【作者】 杨学斌；

【导师】 李绍武；

【作者基本信息】 天津大学 ， 港口、海岸及近海工程， 2008， 硕士

【摘要】 淤泥质海岸泥沙的淤积问题一直是困绕港口、航道正常作业的关键问题。二维水流泥沙数学模型是计算航道和港内泥沙淤积量的有效方法,本文拟对此开展研究。主要研究工作概括如下。一、用COASTTOOL2D水流模型进行流场模拟,并对模型进行了改进。在数值模拟中发现,原COASTTOOL2D水流模型在底坡较大时通量计算会产生较大误差。其原因是在非线性通量计算中近似采用了单元边平均水深,本文通过积分导出了倾斜底坡下对流通量的补偿项,从而使模型可推广到地形变化较大的区域。二、在动边界处理中,新提出一种网格淹没度的概念,并据此导出一种控制方程新的离散方法,将半淹没网格视为渐变连续体处理,使边界处水量计算与动边界实际位置相吻合。应用此种方法可以将动边界单元与内单元统一处理,从而避免了动边界处因干湿单元变换引起的数值振荡。此方法的特点是在无须重新划分网格前提下达到可变网格的计算效果,理论上严谨,应用方便,计算准确且速度较快,在工程中有很强的实用性。三、新提出一种线单元处理方法,用于模拟水下强变化地形——潜堤。数值实验表明,潜堤淹没前后,流场可以平顺过度,增强了模型的适应性。四、在水流和泥沙模型中考虑波浪的影响,建立了波流共同作用下悬沙输运数学模型,运用该模型对天津港及其周围海区泥沙运动过程进行了模拟。更多还原

【Abstract】 Sediment siltation has always been a big problem that affects the normal operation of ports and channels on muddy coast. 2D sediment numerical model is an efficient method to calculate the sediment deposition in the harbor and channel. In this dissertation some research will be carried out on this topic and is outlined as follows.1. Numerical simulations will be performed by using the COASTTOOL2D flow model to study the flow field, and then the model will be improved by means of theoretical analysis and strict derivation. In the numerical tests of flow field it is found that the former version of the COASTTOOL2D flow model involves significant error in the calculation of numerical flux under the condition of a steep bottom slope. The reason for the error is that the average water depth on each side of the grid is adopted when calculating the nonlinear numerical flux. In this research, a compensation term for the convective flux, which is caused by the bottom slope of the element side, is derived by means of integration and is added to the discretized equation. In this way, the COASTTOOL2D flow model can be extended to the areas where topography varies violently.2. In the treatment of movable boundary, we put forward a new discretization method for the governing equations according to a newly proposed concept——submergence index. By this method, the semi-submerged elements can transit smoothly and continuously from a dry one to a completely wet one instead of an abrupt shift, which makes it is possible to adjust the water quantity exactly according to the location of the movable boundary and to implement a unified approach in dealing with the elements at movable boundary and inner grids. It is also possible that numerical oscillation caused by abrupt shift between wet and dry elements can be avoided. The advantages of the method are that not only can we obtain a higher computational efficiency of variable element without reconstruction of element system, it is also strict in theory, convenient for application, accurate in calculation and with a high processing speed. The improved COASTTOOL2D flow model can be widely used in practical engineering.3. In the thesis, a new concept of line element is proposed, on the basis of which, the model is improved for the application of flow over a violently varying underwater topography, e.g. a submerged dike. Numerical tests indicate the success of the model to be applicable to the case of submerged dike and thus the application range of the model is further extended.4. In the flow and sediment model we incorporate the effect of wave effect. And by using the model, tide flow and sediment movement inside and around Tianjin Port are simulated.更多还原