Effect of gap spacings on flow past row of rectangular cylinders with aspect ratio 1.5

Two-dimensional numerical study has been carried out to investigate the effect of gap spacings for flow past five side-by-side rectangular cylinders using the lattice Boltzmann method at a Reynolds number of 150 and aspect ratio defined as AR=length/height=1.5. The gap spacing between the cylinders is varied systematically from g=0.5 to 4, so that the sensitivity of the flow and force statistics can be inspected. The gap spacings have strong effect on the hydrodynamic interaction of the cylinders wakes which significantly affects the flow structure. The flow behavior can be grouped into five patterns: (i) symmetric, (ii) flip-flopping, (iii) in-phase and anti-phase modulated deflected, (iv) in-phase modulated non-synchronized and (v) in-phase and anti-phase modulated synchronized. Calculations of mean drag coefficient, Strouhal number and root-mean-square value of drag and lift coefficients are carried out on each cylinder and compared with available literature. Each flow pattern will be studied in terms of wake structure, power spectra analysis of lift coefficients and time analysis of drag and lift coefficients. The average Strouhal number and average drag coefficient show significant variation against gap spacing.