A two-dimensional lattice Boltzmann study of flow past five side-by-side rectangular cylinders

Numerical simulations are performed, in the range of 0.5 ≤ g ≤ 5, where g is the separation ratio between the cylinders at fixed Reynolds number 150 and aspect ratio 2, for flow past five side-by-side rectangular cylinders. A two-dimensional code is developed using the lattice Boltzmann method. The effect of separation ratio on the vortex shedding frequency, time-trace analysis of drag and lift coefficients, power spectra analysis of lift coefficients and force statistics exerted on the cylinders is quantified together with the observed flow structure. Five different flow structures were found and named as nearly symmetric (g = 0.5), flip-flopping (g = 1), modulated (g = 1.5), strongly interactive (g = 2, 2.5 and 3) and weakly interactive (g = 4 and 5) flow structures. It is found that the vortices are generated on the surfaces of the cylinders as width of the cylinder is 2h (h is the width of the rectangular cylinders) and due to this there is modulation in time-history analysis of drag and lift coefficients for all chosen cases except at g = 0.5. The Strouhal number is also calculated using Welch’s method for comparison, and correlation of lift coefficients for different combinations is also given.