Nondimensional Parameters Governing Hyperconcentrated Flow in a Open Channel

Abstract

Nondimensional parameters governing rapid hyperconcentrated flows are derived by the comparison between intergranular-stress and inertia terms in the momentum equation. It is found that the ratio of flow depth to grain diameter and volumetric concentration of grains for the estimate of friction forces acting on a bed, and the ratio of tube diameter to grain diameter and concentration for that of drag forces on a tube are important parameters.
Relationship of friction and drag coefficients to these parameters is investigated experimentally. Dependence of drag coefficient on concentration and nondimensional tube diameter is found similar to that of friction coefficient on concentration and nondimensional depth.
For the larger concentration and smaller ratio of a characteristic length to grain diameter intergranular interactions play dominant role. For the larger ratio, on the other hand, the effect of turbulence of the hyperconcentrated flows becomes major.