Transition from steady to unsteady state flow around two inline cylinders under the effect of Reynolds numbers

Numerical computations are carried out to analyze the transition in flow states around two inline square cylinders under the effect of Reynolds numbers ( Re ). For this analysis, Re is varied from 1 to 110 at a fixed spacing ratio g = 3.5. The results are presented in the form of vorticity contours, streamline graphs, temporal histories of drag and lift coefficients and power spectrum of lift coefficients. Also the physical parameters like average drag coefficient, Strouhal number and the root-mean-square values of drag and lift coefficients are presented as a function of Re . Three different states of flow are found in this study by systematically varying Re : (a) steady state, (b) quasi-unsteady state, and (c) unsteady state. The points of separation and reattachment of shear layers depend on Re . This study shows that the values of physical parameters strongly depend on flow states and change their behavior when flow mode changes from one state to another. A significant reduction in the values of flow induced forces found due to the presence of two cylinders in the flow field when compared to single cylinder values. The results of the present study are also compared with the available data of other researchers and found to be in good agreement.