NUMERICAL SIMULATION OF SPACING EFFECTS ON THE FLOW PAST TWO 2:1 RECTANGULAR CYLINDERS IN TANDEM AT Re=200

The time-periodic flow over two rectangular cylinders in infinite medium is numerically investigated in this paper using the newly developed multidomain pseudospectral method. The two cylinders are arranged in tandem and both with length-to-width aspect ratio of 2; the incoming flow is assumed to be laminar and uniform, and the Reynolds number based on the cylinder width and the freestream velocity is fixed at 200. Computations are focusing on the effects of S, the ratio between the streamwise spacing of two cylinders (gap length) and the cylinder width, on the vortex shedding formations, evolving patterns and related aerodynamic performances of cylinders within the range 1 <= S <= 10. Numerical results reveal that as S increases, there exists a critical value, S-cr = 5, at which the mean drag coefficients of both cylinders behave notable jumps, and the root-mean-square values of lift and drag coefficients reach maxima. Meanwhile, the vortices behind the two cylinders are shedding in anti-phase mode at S-cr, and their evolving patterns are further analyzed and interpreted.