ENERGY LOSS OF PIPE FLOWS STRATIFIED WITH SUSPENDED-LOAD AND BED-LOAD

The problem of energy loss for pipe flows stratified with suspended-load and bedload is discussed in this paper. It is postulated that for two-phase flows with coarse particles at high concentrations, the impact force on particles plays an important role in suspending the particles. On this basis, formulas for friction coefficients are derived and substantiated by the measured data. Experiments reveal that the classical diffusion theory is not sufficient for describing two-phase flows with coarse particles at high concentrations. Whether the suspension of coarse particles increases the dissipation of flow energy mainly depends on the relative importance of the impact force as compared with the turbulent force acting on the particles. However, at high concentrations of coarse suspensions, dissipation of flow energy will be increased significantly. The presence of bed-load will undoubtedly increase the energy loss of the flow. A quantitative relationship for additional loss due to the presence of the bed-