SIV measurements of flow structure in the near wake of a circular cylinder at Re = 3900

Abstract

Turbulent characteristics of a near wake behind a circular cylinder in a cross flow at Re = 3900 were considered. This regime of flow past cylinders has been widely discussed in the literature; however, the published experimental data and numerical simulation results experience some controversy. Furthermore, there is a shortage of reliable experimental data, e.g. the available descriptions of experimental setups and conditions are not enough for testing of numerical methods. The present paper fills this gap to a large extent. Experiments were carried out using a relatively new smoke image velocimetry (SIV) technique, which provides time-resolved measurements of instantaneous two-dimensional velocity vector fields in complex turbulent flows with high spatial resolution of the order of Kolmogorov scale. Distributions of flow statistics over different cross sections of the cylinder wake were obtained. Comparative analysis of SIV measurements and previously published experimental and DNS data was performed. The sources of differences in distributions of turbulence statistics were analysed. Key regularities in evolution of velocity profiles in the cylinder wake were revealed. Some features were discovered in the distributions of transverse velocity component and fluctuating flow parameters that had not been previously captured by other measurement methods. Physical mechanisms and their origins are described.