Drag Reduction by Micron-Sized Distributed Surface Geometry on a Flat Plate.

Abstract

The present paper deals with experimental investigation using micron-sized distributed surface geometry on a flat plate in order to observe effective drag reduction. Namely, the objective is to verify Tani's hypothesis that distributed rough surface can even reduce turbulent drag in a certain Reynolds number range. So, we directly measured the net drag of a flat plate wrapped by a sheet with micro-sized distributed rough surface geometry. Obtained data showed that a limited amount of drag reduction is observed in the case of certain kinds of surface geometries. This result requires a new explanation of how the turbulent energy is suppressed in the turbulent boundary layer, since existing turbulent drag reduction mechanisms for a riblet surface is always explained together with streamwise groove structure. Therefore, by analyzing the obtained results, a more appropriate energy production mechanism in the turbulent boundary layer might be found out. The present experiment is the first step in a series of investigations concerning the above title.