Investigation of flow structures in a turbulent separating flow using hybrid RANS-LES model

TL;DR

This study evaluates the performance of hybrid RANS-LES models in simulating turbulent separating flows, demonstrating comparable accuracy to LES at coarse grid resolutions and emphasizing the importance of both mean and instantaneous flow analysis.

Contribution

It provides a comparative assessment of hybrid RANS-LES and LES models for turbulent flows, highlighting the effectiveness of hybrid models at coarse resolutions using POD analysis.

Findings

Hybrid RANS-LES achieves similar accuracy to LES at coarse grid resolutions.

Both mean and instantaneous flow fields are effectively captured by hybrid models.

Two-point statistics via POD reveal unsteady flow characteristics.

Abstract

Hybrid Reynolds-averaged Navier Stokes large eddy simulation (RANS LES) methods have become popular for simulation of massively separated flows at high Reynolds numbers due to their reduced computational cost and good accuracy. The current study aims to examine the performance of LES and hybrid RANS-LES model for a given grid resolution. For better assessment and contrast of model performance, both mean and instantaneous flow fields have been investigated. For studying instantaneous flow, proper orthogonal decomposition has been used. Current analysis shows that hybrid RANS-LES is capable of achieving similar accuracy in prediction of both mean and instantaneous flow fields at a very coarse grid as compared to LES. Focusing mostly on the practical applications of computation, most of the attention has been given to the prediction of one-point flow statistics and little consideration has been put to two-point statistics. Here, two-point statistics has been considered using POD to investigate unsteady turbulent flow.