【作者】 黄涛；

【导师】 白玉川；

【作者基本信息】 天津大学 ， 港口、海岸及近海工程， 2009， 博士

【摘要】 泥沙运动与水流的紊动现象密切相关,振荡流边界层存在于海底床面,虽然厚度相对水深而言很小,但其水流紊动特性与波浪的传播和变形、泥沙起动和输运、以及床面形态的变化密切相关,对其特性的研究具有重要的理论和工程意义。本文在前人工作的基础上,对振荡流边界层的数值研究引入大涡模拟方法,要通过数值模拟来反映振荡流和底泥的相互作用,引入大涡模拟湍流模型和底泥底部本构方程来建立波浪、水流和底泥相互作用理论模型。海岸泥沙主要受两种动力因素作用,即波浪和潮流的作用。但因潮流属于长周期波,其对底床泥沙运动,可利用河流泥沙运动规律近似描述。而波浪水流与单向水流不同,它存在着流速和压力的周期性振荡。对于振荡流在平床及沙纹床面上振荡流的湍流结构,且由于振荡流具有强剪切作用及各项异性,故而本文采用了有限差分法的各向异性的湍流数学模型,并取得了计算结果。通过与已有的前人实验结果对比,证明该模型在湍流能量、耗散以及雷诺应力都得到了较好的结果。通过对模型的改进,沙纹床面上的粘性涡结构也得到了很好的模拟,其流场状态,粘性涡的形成、扩散、“喷射”和破碎也得到了较好的体现。另外通过对海河口等地河口底泥的流变实验,本文对海河口几个典型泥场的淤泥流变特性及其材料特性进行了实验研究,并给出了相应的剪切力与剪切应变的曲线。更多还原

【Abstract】 The turbulent bottom layer induced by the wave or wave combined current over rough bed has been received much attention from coastal engineer. Although the thickness of this bottom layer is quite small compared with the water depth, it still play a very important role in determining the sediment suspension and movement, the rate of wave energy dissipation, and the magnitude of bottom shear stress. Therefore, a numerical model is developed to describe the essential feature in the oscillatory bottom layer, and the large eddy simulation technique is used to model the sub-grid scale turbulence effects, the correspondence between the measurement and the simulations seems to be good in all case.When we discuss the interaction between the wave and sediments, the turbulence must be concerned. This paper mainly considers the oscillatory bottom boundary layers over flat or rippled sea beds. Owing to the strong shear and anisotropy of oscillatory flow, an anisotropic turbulence mathematical model is set up using the finite difference method, and the computational results of the model are verified by comparisons with well known experiments. Turbulent energy, dissipation and Reynolds stress can all be computed with this mathematical model, and the development processes of a large coherent vortex structure over a rippled bed, such as main flow separation, coherent vortex formation and curling, coherent vortex ejection and breaking up are successfully simulated.In addition, this paper discussed the turbulence characteristic of oscillatory bottom layer over plane rough bed in detail. It need to study the coherent structure closed the bed and build the new wall boundary condition for mud.更多还原