The Effect of Free Surface on the Vortex Shedding From Inclined Circular Cylinders

Abstract

Spectral analysis of laser Doppler velocimetry measurements and flow visualization are employed to study the wake of inclined cylinders piercing a free surface. The results indicate that the free surface affects vortex shedding almost two to three cylinder diameters below the free surface. Variation of the vortex axis inclination and cells of shedding were visually observed. These effects induce a phase difference in the vortex-shedding mechanism. Streamwise vortical structures are formed along the primary vortex axis. Furthermore, for the case of the highest Froude number, evidence is provided that vortex shedding is suppressed in the region near the free surface.