低速下水滴撞击固体表面运动模拟

Simulation of droplets impacting on solid surface at low velocity

以水滴撞击飞机部件造成结冰问题为背景,运用level set界面追踪方法,把不可压黏性方程组中的表面张力用level set函数表示,并利用2阶变密度投影算法求解二维不可压Navier-Stokes方程组,数值模拟了低速下的水气界面追踪问题.为了能够处理密度比为1 000的水气界面问题,在界面处引入了一定宽度的光滑过渡带宽,进而消除了由于界面两边大密度比引起的数值震荡,由此较为成功地模拟了大水滴在不同表面张力时撞击平板后的形态变化及其运动轨迹.数值实验结果表明本算法可以有效地处理界面处密度比和黏性很大的不可压多相流问题.考虑界面处的表面张力,本算法可模拟不同表面张力下的界面运动变化.

In the background of icing problem caused by the droplets which impacted on the surface of aircraft,the level set interface tracking method was used,the surface tension in the incompressible N-S equations was denoted by the level set function and the second-order projection method for variable-density flows was used to solve 2-D incompressible Navier-Stokes equations;the water and gas multiphase problems at low velocity were simulated.In order to simulate the water and gas multiphase problems of the density ratio up to 1 000,the numerical oscillations caused by the large density ratio between the interface can be eliminated by smoothing the density at the interface within a few grids.So the topological changes and movements of large droplets,which are different in surface tension when impacting on the solid interface,can be successfully simulated.The numerical results show that the method can be used to model the incompressible multi-phase flow with large density and viscosity density.Considering the surface tension,the movements of the surface at different surface tensions can be simulated.