Evaluation of particle adhesion on straight shaped riblets in a turbulent channel flow

Abstract

Riblets are micro-grooved structures on the object surface, and it is known that the skin friction drag can be reduced by approximately 10% with the riblets designed to have appropriate size and shape against the near wall turbulence. As for improving the operational durability of riblets, it is necessary to mitigate degradation of the drag-reduction effect. One of the main reasons of decrease in performance is particle clogging on the riblet groove. Although the particle motion near the riblet groove has been studied, the mechanism and characteristics of the particle adhesion have not been fully clarified yet. In the present study, we aimed to clarify how particles accumulate on the riblet grooves. As a preliminary experiment, the riblet plate was exposed in an atmospheric environment. The location and the size of the particles were identified by image analyses. It is found that the most of particles have diameter less than 15 μm, and particles are preferentially found in the corner of the riblet edge. A wind-tunnel experiments are planned to clarity the characteristics of particle adhesion on the riblet surface.