A Novel Improved Coupled Dynamic Solid Boundary Treatment for 2D Fluid Sloshing Simulation

In order to achieve stable and accurate sloshing simulations with complex geometries using Smoothed Particle Hydrodynamic (SPH) method, a novel improved coupled dynamic solid boundary treatment (SBT) is proposed in this study. Comparing with the previous SBT algorithms, the new SBT algorithm not only can reduce numerical dissipation, but also can greatly improve the ability to prevent fluid particles penetration and to expand the application to model unidirectional deformable boundary. Besides the new SBT algorithm, a number of modified algorithms for correcting density field and position shifting are applied to the new SPH scheme for improving numerical stability and minimizing numerical dissipation in sloshing simulations. Numerical results for three sloshing cases in tanks with different geometries are investigated in this study. In the analysis of the wave elevation and the pressure on the tank, the SPH simulation with the new SBT algorithm shows a good agreement with the experiment and the simulations using the commercial code STAR-CCM+. Especially, the sloshing case in the tank with deformable bottom demonstrates the robustness of the new boundary method.

A Study of Wall Temperature Jump Using UGKS Simulation With Diffuse-Specular Maxwell-Type Boundary

As the Maxwell-type boundary treatment can automatically capture temperature jump on boundary, it is widely used in gas flow simulation like Lattice Boltzmann method and Direct simulation Monte Carlo method. In present study, diffuse-specular Maxwell-type boundary with a diffusive fraction (a), which decides the mechanism of interaction between gas molecules and boundary, is realized in UGKS simulation. This diffuse-specular boundary can recover diffuse Maxwell boundary when a = 1.0, which proves the reliability of present boundary treatment. The influence of diffusive fraction on wall temperature jump under Knudsen number ranging from 0.001 to 1.0 is tested. The test cases are steady and unsteady state conditions of heat conduction and Couette flow between two infinite plates setting at specified temperatures. It is found that: 1) for cases of Knudsen number ranging from 0.01 to 1.0, owing to the loss of influence from equilibrium part on evolution of boundary gas distribution, the relative temperature jump increases when diffusive fraction varies from 1.0 to 0.25, this phenomenon is especially obvious on extreme point part in unsteady state cases; 2) for cases of Knudsen number equaling to 0.001, diffusive fraction has no significance influence on temperature jump as the temperature jump is less noticeable for such condition. Present study will help the further researches of heat transfer in rarefied gas.