基于SPH法对明渠非均匀流内悬移质运动的多尺度特性研究

Formal researches on sediment suspension in non-uniform flow have mostly emphasized on the exploration of the space-time averaged law of the motion. Those research outputs can provide large-scale information in the solution of scientific and engineering problems, but they can't provide the detail information in smaller scales that is necessary to handle the aquatic and sediment related emergencies which increasing rapidly in China. The boundary conditions of non-uniform sediment-laden open-channel flow are relatively regular,so this project takes open-channel flow as research object. By adopting Smoothed Particle Hydrodynamics (SPH) into the study, the research is aimed at carrying out basic scientific research to reveal the multi-scale motion characteristics of suspended load in non-uniform open-channel flow..The research will focus on four aspects: .(1) To clarify the sorts and the mechanisms of the forces which are exerted on the suspended sediment particle in non-uniform flow based on particle dynamics..(2) Digestion of SPH theory, theoretical illustration of multi-scale physical pictures of suspended load motion from the SPH perspective. .(3) Develop the "Suspended load motion SPH model", carry out flume experiment and corresponding numerical simulation. Calibrate and validate the SPH model by experiment results..(4) Simulation of non-uniform sediment-laden open-channel flow, reveal the multi-scale motion characteristics of suspended load in it..The study on multi-scale motion characteristics of suspended load in non-uniform open-channel flow will promote the development of sediment research subject, provide scientific evidences for handling the aquatic and sediment related emergencies, and the research is dedicate to lay the theoretical and technical foundation for the study on motion characteristics of suspended load in natural non-uniform flow whose boundary conditions are more complicated, it is of great scientific significance and possesses a good application prospect.

以往对非均匀水流内泥沙悬移运动的研究多侧重探索时空平均规律，以之解决科研和工程问题时可提供大尺度信息,但在应对当前我国高发的涉水涉沙突发问题时无力提供中小尺度的细节信息。本项目以边界条件相对规则的明渠非均匀挟沙水流为研究对象，基于无网格光滑粒子流体动力学(SPH)法，对明渠非均匀流中悬移质运动的多尺度特性开展基础科学研究，具体内容包括：1.明确非均匀水流中悬沙颗粒受力种类及各力作用机制；2.解析SPH理论，建立悬移质运动的多尺度SPH物理图景；3.构建"悬移质运动SPH模型"，开展非均匀挟沙水流水槽试验和相应的数值计算，利用试验结果率定并验证SPH模型；4.模拟明渠非均匀挟沙水流，揭示其内悬移质运动的多尺度特性。通过本项目的研究，可促进泥沙研究学科发展，为应对涉水涉沙突发事件提供科学依据，并为研究具有复杂边界的天然非均匀流内的悬移质运动特性奠定理论和技术基础，极具科学意义和应用前景。

本项目的研究重点主要有两方面，一是无网格光滑粒子流体动力学(SPH)法在水沙运动数值模拟领域的应用，二是对不同尺度悬移质运动特性及其计算方法的研究。.对于第一方面工作，本研究完成了对经典有网格法和SPH法理论的总结，阐明了SPH法数值离散原理，推导了水流运动方程SPH离散形式，采用以给粒子直接赋予固体属性的方式模拟悬移质颗粒。介绍了C++11.0引入的并行机制，提出了C++加速大规模并行计算技术（Accelerated Massively Parallel）和并行模式库（Parallel Patterns Library, PPL）等新技术和新工具在水沙模拟软件中的应用方案，编制了SPH水沙运动模型软件，开展了基于SPH法的数值试验。. 对于第二方面工作，对于小尺度的水沙运动，本研究完成了对非均匀水流中悬沙颗粒受力情况的总结，开展了非均匀挟沙水流水槽试验，描述了悬移质运动特性。对于大尺度范围内的悬移质运动，提出了通过有向图构建河网关联矩阵并以之求解一维天然河网恒定流的新方法，与传统的河网三级解法不同，此方法所构建的方程组的系数矩阵是对称正定稀疏矩阵，可采用共轭梯度法（Conjugate Gradient, CG）快速求解，与一维泥沙运动方程相结合，可求解天然河网恒定流内的水流和悬移质输移过程。. 本项目的研究成果，为计算不同尺度水流和悬移质运动探索了新途径，研发了新工具，提出了新算法，不仅可促进水沙学科发展，而且具有广阔的应用前景。

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