Formation and Reversal of Vortices around Circular Cylinders Subjected to Water Waves

Flow around circular cylinders has been studied for more than a century, but the mechanism of vortex shedding remains a puzzle. The basic feature of the phenomenon is the formation of vortices in the near wake which are shed alternately from either side of the cylinder and flow downstream to form the well-known kármán vortex street. Corresponding pressure fluctuations on the cylinder surface give rise to fluctuating lateral lift force. The free steam flow may be generally either with a constant velocity, accelerating form zero, decelerating to zero, but the vortex formation and the alternate vortex shedding follow a similar pattern. There are two fundamental differences when the circular cylinder is subjected to a progressive water wave. This study employed a three-dimensional setup because flow visualization was very simple to observe on the water surface. The main tasks have already been, or are being formed. It is expected that the results are also applicable to two-dimensional flows.