A theoretical prediction of friction drag reduction in turbulent flow by superhydrophobic surfaces

We present a theoretical prediction for the drag reduction rate achieved by superhydrophobic surfaces in a turbulent channel flow. The predicted drag reduction rate is in good agreement with results obtained from direct numerical simulations at Re-tau similar or equal to 180 and 400. The present theory suggests that large drag reduction is possible also at Reynolds numbers of practical interest (Re-tau similar to 10(5)-10(6)) by employing a hydrophobic surface, which induces a slip length on the order of ten wall units or more. (C) 2006 American Institute of Physics.