Plastron restoration by gas injection through super-hydrophobic surface created on porous material

In this work, we experimentally studied the plastron restoration by gas injection through super-hydrophobic surface created on a porous material . The SHS was created by sprayed coating a commercial super-hydrophobic coating on a porous steel plate. We found that the surface area being restored with a plastron increased with increasing gas injection pressure and gas injection duration. Using high-speed imaging, we found that the plastron restoration process involved bubble formation, merging and detachment. A layer of gas was left on the surface after bubble detachment. The size of the detached bubble increased with time due to bubble merging, and became stable when there was no more bubble merging. Increasing gas injection pressure led to higher gas flow rates, larger detached bubble sizes and faster plastron restorations. A plastron restoration within 0.3 s was achieved at the highest pressure, faster than the in-situ gas generation methods. Furthermore, we found that the gas flow rate through the underwater SHS can be described by a modified Darcy’s law. Our results highlighted the potential of using porous material and gas injection to restore the plastron and made possible the implementation of SHS in high-Reynolds number turbulent flows.