and Environmental Applications); Multiphase Flow and Systems (Multiscale Methods; Noninvasive Measurements; Numerical Methods; Heat Transfer; Performance); Transport Phenomena (Clean Energy; Mixing; Manufacturing and Materials Processing); Turbulent Flows — Issues and Perspectives; Algorithms and Applications for High Performance CFD Computation; Fluid Power; Fluid Dynamics of Wind Energy; Marine Hydrodynamics ◽

10.1115/fedsm2016-7595 ◽

2016 ◽

Cited By ~ 1

Author(s):

Randall Jackson ◽

Ryoichi S. Amano

Keyword(s):

Wind Turbine ◽

Reynolds Stress ◽

Reynolds Stress Model ◽

Horizontal Axis ◽

Tip Vortex ◽

Small Scale ◽

Stress Model ◽

Closure Model ◽

Horizontal Axis Wind Turbine ◽

Turbulence Closure Model

Computational Fluid Dynamics (CFD) has become a staple in wind energy research and studies cover a broad range of topics including atmospheric wind profiles, airfoil design, wind turbine design, terrain effects, and wake dynamics. One of the most important aspects of applying CFD methods is the selection of a turbulence closure model when solving the Reynolds Averaged Navier-Stokes (RANS) equations. In this research, the Reynolds Stress Model (RSM) was applied to predict the wake turbulence and velocity profiles for a small scale, 3-bladed, horizontal-axis wind turbine (HAWT) using a commercial CFD software, Star CCM+. The wind turbine was modeled directly by discretizing the rotor and also using an actuator disc concept to simulate the rotor. Wind tunnel experiments were performed using hot-wire anemometry to measure the velocity deficit at various downstream locations. High speed images were also captured to examine qualitatively the wake and tip vortex dissipation created from an oil mist. The CFD results show the RSM turbulence closure model to be excellent in predicting the wake velocity and tip vortex structure when compared to experimental results.

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