Dispersion around a circular cylinder in surface wave motion

In this paper, we examine uid ow and associated dispersion around a circular cylinder under progressive surface wave motion. The ow field and vortex shedding patterns were studied using ow visualization and Particle Image Velocimetry (PIV). Several patterns of vortex shedding were identified around a single cylinder. The vortex shedding patterns under progressive wave motion are similar to those observed in planar oscillatory ow, except in the way the vortices form and in the orientation they take. The observed vortex patterns in progressive wave motion are more unstable than those in planar oscillatory ow. Using particle tracking and the Lagrangian dispersion method, the dispersion coefficients were calculated for various ow regimes. The observations confirm the calculations in general. It was also found that wave steepness can affect the shedding pattern. The vortices tend to shed more frequently in a wave direction at low wave steepness.