Wave-induced turbulent flow over the rubble mound of immersed structures with different shapes

This paper presents the turbulent flow dynamics over the rubble mound generated by regular waves propagating over submerged rectangular, quarter- and semi-circular structures. Particle image velocimetry was used to measure the wave-induced instantaneous velocity fields. As shown in period-averaged velocity fields, the weatherside vortices are formed when wave troughs pass over immersed structures. A small period-averaged recirculation cell is formed at the weatherside toe. Moreover, a stronger period-averaged recirculation cell is developed in the vicinity of the weatherside corner of the rectangular structure than quarter- and semi-circular submerged structures. The leeside vortices are generated by the passing wave crests. A pair of counter-rotating recirculation cells are formed downstream while a shelter area from turbulent flow exists above the leeside berm. The evolution of phase-averaged vortices behind the rectangular structure is mainly confined to the vicinity of leeside wall while those behind the quarter- and semi-circular structures are advected horizontally further downstream. These observations indicate strong asymmetry of surface elevations and velocity fields due to the interference of immersed structure in the global advection of wave-induced flow. Consequently, the resulted asymmetric flow is expected to induce local scouring and pulsating pressures on immersed structures. It was also found that the geometry of immersed structure has a significant impact on the advection and dissipation of vortices.