Application And Research Of Numerical Simulation Of Moving Interface On Stratified Flows Problem

Stratified flows are often induced by single component (e.g. temperature, active scalars) or multi-components in natural water body. Multi-components caused complicated flow characteristics of stratified flows due to the difference of their own diffusion and component's contribution to water density. In the paper, the Level Set Method is applied to track the moving interface between two fluids and every phase is calculated respectively combined the interface effects. Finally, Sewage outfall problem is simulated by 2D and 3D system based the paper, and the process and mechanism of the saline intrusion is explained. The main works of the paper include as follows:(1) To track the moving interface,the Level Set Method is applied in the paper. Under the unstructured grids system, the method is studed and established based the idea of Fast Marching Method and Source Point Scanning Method, and then the Level Set Method is compared with the VOF Method based a given example.(2) On the paremeters of the cell near the interface between the two fluids, such as the density and diffusion coefficient, etc. in the paper, two different methods is studied. To the 2D problem, the volume of phase fluids can be calculated from sign distance function,and then the paremeters can be acquired also; To the 3D problem, the paremeters are dealed smothly using sinusoid. Finally ,the method of isobaric fix ghost is applied to extend the variable of the cell near the interface.(3) In the paper, the density-equation and momentum-equation are unified as a integral style by transforming the momentum-equation, and then the equations are dispersed under unstructured grids with the use of reconstruction of grads and superbee limiter. SIMPLE(SIMPLEC) Method and Artificiale Compressibility Method are improved to solve the pressure-velocity coupling . The problem of outlet boundary is studied in the paper, and some technique are put forward to deal the free boundary. Finally , some example are given to test the technique.(4) In the paper, the standard k-εturbulence model is established with Wall Functions dealing the flow near walls.(5) Finally, Sewage outfall problem is simulated by 2D and 3D system based the paper, and the process and mechanism of the saline intrusion is explained.