水库高含沙异重流演化过程的动力学机制关键问题研究

High-content density current occurs in reservoirs on sediment-laden river when high-content flood comes. If the reservoir scheduling is not properly regulated, high-content density current stops and large deposition occurs, with reservoir capacity loss, and the full play of the reservoir comprehensive benefits affected. The previous research on ordinary turbid density current focused on plunging conditions and movement law and sediment flushing process, but research on theory and method of description on high-content density current plunging conditions, the Stranded layer after high-content density current and muddy pond variation process and its interaction mechanism with density current hasn't been studied much. Therefore, this project intends to adopt method combination of theoretical analysis, flume experiment and the surveyed data analysis, exposing the law on high-content density current vertical velocity distribution at plunging point, secondly plunging condition and movement mechanism on mid-layer density current nose especially under the background of muddy pond, complex process of evolution and dynamic mechanism between subsequent density current and muddy pond. Results will be proposed: theoretical formula which fits for high-content density current about plunging and secondly plunging into muddy pond, head velocity of mid-layer density current and hydraulic and dynamic parameters for description of its interaction between subsequent density current and muddy pond. This result will gain progress and breakthrough. The research has not only great important academic significance, but also can be directly applied to the reservoir scheduling with great practical value.

多沙河流水库遭遇高含沙洪水，往往形成高含沙异重流，若调度不当将产生大量淤积而损失库容，甚至影响水库综合效益的正常发挥。以往针对异重流的研究大多侧重于一般含沙异重流的形成条件、输移规律、排沙过程等，而针对高含沙异重流潜入条件的理论描述、高含沙异重流过后的滞留层和浑水水库的变化过程及其与后续异重流之间的作用机制等方面还鲜有研究。因此，本项目拟采用理论探讨、水槽试验和实测资料分析相结合的手段，揭示高含沙异重流潜入点垂线流速分布规律、浑水水库背景下后续异重流二次潜入条件与中层异重流头部运动机制、后续异重流与前期浑水水库之间的复杂演化过程和动力学机制。提出适用于高含沙异重流潜入和二次潜入浑水体的理论公式、中层异重流头部运动公式、描述后续异重流与前期浑水水库二者相互作用的水动力参量。本项目研究将在高含沙异重流运动理论方面取得进展与突破，具有较大的学术意义，而且可直接应用于水库调度，具有重要的实用价值。

多沙河流上往往发生高含沙洪水，水库处于蓄水状态，入库后便产生高含沙异重流。当入库洪水过程结束后，异重流因无后续驱动能量会停止运行而滞留库底，称之为滞留层，或异重流运行至坝前不能及时排出而形成浑水水库。本研究主要围绕水库高含沙异重流演化过程的动力学机制研究中涉及的关键科学问题，采用理论分析、数值计算、水槽试验等研究手段，主要得到以下结论：.（1）研究了复杂条件下高含沙异重流潜入动力学机制，提出了适用于高含沙异重流的潜入点水深公式，其计算值与实测值较为接近。.（2）通过异重流二次潜入以及中层异重流水槽试验研究了二次潜入及中层异重流演化机制，异重流二次潜入点处断面垂线流速分布基本服从二次抛物线分布，二次潜入点密度弗劳德数大小为0.09~0.10，相比一次潜入密度弗劳德数大大减小。提出了异重流二次潜入点公式，并提出了基于能量守恒的中层高含沙异重流头部流速公式。.（3）通过高含沙异重流与浑水水库作用的水槽试验，分析泥沙沉降与流变特性，揭示了极限切应力与水流切应力作用机理，提出了描述浮泥体可动性的水动力参量及临界厚度计算公式。当I>1时 ，“浮泥”层可发生流动。当I<1时, “浮泥”层不能流动。当I=1时，“浮泥”层处于临界状态，对应的浮泥层厚度为临界厚度。.以上研究成果既可为水沙数值模拟提供物理参数，丰富泥沙学科内容，又可为水库高效排沙、提高水库拦沙期使用寿命、优化水库调度，为水库正常发挥综合效益提供决策支撑，为滩区治理，缓解二级悬河问题提供技术支持，具有重要的过程价值和生产时间意义。