固液混相開水路流れの水理特性に関する研究 (1)

Abstract

This paper deals with characteristics of the resistance coefficient and the vertical distributionsof velocity and concentration of free surface shear flows with suspended sand particles, as a firststage of research program for hydraulics of multi-phase flows.Main results obtained through the experimental investigation are as follows; 1) The resis-tance coefficient of a sediment-laden flow over smooth bed increases with, while that of a flow overrough bed decreases, with increasing of sediment concentration. 2) The vertical distribution ofmean velocity in the outer region is confirmed to be logarithmic for a sediment-laden flow as sameas a clear water flow. 3) It should be noticed that, in a sediment-laden flow over smooth bed, decreasing of velocity near the bed results larger velocity gradient compared to a clear water flow, and that, in a sediment-laden flow over rough bed, increasing of velocity near the free surfaceresults larger velocity gradient. 4) The Karman constant of sediment-laden flow over bothsmooth and rough beds becomes larger than that of a clear water flow. The integral constant of alogarithmic velocity distribution for a flow over smooth bed decreases with increasing of sedimentconcentration, but that for a flow over rough bed increases with increasing of sediment concentra-tion. 5) The characteristics of turbulence of a sediment-laden flow is also changed from thatof a clear water flow, especially in the region near the bed, where the turbulence intensity andthe energy dissipation rate become larger. 6) Non-uniform lateral distribution of sedimentconcentration may be described by the connection with large-scale turbulent motion such as asecondary flow. That is, high and/or low speed streaks are seemed to correspond with low and/orhigh sediment concentration, and these characteristics should be more investigated in details.