A224 砂粒子を高濃度に含む流れに及ぼす砂粒子径の影響(A-22 河川における移動床流れ(2),一般講演)

概要

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Results obtained from both of flume tests and theory suggest that an equilibrium bed slope in flow over an erodible bed is determined only by sediment discharge rate when the movements of sediment particles are laminar and thus no suspended transportation take place. This means that the static friction force is dominant in debris flow and that sediment concentration is determined by shear stress balance on the bed surface; i.e., the external shear stress must be equal to the static shear stress of sediment particles, as seen in our previous studies. On the other hand, if part of sediment particles in debris flow body is transported in suspension, sediment concentration will be larger in comparison with that in case of laminar motion of sediment particles and the equilibrium bed slope will decrease. These facts are supported Egashira et al.'s experimental data. The present study discusses an influence of flow scales on an equilibrium bed slope and flow structure experimentally and theoretically. Data of equilibrium bed slopes and velocity profiles obtained in flume tests are analysed for this study. Those results emphasize that the equilibrium bed slope decreases with increasing of flow scale if part of debris flow body is turbulent, and it is predicted corresponding to increase of mass density of fluid phase.
日本流体力学会の論文
2004-08-09