Flow features of three side-by-side rectangular cylinders under the effect of aspect ratios and Reynolds numbers

Abstract

This study focuses on the characteristics of flow past three side-by-side rectangular cylinders under the effect of aspect ratios (AR) and Reynolds numbers (Re) at two different gap ratios ([Formula: see text]) using the lattice Boltzmann method. For this purpose, AR is varied in the range of 0.25–4, the Re values are 100, 140 and 180 and the two different values of [Formula: see text] taken into account are [Formula: see text] and 3. The results are presented in the form of vorticity contours, temporal histories of drag and lift coefficients and power spectrum of lift coefficients. Also, the variation of physical parameters like mean drag coefficient, Strouhal number and the root-mean-square values of drag and lift coefficients with Re and AR is presented for [Formula: see text] and 3. The current numerical computations yield that for both gap ratios and all Re, there exist four different flow regimes depending on AR: (a) steady flow, (b) modulated flow, (c) symmetric flow and (d) periodic flow. At narrow gap ratios, the jet flow emerging within the gaps of cylinders altered the flow structures and fluid forces abruptly. The aspect ratio is found to have more influence on the flow characteristics of cylinders as compared to the Reynolds numbers at large gap ratios.

Numerical Computations for Flow Patterns and Force Statistics of Three Rectangular Cylinders

“…Rahman et al [18] characterized the flow behind three side-by-side rectangular cylinders into deflected, bistable, flip-flopping, chaotic, symmetric and synchronized flow patterns. Steady, modulated, symmetric, and periodic flow patterns were reported by Rahman et al [19] for flow behind three side-by-side rectangular cylinders for different aspect ratios and Reynolds numbers.…”

“…It can also be deduced from the above discussions that Re, AR, and g affect the flow characteristics around side-by-side arranged cylinders. Some reference data are available for the effect of Re and spacing ratio for flow past circular or square cylinders in side-by-side arrangement, but there is one reference paper [19] available regarding the effect of Re for flow behind three side-by-side rectangular cylinders. e first aim of the present study is to analyze the effect of aspect ratio and Reynolds number on flow structure mechanism around the three side-by-side cylinders at g � 1.5 as it is a well observed fact that the flow becomes fully developed [14][15][16] at this spacing value.…”