Higher-order turbulence statistics of wave-current flow over a submerged hemisphere

Higher-order turbulence characteristics such as turbulence production, turbulence kinetic energy flux, third order moments and velocity spectra associated with turbulent bursting events due to the influence of a submerged hemisphere under wave-current interactions are presented. The velocity components were measured using three dimensional (3D) 16 MHz micro-acoustic Doppler velocimetry (Micro-ADV). In the wave-current interactions, the contributions of turbulent bursting events such as ejections and sweeps significantly reduce in comparison to the current-only case. The distributions of the mean time intervals of ejection and sweeping events are found to alter due to the superposition of surface waves. Results also depict that the turbulence production in the wake region of the hemisphere reduces remarkably, due to the superposition of surface waves on the current. Further, spectral and co-spectral analysis demonstrates that there is a significant reduction of power spectral peak for both longitudinal and bottom-normal velocities upon superposition of surface waves, which signifies a remarkable change in energy distribution between different frequencies of waves.