【作者】 黄细彬；

【导师】 金忠青；

【作者基本信息】 河海大学 ， 水力学及河流动力学， 2001， 博士

【摘要】 本文针对高速含沙掺气水流的运动规律有别于低速水流及清水单相流，在自己研制的高速浑水循环系统中，通过对高速含沙掺气水流壁面剪切应力和脉动压强等参数的量测，分析了水沙气三相流的紊动特性，探索了泥沙对固壁的磨蚀机理及减蚀措施，其主要内容包括以下几个方面：1．对紊动水流、含沙水流、水气两相流及泥沙磨蚀的研究状况进行了综述，提 出了本文的研究对象和拟采取的技术路线。2．建立了多相流压强脉动基本方程，阐述了水流脉动压强基本理论，分析了压 强脉动机理；根据试验数据，探讨了水、气、沙三相流体的压强脉动特性， 初步得到了高速含沙掺气水流脉动压强的幅值特性与频域特性；提出了脉动 压强强度系数、脉动压强极差系数与含沙量、掺气浓度的关系。3．简要地介绍了分维的定义和计算，运用相空间重构法对含沙掺气水流脉动压 强信号进行处理，计算了浑水、清水、掺气三种不同水流状况的关联维数。 结果表明，不同水流状况具有不同的关联维数，含沙掺气水流运动并非完全 随机的，而是具有内在有序性。计算得出的不同关联维数反映出不同脉动压 强信号序列所具有的不同分形特征，说明动力形成机制、系统复杂程度的差 异。4．用自行研制的剪切力传感器分别量测了清水、掺气水流及挟沙水流壁面上的 剪切力；基于实测资料，分析了壁画剪切应力的时均值和脉动值与水流速度 的关系、掺气与摩阻系数的关系；研究了掺气及含沙量对固壁剪切力的影响； 提出了掺气有助于减小水流对固壁边界的摩擦阻力；在同一流速下，剪切力 的时均值及脉动值随着含沙量的增加而略有增加，随着掺气浓度的增加而降 低。5．分析了空蚀与磨蚀的不同物理特征；探讨了沙粒磨蚀机理，提出了影响磨蚀VI 河海大学博士学位论文一 的因素；研究了掺气抗磨的可能性：建立了混凝土材料壁面磨蚀率的计算公 式；说明含沙水流对固壁材料的磨蚀率随掺气浓度、材料强度的增大而减小， 随水流流速、含沙量的提高而增大；利用掺气可有效地降低过流表面的泥沙 磨蚀率。6．应用了k－。紊流模型计算了强迫掺气设施后的水气两相流，计算结果与实测 值的比较表明，所采用的预测方法是行之有效的。更多还原

【Abstract】 The turbulent characteristics of high-velocity sediment-laden and aerated flow are more other than the clear water flow of single-phase and current of low speed. In a special circulating system with high velocity flow, some flow parameters such as boundary shear stress and pulsation pressure are measured. An investigation is made on the turbulent characteristics of the three-phase flow of water, air and sand. The mechanism of silt abrasion is studied. Specific contents are summarized as following:1. The research results of turbulent flow, sediment-laden, aerated flow and silt abrasion are introduced. The problems to be studied and the methods to be employed in this paper have been presented.2. The fundamental theory and equations for the pressure fluctuation are described and the wall pressure fluctuation is measured. Based on the experiment data, the characteristics of pressure fluctuations are analyzed in the three-phase flow of water, air and sand. The effects of air concentration and sediment content on the amplitude and frequency of pressure fluctuations are discussed.3. The definition and calculation of fractional dimension is introduced briefly. The pressure fluctuation signals are processed by reconstructing the phase space for sediment-laden and aerated flow. The correlation dimensions are calculated for sediment-laden flow, clear water and aerated flow. The results show that the correlation dimensions are different in different current conditions. It is indicated that sediment-laden and aerated flows are not completely stochastic, possessing its intrinsic order. Different correlation dimensions explain the differences of the dynamical mechanism and systematic complex level. Different pressure fluctuation signal sequences have different fractal characteristics.4. With the self-manufactured transducers, boundary stresses in clear water flow, aerated flow and sediment-laden flow are measured. Based on the experimental data, the relationship between shear stress and flow velocity, and the relationship between friction coefficient and air content are analyzed. The effect of air and sediment laden content on boundary shear stress is discussed. It is indicated that the higher the air concentration and the less sediment laden, the less the shear stresses.5. The surface material is liable to erosion wear with high- velocity sediment-laden flow, hi this paper, sand wear mechanisms are discussed and some effects of significant flow factors on material wear are analyzed; The possibility of preventing erosion wear with aeration is proposed; Based on test data, the formula for calculating the concrete material wall surface wear rate is derived. It is indicated that the wear rate is related to the air concentration, the strength of material, the flow velocity and the sediment content. It is shown that wear rate can be reduced with the help of flow aeration.6. Applying the k - e turbulence model, the distributions of air concentration are predicted for the air-water flow below an aerator. The validity of the numerical solution is demonstrated by the comparison between value measured and calculated.更多还原