The influence of ship wave on turbulent structures and sediment exchange in large shallow Lake Taihu, China

Turbulent burst plays a key role in momentum transfer and sediment movement in large shallow lakes. This study addresses the quantitative influence of ship wave on turbulent structures, momentum and sediment fluxes in Lake Taihu, a large, shallow eutrophic lake that experiences heavy shipping traffic. Acoustic Doppler Velocimeter (ADV) and Optical Backscatter Sensor (OBS) were used to obtain high-frequency flow velocities and suspended sediment concentration (SSC) data before and when a cargo ship passed by. We found that ship waves mainly propagate along the horizontal direction. The near-bed turbulent bursting events with ship disturbance increased by 8.42%. Consequently, the vertical momentum and sediment fluxes were increased by 3.4 times and 8 times, respectively. In terms of bursting processes, ejection and sweep possess much stronger capacity in carrying sediment and are largely controlled by the disturbance in the vertical direction, while inward and outward interactions are mainly affected by horizontal disturbance. These findings represent an important step towards understanding the mechanism and effect of turbulent bursting under ship disturbance, and pave the way to future research in order to manipulate turbulent dynamics.