Drag Reduction Devices for Marine Applications

Riblets, which essentially consist in stream-wise grooved surfaces, is a passive drag reduction technique whose effectiveness has been demonstrated by many experiments since the last century. The firm 3M & Co. produced riblets as plexiglass surfaces in the form of sticky tapes which have been used on sport sailing ships with a great success. Riblets dimensions (microns at high Reynolds numbers) make numerical simulations difficult to perform, indeed detailed flow features inside the grooves can be detected only by Direct Numerical Simulations (DNS), still unfeasible for high Reynolds numbers and complex configurations. To overcome this issue some models for the numerical simulations of riblets or superhydrophobic surfaces by RANS or LES have been proposed in the last decade. A method for the numerical simulation of riblets installed on complex configurations is here presented and applied to hydrofoils and three dimensional configurations.