Interaction between a bubble curtain with waves and currents: implications on sediment dispersal

Bubble curtains are widely used for different environmental applications relying on the generation of recirculation cells. Prior studies suggest that bubble curtains can modify the morphology of rivers and channels by keeping sediment in suspension, and as an alternative for sediment transport control. However, their use in coastal environments is still relatively unexplored. We investigate the interaction between the recirculation cell induced by a bubble curtain with incoming currents and waves. Laboratory experiments were carried out on a wave-current flume facility equipped with a bubble diffuser. Simulated cases considered different characteristics of the bubble curtain, water level, currents, and waves. Free-surface elevation and velocity were measured concurrently with high spatial resolution. Experimental observations show that the bubble curtain modifies wave- and current-induced velocity profiles. For unidirectional currents, as the flow approaches the curtain, the velocity magnitude decreases near the surface and increases near the bed due to the recirculation cell. In the presence of waves, the recirculation flow affects both the wave-induced velocity and asymmetry, both important parameters for sediment transport. Thus, synthetic particles were used as sediment proxy to investigate the role of the recirculation cell on the wave-induced near bed transport. Experimental results highlight the effects of both the bubble curtain recirculation cells and the structure of the diffuser itself in sediment deposition. These experiments reveal the potential of bubble curtains for modifying hydrodynamics and deposition patterns in coastal zones, and provide a novel data set which can be used for the calibration and validation of numerical models.