Joseph Ha

Smooth particle hydrodynamics: status and future potential

SPH is a powerful mesh free method that is now able to solve very complex multi-physics flow and deformation problems in a broad number of fields. This paper concentrates on the use of SPH to simulate a broad range of complex industrial fluid flow problems. These include free surface fluid flow for the generation of digital content, geophysical flows such as volcanic lava flows and tsunamis, several types of die casting (gravity, high pressure and ingot casting), resin transfer moulding and flow in porous media, mixing of particulates in liquid, pyrometallurgy and slurry flow in semi-autogenous grinding mills. The strengths and weaknesses of SPH will be explored and future opportunities for using the method to make major modelling advances are discussed.

Flow modelling in casting processes

Abstract Advances in modelling of casting processes using smoothed particle hydrodynamics (SPH) are described. Three-dimensional simulations of high pressure die casting are presented for two realistic dies. Developments needed for both visualisation of these systems and for their simulation are described. Comparison of SPH and MAGMAsoft simulations with experimental results from water analogue modelling are made for gravity die casting. The SPH comparisons are particularly good, with the method able to capture the fine details of the free surface motion, including plume shape, frequency and phase of oscillation and the correct relative heights of all the free surfaces.

High pressure die casting simulation using smoothed particle hydrodynamics

Extensive two dimensional smoothed particle hydrodynamics (SPH) simulations of high pressure die casting are presented. SPH, being Lagrangian, is very well suited to these momentum dominated flows with complex free surface behaviour including fragmentation. The filling of three classes of die shapes with isothermal fluid is analysed for Reynolds numbers (Re) ranging from 50 to 50,000. Realistic and very complex flow patterns with recirculations, vortices, back filling, droplet and fragment formation are predicted. Many classes of casting defects can be explained by these flow patterns. Invariance of the numerical results to simulation resolution is demonstrated. Finally, a water analogue experimental set is described and used to produce data with which to validate the numerical predictions. These comparisons are very favourable.

Comparison of SPH simulations of high pressure die casting with the experiments and VOF simulations of Schmid and Klein

SPH simulations of die filling for three geometries previously studied by Schmid and Klein are compared to their experimental and numerical results. The agreement with experiment for both numerical methods is very good, but the SPH solutions tend to capture free surface and void shapes modestly better than the VOF and also predict small scale structure better. These result from the Lagrangian nature of SPH and the superior mass conservation properties of this particle method.

Simulation of suspension of solids in a liquid in a mixing tank using SPH and comparison with physical modelling experiments

This paper demonstrates the use of Smoothed Particle Hydrodynamics (SPH) to simulate a suspension of solids in a liquid mixing tank when the solids are large and have a high loading in comparison with the liquid in the tank. The simulations are validated by comparing the results with physical modelling experiments that shows a relationship between the submergence criterion of the solids and the impeller speed. The experiments were conducted using water as the fluid and cylindrical blocks of wood with a specific gravity of 0.5 with near identical conditions being used for the simulations.

Three dimensional modelling of high pressure die casting

The modelling of high pressure die casting using SPH is extended to three dimensions. This increases the complexity of the geometry specification and the visualisation, but not of the simulation method. Filling of four simple die/gate combinations is presented. The dies range from a rectangular cavity to a simple machinery component.

Three-dimensional smoothed particle hydrodynamics simulation of high pressure die casting of light metal components

Abstract In this paper we present the extension of smoothed particle hydrodynamics (SPH) modelling of high pressure die casting (HPDC) to both three-dimensions (3D) and to realistic die geometries. The SPH method is well established in other areas and is now used for HPDC. The SPH method (in 3D) and the methodology used to represent complex three-dimensional die shapes are described. The use of this SPH system to model the filling of a representative generic HPDC component is presented. The importance of the order of the die filling, first seen in two dimensions, is demonstrated as is the role of flow separation from corners and even moderately curved surfaces. The degree of surface fragmentation, droplet formation and the strongly transient nature of the voidage are also shown. Finally the filling of the runner, gate and die for a real automotive piston head from an automatic transmission is shown and the difficulties inherent in such large scale computations are discussed.

Simulation of high pressure die filling of a moderately complex industrial object using smoothed particle hydrodynamics

Abstract The present study reports on the extension of smoothed particle hydrodynamics (SPH) of high pressure die casting to realistic three-dimensional components. Predictions of the isothermal filling of a moderately complex die in 3D demonstrates the importance of flow separation off corners, edges and faces with high curvature and the non-intuitive order of fill resulting from complicated back flows. The free surface behaviour involves significant transient void formation and free surface fragmentation. The predictions are shown to be insensitive to the Reynolds numbers. Their accuracy is confirmed by comparing simulations with coarser and finer resolutions.

Computation of turbulent reactive flows in industrial burners

This paper presents models that are suitable for computing steady and unsteady gaseous combustion with finite rate chemistry. Reynold averaging and large eddy simulation (LES) techniques are used to model turbulence for the steady and unsteady cases, respectively. In LES, the Reynold stress terms are modelled by a linear combination of the scale-similarity and eddy dissipation models while the cross terms are of the scale-similarity type. In Reynold averaging, the conventional k–ϵ two-equation model is used. For the chemical reactions, a 3-step mechanism is used for methane oxidation and the extended Zeldovich and N2O mechanism are used for NO formation. The combustion model is a hybrid model of the Arrhenius type and a modified eddy dissipation model to take into account the effects of reaction rate, flame stretch and turbulent intensity and scale. Numerical simulations of a flat pulse burner and a swirling burner are discussed.

3-Dimensional SPH Simulations of High Pressure Die Casting

Three dimensional modelling of high pressure die casting (HPDC) using SPH is presented. The SPH method used to simulate three dimensional fluid flow is described. Three examples of HPDC are shown. The first is a generic component, the second is a real automotive piston head and the third one is a rack and pinion steering column. In each case the filling of the runner, gate and die are shown. The importance of the order of the die filling is shown as is the role of flow separation from corners and even moderately curved surfaces. The degree of surface fragmentation, droplet formation and the strongly transient nature of the voidage are also shown.