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 1000

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.