EFFECTS OF CROSS ANGLE BETWEEN WAVE AND CURRENT ON THREE-DIMENSIONAL FLOW FIELDS AROUND A CYLINDER

摘要

This paper presents the results of a numerical investigation on three-dimensional flows around a vertical cylinder in wave and current. The flows are simulated by using the Navier-Stokes equations expressed in a generalized curvilinear coordinate system. Descriptions are given of vortex-flow features around the cylinder base. Examinations are made on the effects of cross angle between wave and current, Keulegan-Carpenter number, KC, and coexisting current ratio, V_r, on the vortex motion. It is shown that the scale of the horseshoe vortex decreases with increasing cross angle, while its lifespan in one wave period increases. The effects of the current ratio on the size and the lifespan of the vortex are as important in the case of wave propagating perpendicular to the current as in the case of the codirectional wave and current. The bed shear stress is also investigated in detail. The amplification of the bed shear stress is heavily influenced by the cross angle, KC and V_r. The results show that the maximum shear stress tends to decrease with increasing cross angle and the decrement factor is large for large KC and V_r.