Variation of wake patterns and force coefficients of the flow past square bodies aligned inline

Abstract

In this numerical study, the variation of wake patterns and force coefficients of the flow past four square bodies aligned inline are investigated. A two-dimensional numerical code is developed using the Lattice Boltzmann method (LBM) for this study. The code is first validated for the flow past a single and two tandem square cylinders. The results are compared to those available in literature and found to be in good agreement. After validation the calculations are further performed to investigate the effect of gap spacing (g) for the flow past four inline square cylinders at two different Reynolds numbers (Re) 100 and 200. The gap spacing is chosen in the range 0.25 ≤ g ≤ 7. Six different flow patterns: Single slender body, alternate reattachment, quasi steady reattachment, intermittent shedding, chaotic flow and periodic flow are found in this study with successive increment in spacing. It is found that some flow patterns existing at Re = 100 do not exist at Re = 200. The generated vortices at Re = 200 are much stronger as compared to those at Re = 100. The spacing value g = 3 is found to be critical at Re = 100 while at Re = 200 the spacing value g = 2 is critical due to abrupt changes in flow characteristics. At some spacing values the downstream cylinders have higher values of average drag coefficients as compared to upstream ones. In general the upstream cylinder (c1) have higher drag forces at Re = 200 than at Re = 100. The root mean square values of lift coefficient are found to be greater than the corresponding root mean square values of drag coefficient.