PÉCLET NUMBER ON THE FORMATION PROCESS OF SANDBARS

Abstract

 Many studies have been conducted on spontaneously formed sandbars in rivers where the bed material consists of sand and gravel, but the physical mechanism of their formation has not yet been clarified. In this study, we measured the bottom and water surface of a single row of sandbars at the time of their formation using ST, calculated the flow velocity by plane two-dimensional analysis, and calculated Pe, which is the ratio of advection to diffusion. We found that there is a close relationship between Pe and the geometry of the bottom surface, and that the histogram of the x-component of Pe is bimodal. In particular, the distribution of the histogram changed at a constant value in the early stage of sandbar formation, regardless of the conditions. These results suggest that the large Pe during the formation process of sandbars is due to the fact that the advection of sandbars outweighs the diffusion of sandbars, and that the wave height of riverbed waves develops due to this equilibrium relationship.