基于浸没边界法的流固耦合模拟分析

Fluid-solid Coupling Simulation Analysis Based on Immersed Boundary Method

钠冷快堆(Sodium-cooled Fast Reactor,SFR)作为第四代反应堆系统的重要堆型之一,采用非能动停堆组件保证安全性已成为国内外研究共识。然而,在对非能动停堆组件落棒停堆过程进行模拟时,由于复杂几何、存在孔隙结构以及运动边界等问题的存在,传统计算流体力学(Computational fluid dynamics,CFD)程序所使用的结构化网格或非结构化网格生成方法在解决该类问题时存在较大的局限性。本文基于浸没边界法开发了相应的求解程序,该法无需构建复杂的贴体网格,而是采用简单的笛卡尔网格,通过将体积力添加到控制方程中的方式纳入边界条件,适合上述工况的模拟过程。并对程序的准确性进行验证分析,分别模拟了在二维固定圆柱绕流下的稳态流动、不稳定流动,以及二维振荡圆柱不稳定流动,得到涡旋特征参数、阻力系数、升力系数、斯特劳哈尔数,以及涡脱落情况等数值模拟结果,并将其与已有文献数据进行对比,结果显示本求解器具有良好的效率和准确性。

Sodium-cooled fast reactor(SFR)that is one of the important types of the fourth-generation reactors has adopted passive shutdown assembly to ensure system safety.However,due to the existence of complex geometries,hole structures and moving boundaries,traditional CFD codes using body-fitted grids often encounter problems when dealing with the process of simulating the shutdown process of the passive shutdown assembly,even with unstructured grids.Therefore,it is necessary to develop powerful and versatile numerical simulation tools and adopt accurate and effective numerical methods to simulate these actual complex engineering conditions.This work develops a corresponding solution program based on the immersed boundary method,which does not need to construct a complex body-fitted grid and uses a simple Cartesian grid.The boundary conditions are represented by the addition of an ad-hoc body force in the momentum equations.The effect of classical no-slip boundary conditions at the physical surface of the immersed body is represented by the body force.Furthermore,various 2D well-documented test cases of academic flows around fixed or moving cylinder have been simulated and carefully validated with existing data from the literature.Simulation results include vortex characteristic parameters,drag coefficients,lift coefficients,Strouhal number,and vortex shedding constitutions.The results compared with literature showed this code has good efficiency and accuracy.