【作者】 周新民；

【导师】 赵文谦；

【作者基本信息】 四川大学 ， 水力学及河流动力学， 2002， 博士

【摘要】 本文从两相流理论、紊流理论和泥沙运动力学理论出发，提出了一种适用于计算挟沙水流等涉固流动问题的两相流湍流模式，着重探讨了受排沙底孔影响的区域内的水沙运动特性。 文中分析和总结了以往研究悬移质颗粒扩散系数的理论和方法，指出了其中存在的困难，并基于两相流理论和随机理论，首次提出了关于悬移质颗粒扩散系数的投影寻踪数学模型，预测结果与实验数据吻合较好。用本文所提出的水沙两相流湍流模式，从理论上分析了近壁区内水沙运动特性和湍流悬浮机理，建议采用考虑压力梯度的壁面函数处理近壁区流速分布。分析和总结了现有理论和方法在研究挟沙水流运动规律中的不足和困难，认为本文的研究方法较基于泥沙运动力学和两相流理论的研究方法更具合理性和优越性。首次提出相间滑移速度是由相间对流速度和相间漂移速度所组成的新观点，理论上为深入研究挟沙水流运动规律提供了某种可能性。通过数值模拟和理论分析说明了相间漂移速度在靠近床面的区域内相对较为显著，这对于泥沙的湍流悬浮和输移扩散有较大的影响。通过与其他多相流模型的比较，提出了相间时均速度差是造成滑移的主要原因而湍流扩散漂移对滑移的影响较小的观点。 运用本文所提出的水沙两相流湍流模式，对前人已做过的挟沙水流精确实验的某些工况进行了数值模拟和验证，计算结果与实验结果吻合良好。对具有强三维运动的排沙底孔前受孔口影响域内水、沙运动特性和冲刷漏斗形态进行 四川大学博士学位论文了数值模拟和理论分析，结果表明，在孔口影响域内含沙量及其浓度梯度在水深方向上均呈现出上小下大的规律，尤其在靠近床面的区域内，含沙浓度梯度很大。含沙量在孔口影响域内的这种分布规律对该区域内挟沙水流流速分布将产生一定的影响。 本文研究结果还表明，在距排沙底孔较远的孔口影响域以外的区域，挟沙水流流速在水深方向上成对数或指数分布；而在孔口影响域内，挟沙水流流速分布不同于单相水流的对数或指数流速分布规律。在孔口影响域内，水沙两相不仅在垂向上有速度滑移，而且在水平方向上也有相对运动。因此现有泥沙数学模型中只考虑泥沙颗粒的垂向沉降而忽略其它方向上相间滑移的处理，只适合于紊流充分发展的水沙两相流情况。另外，在紊动极强的冲刷漏斗区内，泥沙沉速小于静水中沉速，完全不考虑泥沙沉速的时空变化、甚至用静水中泥沙颗粒的沉降速度代替动水中的沉速均不符合实际情况。本文所提出的水沙两相流湍流模式，对上述两方面较现有的研究方法均得到了较好地解决。 基于工程泥沙的分析方法，从排沙底孔前冲刷地形数值模拟的结果可以看出，局部冲刷漏斗的形态与泄水孔口的布置型式、位置以及水库的运用方式有密切的关系。越靠近泄水孔口，冲刷漏斗区内下切侵蚀和横向侵蚀越强烈。排沙底孔前冲刷漏斗在水沙两相相互作用下所形成的平衡形态，是一种动平衡形态。 本文所提出的水沙两相流湍流模式和关于悬移质颗粒扩散系数的投影寻踪数学模型，进一步丰富和完善了挟沙水流运动规律的理论框架，为解决含沙水流等涉固多相流问题的研究提供了新的思路和途径。更多还原

【Abstract】 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更多还原