The relation between the coherent structure detected using wall shear stress fluctuations and wall shear stress distribution: 1st report (ejection event case)

摘要

In order to clarify experimentally the relation between wall shear stress fluctuations and near wall flow field when ejection events occur, three velocity components and wall shear stress are measured simultaneously using laser doppler velocimeter and using the flush-mounted hot film probe. Time-variation of ensemble averaged flow fields when ejection events occur is examined. Also time-variation of ensemble averaged wall shear stress distributions is examined by simultaneous measurements of streamwise velocity in the viscous sublayer and wall shear stress. Consequently, it is clarified that ejection events detected using wall shear stress fluctuations are induced by the counter rotating streamwise longitudinal vortices and change of the wall shear stress distribution is closely related to the passage of streamwise longitudinal vortices.