Hideo Sasajima

Frictional Resistance of Wavy Roughened Surface

The roughness effect of the surface of ships has been measured by the scale of sand roughness calculated by Schlichting, but this seems meaningless because of the discrepancies between the nature of the painted surfaces and that of the sand roughened ones. The authors present here a theory of resistance of the wavy roughened surface, based on the mixture length theory containing the viscosity effects which is proposed before by the senior author in this institution.The numerical calculations for a circular pipe and a flat plate showed the variation of resistance coefficient with Reynolds number is nearly parallel to that of the smooth surface. A method is indicated to find the effect at large Reynolds number from a simple experiment of model plate.