Experimental Investigation of Force Coefficients for Groups of Three and Four Circular Cylinders Subjected to a Cross-flow

This paper has investigated the flow interference between three circular cylinders of equal diameter in an equilateral-triangular arrangement and also between four circular cylinders in a square arrangement when subjected to a cross-flow. Wind tunnel experiments were conducted to measure force coefficients for six spacing ratios () varying from 1.5 to 4 at subcritical Reynolds number of. The pressure distributions on the surface of the cylinders were measured, using pressure transducers. It was found that for three cylinders at, the upstream cylinder experiences lower mean drag coefficient than that of the downstream ones. Also, the minimum drag coefficient values of the downstream cylinders occur at and. Moreover, It was revealed that for four cylinders at, due to severe flow interference between cylinders, there is a difference between lift coefficients for the upstream cylinders. Also, for, the mean drag coefficients for downstream cylinders are negative. In addition, it was concluded that the variations in strongly affect the aerodynamic coefficients. Also, by decreasing, the effects of the flow interference between the cylinders increase.