Parallel Numerical Simulation Of Liquid Sloshing And Multiphase Flow Problems Based On SPH Method

Liquid sloshing is common and significant for naval architecture and marine engineering.As the development of LNG,FPSO,the study of liquid sloshing is continuous.As a meshless lagrangian particle method,the Smoothed Particle Hydrodynamics(SPH)method has many obvious advantages in simulating sloshing problems:Firstly,free surface or multi-intersection interface can be directly distinguished by the physical properties of the particle,without any additional interface tracking and capturing algorithms.In addition,without constructing complex mesh,it is convenient for simulating large liquid deformation problems,such as wave propagating,wave rolling,wave breaking,wave splashing and wave slamming.However,the SPH method still has some weaknesses to be addressed:Firstly,there are some high frequency acoustic pressure noises in the solved flow fields.Furthermore,the SPH method has a lower computational efficiency,when paying attention to the details of the flows or calculating large-scale hydrodynamic problems,the computational cost is high,to some extent,which limiting the expansion of this method in high dimensions.With the development of computer technology,the demand for the simulation of fluid motion is increasing.The single-phase fluid flow simulations are no longer available for actual engineering requirements;however,the simulation of multiphase flow is often complicated by density discontinuity and viscosity discontinuity.In this paper,we study the single-phase sloshing problems by comparing several suppressing pressure oscillation algorithms.The single-phase sloshing model can exactly predict the pressure load on the tank wall and the kinetic properties of free surface,which was built by suited suppressing pressure oscillation algorithm and free surface capturing and wave elevation calculation algorithm.On the basis of this model,we study the effect of diverse suppressing sloshing devices on suppressing sloshing problems.This can provide a reference for the structural design of tank.To consider the characteristic of density discontinuity on the multi-intersection interface,we propose an improved multiphase SPH model,which can effectively suppress pressure oscillation.This model is available for multiphase fluid flow problems through a series of numerical simulation verification.Take into account the lower computational efficiency in SPH method,we develop an explicit coarse-grained distributed parallel program for WCSPH method based on the Message Passing Interface.The numerical results are accurate and reliable through debugging these parallel programs.These parallel WCSPH model can dramatically accelerating the numerical simulation problems such as large density differences fluid flow,fluid-solid interaction,free and moving border problems,large deformation free surface fluid flow problems,etc.In the simulation of a multiphase sloshing problem composed of 1000+thousands of particles,a ratio of acceleration approximates 12 times.