Abstract
The inner layer and outer layer of unsteady smooth open channel flows were measured by making use of a twocomponent laser Doppler anemometer (LDA) under the condition that the unsteadiness parameter is very high. In such a situation the von Karman constant decreases in the rising stage and decreases in the falling stage. The friction velocity evaluated from the log law does not coincide with that evaluated from the linear formula in the viscous sublayer with an increase of the unsteadiness. In contrast, the characteristics of normalized turbulence are not affected by the unsteadiness so much; the van Driest's damping factor of the turbulence intensity of the streamwize is almost constant against the normalized time. The third-order moments of the turbulence agree well with those of the steady uniform flow.
