Effect of relative spacing on wake turbulence under wave-current flow
This paper reports the findings of an experimental study carried out in a laboratory flume to investigate the interaction of a surface wave with a unidirectional current over submerged tandem (bed mounted two in-line) hemispheres. The pitch-to-height ratio of the hemispheres was varied to spawn d-type (L/d = 2), intermediate (L/d = 4), and k-type (L/d = 8) relative spacing. The observations are focused on the changes induced in the mean velocity, turbulence intensity, Reynolds shear stress, and the frictional contributions of burst-sweep cycle to shear stress due to superposition of surface waves on the ambient flow. The consequences from the present experiment showed that the stream-wise velocity fluctuation follows the normal Gaussian distribution at upstream of hemispheres. Further, the joint probability density function showed that the superimposed surface waves on the current are capable of modulating the turbulent eddies with a larger band of energy and frequency spectrum compared to current-only flow.