Abstract
Measurements of mean velocity throughout a layer and surface pressure around a rough surface have been performed to investigate the effect on three-dimensionality of a roughness element due to micro-grooves. All experiments were made at a unitary Reynolds number of 6.24 x 105 (m-1) and in zero pressure gradient. The representative scale normalized with an averaged roughness height has little effect of the three-dimensionality of the rough surface. The pressure drag coefficient has almost same value with that of a two dimensional rough surface. Roughness function can be represented as a function of the Reynolds number based on the representative roughness scale, and the intercept term of the function depends on the three-dimensionality of the rough surface.
