The effects of shear on vortex shedding patterns in high Reynolds number flow - An experimental study

An investigation of the effects of shear on vortex shedding is presented. Vortex shedding is a potential major source of loading on the OTEC plant cold water pipe and the effects of shear on vortex shedding were studied in high Reynolds number flow. The existence of vertical shear in ocean currents leads to the presence of discrete cells distributed along the pipe, whose relative frequencies and phasing can significantly affect the dynamics of the pipe. Tests were made using stability wind tunnel facility, a 6 in diameter aluminum cylinder, and series of wire screens to simulate the shear and flow turbulence characteristics. The surface pressure distribution on the cylinder indicated that the mean pressure pattern is independent of the amount of shear in the upstream flow, but shear is an important factor in determining the range of pressure fluctuations. The eddy shedding frequency measurements substantiated the existence of two or more cells of constant shedding frequency along the length of the cylinder when it was subjected to upstream sheared flow.