Three Dimensional Turbulent Vortex Shedding From a Surface Mounted Square Cylinder: Predictions With Large Eddy Simulations and URANS

Abstract

The paper reports on the prediction of the turbulent flow field around a threedimensional, surface mounted, squaresectioned cylinder at Reynolds numbers in the range 104–105. The effects of turbulence are accounted for in two different ways: by performing largeeddy simulations (LES) with a Smagorinsky model for the subgridscale motions and by solving the unsteady form of the Reynoldsaveraged Navier–Stokes equations (URANS) together with a turbulence model to determine the resulting Reynolds stresses. The turbulence model used is a twoequation, eddyviscosity closure that incorporates a term designed to account for the interactions between the organized meanflow periodicity and the random turbulent motions. Comparisons with experimental data show that the two approaches yield results that are generally comparable and in good accord with the experimental data. The main conclusion of this work is that the URANS approach, which is considerably less demanding in terms of computer resources than LES, can reliably be used for the prediction of unsteady separated flows provided that the effects of organized meanflow unsteadiness on the turbulence are properly accounted for in the turbulence model.