Study on Surface Vortices in the Composite Channel Flow by Means of Hydrogen Bubble Method

Abstract

It is well-known that periodic large suface-eddies are generated at the interface between the main channel and the floodplain in the overbank flow of a composite channel. In this paper. the 3-dimensional structure of the flow in the interfacial zone was observed by hydrogen bubble method. using a closed channel.
It is shown that. accompanied by the 2-dimensional large eddies. there exist inclined eddies rolling like longitusinal vortices near the top-edge of the floodplain. Though the flow pattern is 3-dimensional and very much complicated. it has intense periodicity with the large eddy structure. And it was found that this periodicity can be explained by 2-dimensional stability analysis of a free shear flow.