河床形態の変動特性に関する研究(2) ―閉管路移動床の実験から―

Abstract

To approach to phenomena of movable bed in open channel flows, especially char-acteristics of bed configuration and flow resistance, the fundamental experiments arecarried out by use of a closed channel with movable bed.Characteristics of bed configuration in closed channel flows are almost identical withthe results of experimental observations in open channel flows. Transitions from initialflat bed to undulation beds of ripple-dune type, and its break-down process are observed.On the basis of analytical results of the closed channel experiments, author discussesthe mechanisms of transion processes in open channel flows. Then, eixistence of freewater surface, I. E. Froude number, does not takes any part in break-down process ofundulation beds, but non-dimensional quantity u*2/(σ/ρ - 1)gd.And, To study the law of flow resistance of movable beds, author indicates thatentropical analysis to energy dissipation processes in open channel flows on movable bedmust be introduced.In last part of this paper, the tendencies of flow resistance in unsteady flows on movablebeds in the closed channel are described.