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

Abstract

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.

Zonal Detached-Eddy Simulation of tip-leakage flow sensitivity for a compressor rotor

“…This is particularly advantageous when boundary-layer separations occur, since the method has been designed to switch to LES from the separation point, in order to deal with the limitations of RANS regarding separated flows. Although extended to other turbulence models [15], the ZDES formulation used for the present study is the original one and most mature, validated by Riéra on the first rotor of CREATE, associated to the Spalart-Allmaras model (SA model). The second mode of ZDES is used to ensure the RANS treatment of the attached boundary layers, where it is generally welladapted.…”

Aerodynamic simulation of a high-pressure compressor stage using the lattice Boltzmann method

“…Providing that the software and its associated methodology are accurately validated, high-fidelity methods are thus expected to help engineers to improve aerodynamic designs of turbomachines, leading to fuel and emissions reductions of future aero-engines. Several high-fidelity methods have been developed, that can be sorted into two categories, according to the wall treatment: either the flow is resolved up to the wall, as performed in direct numerical simulation and in wall-resolved large-eddy simulation (Dupuy et al , 2020; Priebe et al , 2020; Scillitoe et al , 2017), or a model is used to predict the flow close to the wall, as in wall-modeled large eddy simulation (Odier et al , 2021; Perez-Arroyo et al , 2021) and in the different approaches based on the detached eddy simulation (DES) (Liu et al , 2019; Marty and Uribe, 2020), for which a RANS model is used close to the wall. The first category allows reaching precisely wall bounded flows on a limited domain such as a small amount of blades.…”

The Impact of Various Modeling Decisions on Flow Field Predictions in a Centrifugal Compressor

“…Computational models of compressor cascades have been used to investigate how different turbulence models predict corner separation flows and turbulence anisotropy [8,9]. In a study simulating a rotor in a high-pressure compressor, it was shown that the choice of turbulence model significantly influences the prediction of corner separation [10]. A simulation of the flow through an impeller at 80% speed was performed to compare the performance of the experimental stage with the performance predicted by Spalart-Allmaras, SST, and RS turbulence models.…”