Hydraulic properties of a bifurcated channel system with different bed slopes under sub-critical flow

摘要

This study investigates mainstream alternation by examining the hydraulic properties of a bifurcated channel on a flat bed and on a movable bed, under sub-critical flow. We consider a bifurcation model and apply momentum equations to it. The results show that the system has two solutions for discharge ratio r. one for sub-critical flow, and the other for super-critical flow. We performed flat-bed and movable-bed experiments. The flat-bed experiments showed that the discharge ratio r remains constant during each run, a result that agrees fairly well with the theoretical solution under sub-critical flow. The theoretical solution means that discharge into the steeper channel branch is greater than that into the other channel. The movable-bed experiments showed that r oscillates with time for each run. And mainstream alternation occurred only in one Run which bed form is dune.