High-order Large Eddy Simulations of Confined Rotor-Stator Flows

TL;DR

This study compares two high-order LES methods for accurately simulating turbulent rotor-stator flows at high Reynolds number, demonstrating LES's superiority over RANS in capturing complex unsteady flow structures.

Contribution

It provides a quantitative comparison of the dynamic Smagorinsky model and spectral vanishing viscosity LES techniques for rotor-stator flows at Re=400000.

Findings

Both LES methods accurately predict unsteady flow structures.

Spectral SVV shows slight advantages in accuracy and computational efficiency.

LES outperforms RANS in modeling turbulent and transitional regimes.

Abstract

In many engineering and industrial applications, the investigation of rotating turbulent flow is of great interest. In rotor-stator cavities, the centrifugal and Coriolis forces have a strong influence on the turbulence by producing a secondary flow in the meridian plane composed of two thin boundary layers along the disks separated by a non-viscous geostrophic core. Most numerical simulations have been performed using RANS and URANS modelling, and very few investigations have been performed using LES. This paper reports on quantitative comparisons of two high-order LES methods to predict a turbulent rotor-stator flow at the rotational Reynolds number Re=400000. The classical dynamic Smagorinsky model for the subgrid-scale stress (Germano et al., Phys Fluids A 3(7):1760-1765, 1991) is compared to a spectral vanishing viscosity technique (S\'everac & Serre, J Comp Phys 226(2):1234-1255, 2007). Numerical results include both instantaneous data and postprocessed statistics. The results show that both LES methods are able to accurately describe the unsteady flow structures and to satisfactorily predict mean velocities as well as Reynolds stress tensor components. A slight advantage is given to the spectral SVV approach in terms of accuracy and CPU cost. The strong improvements obtained in the present results with respect to RANS results confirm that LES is the appropriate level of modelling for flows in which fully turbulent and transition regimes are involved.