Meshfree modeling of a fluid-particle two-phase flow with an improved SPH method

摘要

Fluid-particle two-phase flows are very complex and quite challenging to numerically simulate due to the complex and constantly moving fluid-particle interface. Recent developments in meshfree and particle methods provide alternatives in modeling fluid flows with moving boundaries. In this paper, a modified smoothed particle hydrodynamics (SPH) method is developed to simulate particle sedimentation (two-dimensional) in Newtonian fluids. The modified SPH includes an enhanced particle approximation scheme, an effective solid boundary treatment algorithm, the artificial stress model, and a turbulence model. By decoupling a field variable and its derivatives in a finite particle method, a decoupled finite particle method is presented, which balances accuracy, efficiency, and stability in SPH simulations without the necessity of solving redundant and challenging corrective matrix equations. A coupled dynamic solid boundary treatment is developed to improve the accuracy near the fixed and moving solid boundaries. The artificial stress term is added into the SPH equations of motion to remove the possible tensile instability phenomenon. The large eddy simulation model is incorporated into the SPH to describe the turbulence effects at high Reynolds numbers. Four different particle sedimentation tests are conducted using the modified SPH along with the finite element fictitious boundary method. It is demonstrated that the improved SPH method can achieve much better results than the conventional SPH while showing a good comparison with the results from the finite element fictitious boundary method and from other sources.