Large eddy simulation of pollutant movement in water

Abstract

本文采用大涡模拟方法封闭引入浮力特性并经空间平均后的Navier Stokes紊流方程 ,对水环境中污染物的运动规律进行研究。在用有限差分法对控制方程进行求解时 ,用破开算子法将控制方程分为对流、扩散和源项三部分 ,其中对流项用QUICKET程式求解 ,扩散项用中心差分求解 ,源项用Gauss Seidel迭代法求解。数值计算结合物理模型结果表明 ,污染物团在水环境中运动除有时均定量关系之外 ,还有三大定性规律 :第一 ,污染物团在时间和空间上具有不规则性 ;第二 ,污染物团后部是空的 ;第三 ,在同一条件下进行多次试验 (数学和物理 ) ,污染物团的运动是不一样的。计算表明大涡模拟要优于通常的κ -ε紊流模型 ,它不但能够象κ -ε紊流模型那样计算出污染物在水环境中的时均运动规律 ,而且能够计算出其在空间上的不对称发展过程 ,能够准确地再现其在物理模型中的不对称运动特性。计算结果无论从定性特性还是从定量关系上都与试验结果吻合一致 The large eddy simulation (LES) method is applied to the closure of N-S equations in the study of pollutant movement in water. The 3-D buoyancy extended large eddy model is established for numerical simulation. The governing equations are split into three parts during solving the finite difference equations for advection, dispersion and propagation. The advection part is solved by QUICKEST program. The dispersion part is solved by central difference method and the propagation part is solved implicitly by using the Gauss Seidel iteration method. The numerical simulation is in good agreement with experimental result. It is concluded that: 1)pollutant lump has an appearance of characteristic protuberances; 2) hollow is happened to the rear of the pollutant lump; 3) variability between different pollutant realizations may exist even if the events have the same parameters. The result shows that the LES method is better than the k ε model.