移動床開水路の抵抗則に関する研究(1)

Abstract

This paper describes the results of the study on the friction factors for flow in movable bed channels.The authors investigate the flow pattern on sand waves by measuring the velocity distribution on a artificiallyfixed sand waves bed in order to obtain an analytical model for friction factor. As the result, the analysisby dividing to the energy slope into components due to form resistance and friction resistance can beaccepted. The flow on a bed with sand waves is similar to the one over a negative step. Therefor, by usingan equation of momentum form resistance can be expressed by a function of Fr, H/hm and L/hm, where Fr:Froude number, hm: mean depth and H, L are representative height and length of sand waves respectively.In a movable bed the values of H/hm and L/hm changes with varing flow conditions and sediment characte-ristics. Using the present knowledge about the relation between the geometries of sand waves and flow con-dition friction factor due to form resistance is expressed by a function of τ*(= υ*2/sgd) with parameters Iand d, which is discussed by the various experimental data.