颗粒形态和表面电荷分布对粘性泥沙絮凝-沉降-再悬浮过程影响研究

The flocculation-settling-resuspension process plays an important role in the concentration distribution of suspended sediment, the form of fluid mud Layer and the transport of cohesive sediment. However, many researchers didn't treat it as a dynamic process and studied one or two aspects within their own fields. Furthermore, they often ignored the effect of internal factors, such as particle shape and surface charge distribution of cohesive sediment, which are significant to understand this process. Thus, we will study the effects of particle shape and surface charge distribution on the flocculation-settling- resuspension process through laboratory experiment and numerical simulation. Based on floc fractal growth theory and cohesive sediment floc growth model, we will develop a model which can simulate the flocculation-settling- resuspension process of non-spherical charged cohesive particles, combining the experimental result of studying the regularities of particle shape, surface charge distribution and the resuspension pattern of primary settling sediment flocs. Then we will study the influence rule and mechanism of particle shape and surface charge distribution on this process and discuss each effect of flocculation, settling and resuspension on this process using the new model. The research findings not only enrich the theory of cohesive sediment movement, but also can provide an evidence for the planning and design of the projects in estuary area.

粘性泥沙絮凝、沉降和再悬浮过程对河口悬沙垂向分布、浮泥层的形成及泥沙输移等起着重要作用，而目前研究大多是从各自学科出发研究自己关心的某一或两方面，较少将其作为一个动态过程开展研究，且往往忽略泥沙颗粒形态和表面电荷分布这类内部因素的作用，而研究这类内部因素的影响对于深化理解这一过程具有重要意义。本项目拟采用室内试验和数值模拟方法围绕颗粒形态和表面电荷分布的影响展开研究，基于絮团分形生长理论和已有粘性泥沙絮团三维无网格生长模型，结合室内试验关于颗粒形态、表面电荷分布规律及初沉泥沙再悬浮模式的研究成果，构建非球体带电粘性泥沙絮凝-沉降-再悬浮动态过程三维数学模型，进而利用新建模型从微观角度揭示颗粒形态及表面电荷分布对粘性泥沙絮凝-沉降-再悬浮过程的影响规律和机理，并探讨絮凝、沉降及再悬浮在这一过程中的作用。研究成果将丰富粘性泥沙运动理论，为河口等地区的工程规划设计等提供依据。

本项目通过分析国内外有关粘性泥沙颗粒形态、絮凝、再悬浮文献和室内试验结果，构建和描述了粗糙带电数学泥沙颗粒，优化了粘性泥沙再悬浮量计算公式，并在此基础上，在微观层面和宏观层面分别建立了粗糙带电粘性泥沙絮团生长模型和考虑泥沙形貌的粘性泥沙絮凝-沉降-再悬浮运动过程数学模型，分析了泥沙粗糙表面和非均匀电荷分布对絮凝速率、絮团形态、粒径分布等的影响规律，研究了盐度和水流对粘性泥沙絮凝-沉降-再悬浮的影响规律，探讨了强紊动水体中絮凝、沉降和紊动扩散在这一动态过程中的作用。研究结果表明，粗糙带电粘性泥沙的絮凝速率较大，形成的絮团粒径分布范围较窄，且分型维数较大；电解质的存在将分别增强和减弱高、低强度水流所起作用，相同浓度下，当阳离子化合价从+1价变成＋3价时，水流的影响作用更明显，尤其体现在稳定段；粘性泥沙再悬浮模式和量与其存在状态、水流条件、分形维数等相关；强紊动水体中，上层区域泥沙絮团分布的决定因素是沉降和紊动扩散；中部区域是絮凝；下层区域是絮凝和紊动扩散。项目研究成果不仅丰富了丰富粘性泥沙运动理论，并能为河湖生态清淤、河口等地区的工程规划设计等提供依据，具有重要的科学意义与实际应用价值。