Underwater sound absorption characteristics of water-saturated porous materials

In this research, the underwater sound absorption performance of porous media saturated with water is investigated through long straight tubes (LSTs) with circular cross-section and sintered fibrous metals (SFMs) containing complex pores, and effective underwater sound absorption capability is demonstrated theoretically, numerically and experimentally. Specifically, the theoretical model for LSTs, verified by direct numerical simulations (DNSs), reveals that much smaller pore diameter and much larger layer thickness of porous material is needed to gain high waterborne sound absorption coefficient than to obtain large airborne sound absorption coefficient. Besides, to examine the sound absorption capacity of realistic porous materials, SFMs backed with a finite cavity are experimentally measured under 7 different hydrostatic pressures in a water-filled tube, and numerically characterized via multi-physics couplings. Insensitivity of effective sound absorption capability to high pressure is established, which stems from the different underwater wave energy consumption mechanism (i.e. viscous-thermal effect) of porous materials from conventional rubber kind of underwater sound absorption materials. Physically, porous materials possess great potential in developing the next generation of high-performance underwater sound absorption materials.