Two-Phase MPS Method for Dam-Break Flows

In this paper, a new multiphase MPS-GPU method is proposed through the combination of moving particle semi-implicit (MPS) method and Graphics Processing Unit (GPU) acceleration technique. The new method not only inherits the advantage of MPS method in capturing complex interface deformations, but also overcomes the limitations of huge computational cost in three-dimensional MPS simulation. By this method, both the two-layer-liquid and three-layer-liquids sloshing problems are simulated three-dimensionally on the GPU device, in which more than one million of particles are included. In simulations, the sloshing patterns of each liquid layer under different external excitations are accurately captured. From the interface elevations and impacting pressures calculated by present method, it is found that an obvious discrepancy exists between the deformations of free surface and phase interfaces. Then, the results obtained by multiphase MPS-GPU method are compared with experimental data and other numerical results in open literature and a good agreement is achieved, which validates the accuracy and applicability of the present method in three-dimensional simulations of multi-layer-liquid sloshing flows.

Step-by-step improvement of MPS method in simulating violent free-surface motions and impact-loads

The energetic fuel-coolant interaction (FCI) has been one of the primary safety concerns in nuclear power plants. Graphical processing unit (GPU) implementation of the moving particle semi-implicit (MPS) method is presented and used to simulate the fuel coolant interaction problem. The governing equations are discretized with the particle interaction model of MPS. Detailed implementation on single-GPU is introduced. The three-dimensional broken dam is simulated to verify the developed GPU acceleration MPS method. The proposed GPU acceleration algorithm and developed code are then used to simulate the FCI problem. As a summary of results, the developed GPU-MPS method showed a good agreement with the experimental observation and theoretical prediction.

The present paper describes the simulation of behavior of mooring vessels in tsunami using the 3-D MPS (Moving Particle Semi-implicit) Method for considering leading wave and backwash effect. The chain of a disaster is brought about by two kinds of tsunami. The chain of disaster means breaking the mooring tether, grounding on a wharf, drift to continental areas, the collision with building by leading wave and the outflow of the floating matter by backwash. In this research, the 3D-MPS method is applied, and the bore like wave is applied as an assumed tsunami. The expression of backwash is tried by water pillar collapse. The present calculation results are compared with the experimental results and the applicability of the MPS method is discussed. In addition, the vehicle is arranged on a wharf, and the chain of disaster is simulated.

Numerical simulation of the SURC-2 and SURC-4 MCCI experiments by MPS method

Coupling of rigid body dynamics and moving particle semi-implicit method for simulating isothermal multi-phase fluid interactions

Comparison investigations of numerical simulations of incompressible viscous flows by the SPH (smoothed particle hydrodynamics) and the MPS (moving particle semi-implicit) are presented. A dam-break problem is chosen as the test case. In the calculation with the SPH method, weakly compressible model is used, i.e. WCSPH, which describes water as a nearly incompressible fluid, while in MPS method, the pressure Poisson equation is introduced to keep the density of fluid to be constant. The numerical results show that the two particle methods are robust and flexible, numerical results qualitatively agree with the experimental data. It can be seen that both the SPH method and the MPS method can be easily applied to the complex free surface flow problems.

A conservative finite volume-particle hybrid method for simulation of incompressible interfacial flow

The reliability of a micro-solder joint in a semiconductor structure depends on its solder shape. Therefore, many methods of predicting the molten-solder shape have been proposed. However, conventional methods cannot be used to accurately predict the shape of a miniaturized solder. In a miniaturized solder joint, molten solder greatly changes its shape during the reflow process, and even topology changes (e.g., merging with another solder in a neighboring joint or splitting into several pieces) might occur. Conventional methods cannot be used for expressing these phenomena. To predict a miniaturized solder shape, we developed a new shape-prediction method based on the moving-particle semi-implicit (MPS) method. In the MPS method, a continuum is expressed as an assembly of particles. In contrast to finite element analysis (FEA), our new method can easily express large deformation and topology changes because the continuum does not need to be divided into elements. Moreover, we evaluated the fracture life of a solder joint with the predicted solder shape by coupling our shape-prediction method with a crack-propagation analysis method that we also developed. The crack-propagation is used for automatically calculating a crack-initiation point and crack-propagation paths, and the fracture life is evaluated quantitatively. We applied this coupling method to evaluate fracture lives of various solder joints and found that a difference in solder shape caused a difference in crack-initiation points, crack-propagation paths, and fracture lives.

A higher-order moving particle semi-implicit (MPS) method was developed to solve water entry problems. The Wendland kernel function was applied in the particle interaction model. Various models for pressure gradient were investigated. To overcome the inconsistency in the original MPS methods, a pressure gradient correction was implemented to guarantee the first-order consistency of gradient. The corrective matrix was modified by using the derivative of the kernel function. A particle shifting technique was also applied to improve the numerical stability. Validation studies were carried out for water entry of a rigid wedge with the tilting angles of 0°, 10° and 20°, and a rigid ship section. The solutions by the present method are generally in good agreement with experimental data and other published numerical results.

Sponsored by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan, a computer code, named COMPASS, has been developed employing the Moving Particle Semi-implicit (MPS) method for various complex phenomena of core disruptive accidents (CDAs) in sodium-cooled fast reactors (SFRs). The COMPASS is designed to analyze multi-physics problems involving thermal hydraulics, structure and phase change, in a unified framework of MPS method. In this and the following five papers [1–5], the outcomes of the project in FY2006 are presented. In FY2006, development of the basic functions of the COMPASS was completed and fundamental verification calculations were carried out. In this paper, the outline of the project and a part of COMPASS, the structural mechanics part, are described, including formulation of MPS method and the conceptual design of COMPASS, and the results of the basic verification calculations for structural mechanics module.

Moving Particle Semi-implicit (MPS) method is a particle method which has been developed to analyze incompressible flows with free surfaces. Fluids are represented by particles which move in fully Lagrangian description. Since grids are not necessary, complex motion of free surfaces can be calculated without grid tangling or numerical diffusion. In the MPS method, a differential equation system is transformed to particle dynamics using the models representing differential operators. Incompressibility is solved by the Poisson equation of pressure to keep the particle number density constant. Solid mechanics is also modeled by particles and fluid-structure interaction can be solved. Calculation examples are provided in this paper: collapse of a water column, melt droplet fragmentation, sloshing with tank deformation, nucleate boiling and droplet breakup. These examples show that the MPS method is a powerful tool to investigate complex behaviors of free surfaces and multiphase flows.

In this paper, numerical improvements are implemented for solving for the pressure in the moving particle semi-implicit (MPS) method for free-surface flow simulations. The tensile instability problem is solved using a dynamic stabilization (DS) algorithm. The low numerical diffusion of this algorithm is shown through numerical tests. A free-surface treatment that includes an accurate free-surface particle detection algorithm and the implicit application of a free-surface boundary condition is used. The solution of the Navier–Stokes equation is improved using a particle shifting (PS) algorithm. The proposed MPS method for free-surface flow simulations is successfully applied in several benchmark tests and two- and three-dimensional dam break problems. The numerical simulation results agree well with the analytical and empirical ones. It is shown that the proposed MPS method effectively improves the stability and accuracy of simulations of free-surface flows.

PurposeThe paper aims to apply a modified version of the MPS method to a double-dam-breaking test in which high dispersion zones and high natural clusterization zones are present, such as when the water column collapses into two sides and the two solitary waves collide, respectively.Design/methodology/approachThe work takes advantage of the mixed source term from the cheaper computational version of the moving particle semi-implicit (MPS) method to reduce one step from the MPS classical algorithm. The proposed test can be successfully simulated by applying modifications to the variance parameter in the Laplacian operator and gradient model.FindingsThe results show stable behavior in dispersion and clusterization zones. Also, the collision and merging produced by solitary waves was successfully simulated.Research limitations/implicationsThe main limitation in this work was the development of a comparison between the obtained results and the simulations with the original cheaper computational version of the MPS, this limitation is due to the overestimation of inter particle repulsive forces from its gradient model.Practical implicationsThe application of solitary waves is of paramount importance in a number of applications, and this stems from the fact that the interaction of solitary waves with ships and other floating structures could generate highly deformed and complex free surface flows.Social implicationsFor future work, the modified version of the MPS method can be applied in flow over sill base simulations, in close and open channels, and in simulating breaking waves to determine impact pressures by using solitary wave propagation.Originality/valueThe simulation of interaction of large groups of particles as in the case when two solitary waves collide could cause severe instability problems in pressure, causing the computer analysis to stop. MPS classical algorithm takes into account an explicit step that, in this case, may provoke the problem. For this reason, the cheaper version of MPS method is used to correctly simulate solitary wave interactions.

The formation of holographic surface relief gratings (SRGs) on azobenzene containing polymers are simulated using the moving particle semi-implicit (MPS) method. The gradient force of optical electric field and the influence of surface tension were considered as the driving forces for mass transport. The particle motions of SRG formation are calculated by giving particles two beams interference with various polarization states. The model for time evolution of SRG formation coincided with experimental results qualitatively.