Budget analysis of turbulent kinetic energy in corner separation: RANS vs les

Abstract

The aim of the study is to compare the LES of corner separation, considered as a reference, in the LMFA-NACA65 linear compressor cascade to RANS simulations using Wilcox two-equation models (k - ω). The LES was carried-out by Gao et al. [1] using the Shear-improved Smagorinsky model (SISM), and has been validated by comparison with the experimental data obtained by Ma et al. [2]. Two steady RANS simulations are carried out using k - ω models: Wilcox 1988 model and Wilcox 1988 model with quadratic constitutive relation. First, the analysis will consider the total pressure losses on a two-dimensional section downstream of the cascade. The Reynolds stresses and the turbulent kinetic energy budget are analysed within the separation region, on a two-dimensional section at the trailing edge of the blade. The RANS simulations mostly overestimate the total pressure losses and the size of the corner separation, compared to the LES and the experiment. The RANS simulations also overestimate the level of the Reynolds stresses and the terms of the turbulent kinetic energy budget, compared to the LES. The quadratic constitutive relation yields some modifications, but not significant enough to have results comparable to LES.