Wavy riblets for turbulent drag reduction

Abstract

A combined numerical and experimental study is carried out to investigate the capability of sinusoidal riblet patterns to reduce turbulent drag. In contrast to conventional straight riblets, sinusoidal riblets are able to induce a small amount of lateral motion in the ow. Therefore, they are thought to emulate the eect of lateral wall oscillations and hence to achieve a higher reduction of turbulent drag than straight riblets. This parameter study shows that lateral velocity oscillations are successfully induced. Positive eects of small geometric amplitudes are weak and could not be determined outside the uncertainty range of the measurements or simulation statistics. Larger amplitudes lessen the overall drag reduction which is mainly due to increasing pressure drag.