Vortex Shedding From Bluff Bodies in a Shear Flow: A Review

This paper examines the effects of velocity shear on vortex shedding from stationary and vibrating bluff bodies. Experiments with circular cylindrical bodies and other cross sections such as D-section cylinders and rectangular cylinders, which were limited to conditions with length/diameter ratios less than L/D = 15 to 20, have shown that the spanwise cellular structure of the vortex shedding is dependent upon end conditions. The vortex shedding also is influenced strongly by the shear flow steepness parameter β¯ which is based upon the incident flow velocity gradient. Experimental evidence is available to show that moderate shear levels of practical importance (β¯∼0.01 to 0.015) do not appreciably decrease the probability of occurrence of vortex-excited oscillations for flexible structures and cables. The effects of incident shear on vortex shedding from stationary and vibrating bluff structures in both fluid media should be investigated further for long cylinders which have minimal end boundary effects. More definitive bounds for and details of this fluid-structure interaction are needed for applications in the wind engineering design of buildings and structures, and in the design of marine structures and cable systems.