Assessment of algebraic subgrid scale models for the flow over a triangular cylinder at Re = 45000

Abstract

The turbulent separated flow over an equilateral triangular cylinder at a Reynolds number 45000 (based on the triangle edge) is studied by means of large-eddy simulation (LES). The moderate Reynolds number is chosen in order to replicate available experimental data (Laser Doppler Anemometry measurements at the Volvo test rig). The OpenFoam CFD toolbox is used for the present numerical simulations. Several algebraic subgrid scale (SGS) closures, including the conventional Smagorinsky model (Cs = 0.1 and Cs = 0.053), the model by Vreman (Cs = 0.1) and the dynamic version of the k-equation model are investigated. The spectral analysis of the vortex shedding and the convective instabilities as well as the turbulence kinetic energy dissipation rate is presented. Some aspects of the blockage effects are investigated and compared to experimental data available in the literature. It was shown that blockage affects significantly the mean drag and pressure coefficients of the triangular cylinder. At the same time the mean velocity field is tending to similarity. Overall, all SGS models reproduced most important aspects of the flow physics of the separated bluff-body flow, including integral flow parameters and spectral characteristics with dispersion about 10%, showing a reasonable consistency with the experimental data.