Low-frequency variations in the wake of a circular cylinder at Re = 3900

Abstract

Flow around cylindrical structures is of relevance for many practical applications. Knowledge of flow-related unsteady loading of such structures is crucial for hydro- and aerodynamic control and design. In order to obtain a deeper knowledge of this kind of flow, a DNS have been performed at ReD = 3900 (ReD = UrefD/v). The instantaneous velocity signals of probes located in the separated shear-layer and in the vortex formation region exhibit the presence of low-frequency variations. The statistical analysis of these signals suggest that low-frequency variations in the vortex formation length, suction base pressure and intermittencies in the shear layer are closely related. It is shown that these variations are the responsible of the large scattering of data obtained in different experimental and numerical results, as well as the U-shape and V-shape stream-wise velocity profiles observed in the very near wake of the cylinder.