Investigation of unsteady air flow around two-dimensional rectangular cylinders

This paper is aimed at mechanical and civil engineers dealing with practical problems involving flows around structures representing a significant obstacle to the oncoming air (bluff-body structures). It shows the applicability range of relatively simple two-dimensional numerical simulations, explains their limits and offers a set of guidelines, which should help even the non-experts to extract the maximum from the available computer resources. The results of numerical simulations of unsteady flow around three cylinders with rectangular cross-sections are presented. The cylinders are of infinite length and have the cross-sections with width-to-height ratios of 0.2, 1.0 and 5.0. The results obtained by solving Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations are in reasonable agreement with the experimentally measured forces and pressures. The analysis of calculated results shows the physical phenomena responsible for the dramatic drag force reduction, which can be observed when the width-to-height ratio of cylinder is increased.