一种适用于模拟水力机械内部流动的水平集-浸入边界法研究

Level-set based immersed boundary method for simulating internal flows of hydraulic machinery

该文提出了一种适用于数值模拟复杂水力机械内部三维不可压缩流动的水平集-浸入边界法。采用有限差分法和投影法对流体域控制方程进行离散求解,时间推进采用二阶龙格-库塔格式。在浸入边界点上压力和速度进行强制重构,以满足相应的速度和压力边界条件,进而实现了考虑固体结构边界的三维流场数值模拟。基于非结构三角形网格离散固体区域的复杂边界,通过搜索圆计算流固交界面附近一定距离内网格点至交界面的距离和采用射线法区分流体域和固体域,实现了一种利用水平集函数准确且快速捕捉复杂流固交界面的方法。通过一系列标准测试算例验证了算法的精度与鲁棒性,并应用于轴流泵泵段的三维模拟。结果表明,该文基于水平集的浸入边界法可以有效模拟固体运动下的三维流场,并适用于水力机械三维复杂流动。

A novel level set based IB(immersed boundary)method is advanced to simulate incompressible internal flows with geometrically complex hydraulic machinery.The governing equations of the fluid field are discretized on a staggered Cartesian grid layout by using an accurate finite difference projection method.The discrete equations are integrated in time via a second order Runge-Kutta scheme.Both pressure and velocity fields of b oundary conditions are enforced through reconstructing them on IB nodes.Unstructured,triangular meshes are employed to discre tize complex immersed boundaries of arbitrary bodies,a search circle is utilized to calculate the distance between grid points and f luid-solid interface,a fast ray tracing method is used to classify fluid and solid computational domains,afterwards an accurate an d fast level-set based method for capturing complicated fluid-solid interface is developed.The accuracy and robustness of the code are validated with benchmark test cases and the code is applied to simulate the turbulence flow past a complex axial-flow pump.The results show that the level-set based immersed boundary method can be effectively used to simulate the three-dimension al flow field under solid motion and is suitable for the three-dimensional complex flow of hydraulic machinery.