Turbulence Over a Pair of Submerged Hemispheres in Presence of Surface Waves and Following Current

The paper presents an experimental study in a laboratory flume to investigate the combined wave-current flow over a pair of hemispherical obstacles placed at a relative spacing L/d = 4, where L is a center to center distance between the obstacles and d is the obstacle height. Detailed velocity data were collected using three-dimensional micro-acoustic Doppler velocimeter from upstream to downstream of the pair of obstacles along the centerline of the flume. This study examines the mean flows, eddy viscosity, mixing length, turbulence kinetic energy (TKE) flux under the influence of two hemispherical obstacles in combined wave-current flow conditions. The analysis reveals that higher level of turbulence including maximum eddy viscosity and TKE flux is observed near the top of the obstacles. Further, the power spectral density (PSD) for velocity fluctuation is also analyzed to study the internal structure of turbulence due to combined wave-current flow over hemispherical obstacles.