非均匀加糙床面复杂精细结构的分形量化及其致阻机理研究

River model test is an important means to solve complex engineering problems of flow and sediment, and roughness resistance theory is the theoretical basis of model experiment study. In river model test, inhomogeneous roughness is often used due to the spatial variation of river bed morphology, but the calculation of inhomogeneous roughness resistance still mainly relies on empirical methods for uniform roughness resistance. However, these empirical methods only consider the contribution of the representative particle roughness, they can not reflect the synergistic effect of overall bed particles, also failed to reveal the interaction of flow and rough beds with complex fine structure, which lead to difficulties in accurate determination of inhomogeneous roughness resistance and the need to adjust bed roughness repeatedly, and then affect the fine simulation of river..Therefore, based on the application of multidisciplinary knowledges, by using the methods of flume experiments combined with theoretical analysis, this project aims at studing on the fractal characteristics and quantitative method of inhomogeneous rough beds with complex fine structure, together with investigating the effect laws of fractal characteristics of bed surface roughness on the flow structure and the roughness resistance. Through the investigation of these fundamental issues, an integrated fractal description model for rough beds will be built, the fractal mechanics mechanism of roughness resistance will be revealed, and the fractal calculation method for roughness resistance will be proposed. The research results of this project not only have an important theoretical significance in aspects of establishing the quantitative expression of fractal mathematics for complex fine structure and expounding flow resistance mechanism of complex boundary, but also have an great practical value in hydraulic engineering and water transport engineering practice.

河工模型试验是解决复杂工程水流泥沙问题的重要手段，加糙阻力问题是模型试验研究的理论基础。受底床形态空间变异影响，河工模型试验常采用非均匀加糙方式，但其加糙阻力计算却仍主要依靠均匀加糙阻力的经验方法，该方法仅考虑代表颗粒对加糙的贡献，难以体现颗粒总体的协同作用效应，未能反映床面复杂精细结构与水流的相互作用，导致非均匀加糙阻力至今尚难准确确定而需反复试糙，影响河流精细模拟。.为此，本项目拟在多学科综合交叉的基础上，采用水槽试验和理论分析相结合的方法，研究非均匀加糙床面复杂精细结构的分形特征及量化方法，探讨加糙床面分形特征对水流结构和加糙阻力的影响规律，建立加糙床面综合粗糙形态结构的分形量化模型，揭示加糙阻力形成的分形力学机理，提出加糙阻力的分形计算方法。研究成果对建立复杂精细结构的定量分形数学表达、阐明复杂边界水流阻力的形成机理具有重要理论意义，同时在水利水运工程实践中具有重大实用价值。

河工模型试验是解决复杂工程水流泥沙问题的重要手段，加糙阻力问题是模型试验研究的理论基础。河工模型加糙阻力与床面颗粒总体的协同作用效应关系密切，并受床面复杂精细结构与水流相互作用的影响。本项目采用水槽试验和理论分析相结合的方法，研究了非均匀加糙床面的分形特征和统计粗糙特性，探讨了分形尺度区和覆盖基准面的确定方法，获得了分形维数随床面颗粒组成及高程统计参数的变化规律，分析了剖面轮廓及粗糙床面的高程变异特征。基于PIV水槽明渠紊流试验资料，研究了床面加糙对明渠紊流流速分布和紊动特性的定量影响规律，探讨了当量糙率尺度和水流阻力系数的沿程分布规律及其内在关系，分析了加糙床面分形特征与水流阻力的响应关系。在此基础上，建立了加糙床面综合粗糙形态的分形量化模型，揭示了加糙阻力的形成机理，提出了加糙阻力的分形计算方法。本项目研究成果对建立复杂精细结构的定量数学表达、阐明复杂边界水流阻力的形成机理具有科学意义，同时在水利水运工程实践中具有应用价值。