Smoothed particle hydrodynamics (SPH) models

This is work by Georg Ganzenmuller at the Fraunhofer-Institute for High-Speed Dynamics at the Ernst Mach Institute in Germany. He has implemented the SPH package in LAMMPS to perform SPH simulations.

The first animation is of the classic dam break problem, where a column of water collapses. It is described more fully in this PDF guide.

The second movie is a chewing-like destruction of some sample sausage due to repeated application of an indenting cylinder. At the bottom of the container is a little bit of water.

The third animation is an SPH simulation of the same process. In the center panel frame, we have the container (gray), which is visualized sliced open in order to permit looking inside. Water is the light blue surrounding the yellow (sausage). The indenter is colored in magenta. This visualization looks like FEM because the SPH particles have been interpolated onto a regular grid, visualized via LLNL’s VisIt program. In the left panel, only water, sausage, and the container is shown. Water is colored according to salt content. As the sausage is ruptured and deformed during the indentation cycles, salt diffuses from the sausage into the water, which changes color accordingly. In the right panel, damage of the sausage is color-coded.

The physics contained in the food simulation is as follows:

Water and sausage particles are modeled using SPH, with Tait’s EOS.

The sausage has additional shear stability, by means of a Peridynamics-like approach using breakable bonds. The damage parameter shown on the right is akin to the Peridynamics damage parameter, proportional to the number of broken bonds.

A diffusion equation models the transport of salt from the sausage into the water. The diffusion coefficient is proportional to the damage parameter, because the rupturing process creates new surfaces which contribute to diffusion.