Numerical investigation of flow around square cylinder with an upstream control plate at low Reynolds numbers in tandem

Abstract

The study focuses on the effect of gap spacing (g) ranging g = 1–7, Reynolds numbers (Re) ranging Re = 80–200 and the size of the control plate (w) varied from 0.1d to 1d (where d is the size of the main cylinder) on the flow around a square cylinder with an upstream control plate. Two-dimensional multiple-relaxation-time lattice Boltzmann method is used to find the optimum condition, where the maximum reduction in drag force and suppression of vortex shedding occurs. It is observed that the drag is reduced significantly and the fluctuating lift is also suppressed. The detailed wake structure mechanism within gap spacing and near wake vortex structures around and behind the main square cylinder in the presence of the control plate are studied and compared with a plain square cylinder. In this study, the optimum conditions for maximum drag reduction in terms of control plate width, gap spacings and Reynolds numbers are found. The single bluff body, shear layer reattachment, critical flow, two-row single bluff body, fully developed two-row vortex shedding and quasi-steady-flow patterns are found. The time-trace analysis of drag and lift coefficients, power spectra analysis of lift coefficients, variation in force statistics and inclination angles are discussed in detail for all observed flow patterns. The maximum reductions on the drag force are 99.82, 99.8, 99.8, 99.9, 99.98, 100.4, 100.1, 100.05 and 100.1% for Re = 80, 100, 120, 140, 150, 160, 180, 190 and 200, respectively.