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.

Vortex system around a step cylinder in a turbulent flow field

“…2 In this regime, the particular Reynolds number 3900 is a benchmark, at which there are many accurate numerical simulations [3][4][5][6] and experimental studies. 7,8 Besides the circular cylinder, due to the extensive applications in marine engineering, e.g., the underwater hull of Single Point Anchor Reservoir (SPAR)-buoy floating offshore wind turbines 9 and the steel lazy wave risers, 10,11 the flow around the step cylinder illustrated in Fig. 1(a) has also attracted attention in recent years.…”

Data on the influence of dynamical impact by mixing on characteristics of turbulent flows in circular pipes

“…Video recording was performed by a monochrome high-speed camera with the frequency of 4000 fps, which is an optimal frequency for subsequent analysis and processing of images at the maximum frame resolution of 1280 × 100 pix. Smoke visualization images were processed using SIV method [1] , [2] , [3] , [4] , [5] , [6] , which provides estimation of the dynamics of velocity vector fields and vorticity fields based on frame-by-frame processing of high-speed video recordings. Vector fields of velocity in this method are estimated from the measured frame-to-frame displacements of turbulent structures visualized by smoke in the light sheet.…”

Modeling the unsteady wake of an impulsively started circular cylinder using refined potential flow theory

“…Because of the regions of the massively separated boundary layer flow, the fully developed Re = 3,900 flow is a classic test case for verification and validation [53,54]. Thus, extensive experimental and computational fluid dynamics studies at Re = 3,900 [53,[55][56][57][58] appear more in the literature than at Re = 56 and Re = 9,500. Therefore, a considerable proportion of the present discussions is skewed towards Re = 3,900.…”