NUMERICAL STUDY ON VISCOUS SHEAR-FLOW PAST A CIRCULAR-CYLINDER

Numerical solutions of the unsteady Navier-Stokes equations are presented for a two-dimensional flow past a circular cylinder immersed in a uniform shear flow. Several values of the shear parameter K defined as Ga/U// infinity are employed, where a is the radius of the cylinder, G is the transverse velocity gradient and U// infinity is the oncoming velocity at the Center of the cylinder. The Reynolds number Re based on 2a and U// infinity is assumed to be 40 and 80. Although a pair of steady-standing vortices is formed in a uniform flow when Re equals 40, it is found that a periodic vortex shedding occurs at the same Reynolds number in the case of a shear flow with a shear parameter K equals 0. 025. When the shear parameter becomes as large as K equals 0. 2, however, the vortex shedding is suppressed even in the case of a shear flow revealing a clearly asymmetric flow pattern with respect to the geometrical center line of the cylinder. The same tendency is also observed in the flow of the Reynolds number Re equals 80. The time-averaged lift force acts in the direction towards the high-velocity side of the shear flow and its magnitude is approximately proportional to the shear parameter.