泥沙异重流在层结盐水中运移、掺混及演变特性研究

Turbidity currents are important phenomena often existed in nature and practical engineering. The behaviors of the single-phase gravity current have been extensively studied, however the propagation of turbidity current in the stratified salt water, its mixing with salt water, and its transition are still lack of understanding, although it is of importance to seafloor morphodynamics, pollutant transport and deposition, and deepsea petroleum and gas shale formation, and seafloor communication cables, etc. Therefore, this project is going to study the turbidity current propagates in the stratified salt water and its interaction with the surrounding salt water under different stratifications, slopes, diameters and densities of sediment, etc. By conducting a series of flume experiments, this project will examine the Kelvin-Helmholtz instability at the interface of the turbidity current and stratified water and its impacts on the propagation and transition of turbidity current; to analyze the factors that influence the mixing between the turbidity current and salt water, the density changes of the turbidity and salt water, and the transport of sediments; to discuss the split of hyperpycnal flow, the development of mesopycnal flow, and the mechanism of these processes. Meanwhile, a high-resolution numerical model will be developed to simulate this highly dynamic process involving the turbidity current and the stratified salt water. By applying the numerical model and theory developed in the project, it should provide useful information to further understand turbidity currents and sediment transport in marine system, to explain the related phenomena in seafloor morphology, and to protect seafloor equipments and instrumentations and submarine cables in ocean engineering.

泥沙异重流是自然界和工程中广为存在的重要现象，但目前对于其在层结盐水中运动、与盐水掺混并发生流态演变的研究相对较少。本项目将开展一系列不同条件下的水槽实验、结合理论分析和数值模拟，研究不同层结度、底床坡度、泥沙粒径与浓度等条件下，泥沙异重流演进及其与层结水体相互作用的动力过程，重点研究不同因素下泥沙异重流与层结水体之间界面Kelvin-Helmholtz不稳定性的触发条件与影响因素，进而分析该不稳定性对异重流运动和演变的作用机理，分析异重流与层结水体掺混而导致水体交换和泥沙悬浮与输移的作用机制、探明异重流分离及中层异重流（侵入流）产生与发展的控制机理与临界控制条件；并研究能模拟该过程中异重流泥沙与层结水体相互作用、掺混和交换、及流态演变的精细化数值模型，从而结合机理分析和数值模拟，加深对不同水体环境中异重流运动过程的认识，为海洋地貌演变、海底油气开发、海洋工程与海底管线安全提供科学参考依据

泥沙异重流是自然界和工程中广为存在的重要现象，但目前对于其在层结盐水中运动、与盐水掺混并发生流态演变机制的认识相对不足。本项目开展了一系列不同条件下的水槽实验、结合理论分析和数值模拟，研究了不同层结度、底床坡度、泥沙粒径与浓度等条件下，泥沙异重流演进及其与层结水体相互作用的动力过程，重点研究了不同因素下泥沙异重流与层结水体之间界面Kelvin-Helmholtz不稳定性的触发条件与影响因素，阐明了该不稳定性对异重流运动和演变的作用机理，揭示了异重流与层结水体掺混而导致水体交换和泥沙悬浮与输移的作用机制，探明了异重流分离及中层异重流（侵入流）产生与发展的控制机理与临界控制条件；建立了能模拟该过程中异重流泥沙与层结水体相互作用、掺混和交换、及流态演变的精细化数值模型，提出了解释浊流长距离输移原因的新机理，加深了对不同水体环境中异重流运动过程的认识，为海洋地貌演变、海底油气开发、海洋工程与海底管线安全提供了科学参考依据。