The Turbulent Model And It's Application To The Sediment-laden Two-phase Flow

Based on the two-phase flow theory, the turbulence theory and the kinetic mechanics theory of sediment, a turbulent model of the sediment -laden two-phase flow is developed. The kinetic characteristics of the water and sediment in the zone where conies under the influence of bottom outlet for discharging sediment is emphatically discussed.The difficulties on studies of the diffusion coefficient for suspended particles in solid-liquid two-phase flow are pointed out. The author establishes the Project Pursuit Model(PPM) which is based on the two-phase flow theory and the stochastic theory. It has shown that the results by PPM accord with the experimental data well. The kinetic characteristics of sediment-laden flow and the mechanism of the turbulent suspension near the wall is theoretically analyzed. The author suggests that the wall function in which the effect of pressure gradient on the velocity distribution near the wall should be considered. Contrasting with existed methods on studying the kinetic characteristics of the sediment-laden two-phase flow, the author argues that the proposed model in this dissertation is more advantageous and reasonable than them. For the fist time, a new ideal is put forward that the slip velocity between phases consists of advection velocity and drift velocity. Theoretically, it brings certain possibility for further study of kinetic characteristics of the sediment-laden flow. It has shown that the drift velocity is relatively more intense near the wall which greatly affects the turbulent suspension and transportation diffusion of the sediment. Comparing with other multiphase models, the author deems that the velocity difference between the two phases is the main reason for giving rise to the slip and the turbulent diffusion drift has a lesser effect on the slip.The author applies the turbulent model of this paper to the example in the* The project is supported by the Ministry of Education (99203).experiment by Coleman. It is shown that the calculated results accord well with the experimental data. It is also applied the model to a 3-D flow zone where conies under the influence of bottom outlet for discharging sediment to see the characteristics of sediment-laden flow and the configuration of erosion funnel. It is shown that the concentration of sediment and its gradient are smaller near water surface and relatively larger close to the wall along the vertical direction. Especially, the concentration gradient of sediment is greatly larger near the wall. This phenomenon would affect the velocity distribution in the same zone.It is shown that the velocity distribution of sediment-laden flow obeys the exponential or logarithmic law in the zone far away from the bottom outlet. However, within the zone where comes under the influence of the bottom outlet the velocity distribution is more different from that in the zone far away from the outlet. The slip velocities occur both in the vertical and horizontal directions in the influenced zone by the bottom outlet. In the existed mathematical models of sediment-laden flow, only the vertical settlement is considered and the slip movements in another directions are ignored. It can be considered that those models have to be confined to apply to the zones where the turbulence is fully developed. Moreover, the settlement velocity of sediment within the zone of erosion funnel is smaller than it in the quiescent water. So it is not reasonable in the turbulent flow if the variation of settlement velocity with time and space is not considered or it is replaced by the settlement velocity in the quiescent water.Based on the analyzing methods of the Engineering Sediment, the results of mathematical simulation for the erosion funnel's terrain have shown that the terrain of the erosion funnel is related to the shape and location of the bottom outlet, and the operation manner of the reservoir as well as. If the zone is more closed to the bottom outlet, the erosion of the funnel is more intense both in the vertical and horizontal...