ABSTRAKT

The present work uses laser Doppler anemometry and an optical microsensor to characterize the transitional flow in regions where abrupt changes in surface momentum flux occur due to changes from one extensive uniform rough surface to another extensive uniform smooth surface. The work analyzes the statistics of the flow to show that the velocity gradient method and Preston tubes of cannot be used to determine the wall shear stress. Reference skin-friction data is then provided by the optical microsensor.