Mechanism of drag generation by surface corrugation

Drag generated by periodic corrugation has been determined analytically in the limit of long corrugation wavelength. Three physical mechanisms have been identified, i.e., the additional shear drag due to an increase of the wetted area and the re-arrangement of the shear stress distribution, the pressure form drag associated with the mean pressure gradient, and the pressure interaction drag associated with the phase difference between the surface geometry and the periodic part of the pressure field. The total drag increases rapidly with increase of the corrugation amplitude, with the form and interaction drags contributing up to 45% and 30% of this increase, respectively. (C) 2012 American Institute of Physics. [doi:10.1063/1.3675557]