Viscous Forces Acting on a Horizontal Circular Cylinder in Regular and Irregular Waves

Abstract

In the present paper, wave forces acting on a horizontal circular cylinder are investigated. The results of experiments in regular waves demonstrate that a circulating flow exists around the cylinder and causes the force orthgonal to incident velocity of fluid particles. This force always reduces the inertia force. The results of a simulation of the vortex shedding flow around the cylinder demonstrate that much larger scale of vortex shedding that in plane oscilatory fiow occures in regular waves even in low Kc number, and the shed vortices create the circulating flow around the cylinder. From results of experiments in irregular waves, it is found that the reduction of inertia forces in each wave cycle seems to be greatly affected by the amplitude of the previous cycle. The memory effect on the circulating flow is comfirmed by the simulation of the vortex shedding flow in irregular waves.