Drag Reduction Of Turbulent Boundary Layer Over Air-Fed Superhydrophobic Structured Surface

Air-fed superhydrophobic blade riblet (ASBR) and triangular riblet (ASTR) structures were designed to recover the underwater air layer under controlled air supply pressure. Experiments in a gravity-driven water tunnel show that both structures reduce turbulent boundary-layer skin friction within the tested Reynolds-number range. Under constant air supply pressure, the drag reduction rate first increases and then decreases as Reynolds number increases; increasing the air supply pressure replenishes the air layer and improves drag reduction when the air layer remains intact.