溃坝波数值模拟及其在坡面水流问题中的应用

Numerical Simulation of Dam-break Flow and Its Application in Overland Flow

为探讨不同方法模拟溃坝波的适用性和准确度,采用基于Roe格式的近似黎曼解方法与追踪自由表面的VOF方法模拟了二维对称矩形溃坝模型。结果表明,两种方法均能较好地模拟出溃坝波的传播过程,但与实测值的对比分析发现,采用Roe格式模拟的结果与实测值拟合较好,VOF方法对网格尺寸的要求较Roe格式更加精细。由此,基于既考虑降雨强度的变化,又考虑降雨动量和风的影响的缓坡和陡坡都适用的坡面径流基本方程,构建了基于Roe格式的坡面水流水动力模型,模拟了自然降雨条件下的坡面流运动情况,并通过相应的模型试验进行对比验证。模拟流速与实测流速之间拟合度较好,表明模型具备了模拟大坡度、浅水(深水)流的能力,为坡面流的水动力学机制研究提供了参考。

In order to study the adaptation and accuracy of the numerical simulation methods for dam-break flow, the Roe Riemann Solver and free surface tracing method of Volume of Fluid (VOF) model were applied to simulate the 2D symmetric rectangular dam-break flow. The results demonstrate that these two methods are both able to simulate the dam-break flood wave propagations. Through the comparative analysis with the measured values, it is found that the simulated results with Roe scheme are better fitted to the measured values and the mesh size of VOF method is required to be more fine than Roe scheme. Therefore, based on the governing equations of overland flow, which are applicable to both gentle and steep slopes, and considering the rainfall intensity and the influence of rainfall momentum and wind, a Roe scheme computing model is developed for rainfall-runoff over steep slopes. The simulation of overland flow was performed under natural rainfall conditions,and the model test was correspondingly carried out for comparison and verification. The agreements between the simulated and the measured velocity values indicate that the model is capable of simulating the overland flow of steep gradients and shallow water depth, which can be useful for relevant research of overland flow over steep slopes.