Evaluation of synthetic sponge to control wave-induced currents in coastal waters.

Based on National Oceanic and Atmospheric Administration (NOAA) Coral Reef Conservation Program, climate change causes coral bleaching. In response to the high roughness of coral colonies and reduced current velocity, coral reefs in near-shore regions are susceptible to accumulation of pollutants or sediments. This threatens coral reef ecosystems and causes several challenges. Controlling the wave velocity, Turbulent Kinetic Energy (TKE), and vortical structures help enhance advection/diffusion of particles from coral reef zones. In the current study, a device inspired by a marine sponge (synthetic sponge), was designed. A suction/pumping function was devised through two concentric perforated cylinders to simulate this mechanism in the synthetic sponge. Several physical and numerical experiments (using OpenFOAM software considering RANS modeling) were carried out to investigate the effects of geometrical characteristics (i.e., cylinder and perforation diameters) of synthetic sponge on wave hydrodynamics. Accordingly, wave attenuation, mean horizontal and orbital velocities, turbulent kinetic energy, and vortex structures were evaluated. In summary, the results indicated that the pumping flow can act as an energy recovery downstream of the sponge, and the horizontal velocity and TKE growing in the water column due to generation of special vortices. Therefore, the current synthetic sponge can improve momentum transfer. • Perforation diameter has 60% contribution to the mean velocity in the mid-depth. • The small annular space traps water through the two concentric cylinders. • The secondary flow generation annihilates the spiral and turbulence of flow. • The pumping flow acts as a wave energy recovery in the downstream. [ABSTRACT FROM AUTHOR]