EXPERIMENTAL STUDY ON BAR FORMATION UNDER UNSTEADY FLOW CONDITIONS

Abstract

In the previous researches on the sand bed stability with finite amplitude and growth of alternate bars, it is assumed that flow changes over time due to the unsteady flow do not affect the generation of alternate bars. Hydraulic experiments on the formation of alternate bars under unsteady flow conditions are conducted in this paper. The wavelength and wave height of alternate bars differ significantly between unsteady and steady flow conditions and between rising and falling stage of the water level due to the flood wave. Unsteadiness is typical of actual formative conditions for alternate bars, especially for gravel bed rivers. Results suggest that finite amplitude effects of the flood-wave on alternate bar formation are not negligible when investigating their behavior under unsteady flow conditions.