Recirculation Region Control Behind a Partially Submerged Cylinder Due to Wave Against Current

This chapter shows the effect of wave acting against the current on the modulation of vortex shedding behind a partially submerged cylinder. The effect of superimposed wave against current flow on the drag field and turbulence characteristics at downstream of the cylinder is still not been revealed. A micro Acoustic Doppler velocimeter (ADV) is used to measure the high-frequency velocity variations. Observation suggests that there is no distinct recirculation in the wake region for the lock-on (LO) case. This LO state is achieved when the frequency of the superimposed wave is two times that of natural vortex shedding (Vns) frequency. Turbulent dissipative eddy creates a jacket around the cylinder that changes the flow separation due to the superimposed wave acting against the current. Further, the upward momentum flux is found in the LO case. As far as vorticity is concerned, it is completely different for LO case. Moreover, the mean flow, fluctuating velocity, and velocity derivatives interact and exchange energy in a complex way for the case of LO as evident from turbulence production. This complex interaction of energy enhances the drag force at the near bed region, which decreases toward the free stream region in the vicinity of the cylinder for LO case.