Regularization of Wall-wall Turbulence by Discrete Roughness Element

This paper deals with an experiment effort on regularizing the near-wall flow-field of a zero-pressure-gradient turbulent boundary layer via passive discrete roughness elements. The major concept is to introduce quasi-steady wake of spanwise-aligned roughness elements into the near-wall region of wall turbulence, so that the mean spanwise spacing of low-speed streaks in the near wall region can be modulated.