Coherent Structure of a d-Type Rough Wall Boundary Layer in a Fully Rough Regime : Results with the Four-Quadrant Analysis

Coherent Structure of a d-type rough wall boundary layer at a fully rough regime has been investigated with the four-quadrant analysis. Fractional stress contribution of the events associated with the bursting phenomenon was quantitatively analyzed and compared with the results at a low Reynolds number. The fractinal stress contribution of the second quadrant (ejection event) decresses with increasing the Reynolds number. The contribution of the violent events was studied and the significant difference of the turbulent structure among d-type rough, k-type rough and smooth wall flows was found.