Smooth Particle Hydrodynamics Panel

Location: 1D page

Note: Available in the Radioss, PAM-CRASH 2G, and LS-DYNA solver interfaces.

Smooth Particle Hydrodynamics (SPH) is a technique used to analyze bodies that do not have high cohesive forces among themselves and undergo large deformation, such as liquids and gases.

In SPH Finite Point Method (SPH FPM), a given volume of the body of interest is discretized into particles, called SPH elements. These elements are node-like particles which have no geometric connectivity among themselves. Each SPH element has an effective mass. The summed mass of all particles in the filled volume of the body should be equal to the mass of the filled volume.

Panel Options

Option	Action
entity selector	Select the entities that define the volume to be filled with SPH elements.
use reference	SPH elements are generated at the corners/face centers of the cubes which fall within the user defined criteria. Select this checkbox to specify which point the generation of cubes should be started. The base point defines the starting point for cube generation, and is utilized by the mesher as a starting point. global origin Uses (0, 0, 0) for the reference point. local origin Define node coordinates for the reference point.
mesh orientation	Choose a method for defining the orientation of SPH elements. global system Use the default global system to align generated SPH elements. local system Define reference systems local to the model orientation. Generated SPH elements are aligned using the user defined local system.
pitch	Choose a method for specifying the distances between each SPH particle. simple cubic Arrange SPH particles in groups of 8, each particle being a corner of a cube. face centered cubic Arrange the particles in groups of 14, forming the corners and the center of each face of a cube. This is similar to a hexagonal close packed (HCP) structure and is recommended for use in Radioss models. Note: Smaller numbers will result in more elements within the same space, but this will not affect the mass or density of the substance (gas, fluid, and so on) that the particles represent.
material density= / filled volume mass=	Choose a method for specifying the quantity of fluid. material density= Specify its density (the total mass is then determined by the volume filled). filled volume mass= Specify its total mass (volume and density is determined by the model volume filled).
volume definition	Choose which elements to generate SPH elements for. all Generate SPH elements in all of the volumes in the model. enclosed Generate SPH elements in the volumes enclosed by the defined nodes, and ignores the remaining volumes. Nth Largest Specify which volumes to generate SPH elements in by defining the wrap size index in terms of volume size. Specify the largest volume by entering `1`; specify the second largest volume by entering `2`. exclude enclosed Ignore the volume(s) enclosed by the defined nodes and generate SPH elements in the remaining volumes.
partial fill	Model a fluid or gas that does not completely fill the selected volume. If enabled, perform the following steps: Choose between percent and depth. Percent Percentage of the volume to fill. Depth Depth of the volume to fill. Specify a percentage/depth of the volume to fill. Calculation of the volume is based on the lowest point of the model, parallel to the user defined plane. Use the plane and vector selector to define the direction of fill, which is generally the opposite of the direction of gravity when the filled volume is installed in the real world. If the particle mass is filled along the correct axis, but in the wrong direction (for example from the top of a fuel tank downward) click reverse direction to fix this. Figure 1.
wall offset	Create SPH particles up to a distance that you specify. The thickness of SPH elements is created from input. The distance between the SPH particles is driven by the pitch. Figure 2.
external to volume	Create SPH particles outside of the defined volume. Note: Available when wall offset is enabled, which enables the capability to offset SPH elements from selected volume surfaces. Figure 3.
wall clearance	Create SPH particles from the specified distance. Tip: Useful when you are trying to avoid contact of SPH elements with walls at the beginning of the solver run (1st iteration) and want the solver to run smoothly. Figure 4.

Command Buttons

Button	Action
create	Create a new SPH analysis.
reject	If the particle fill is incorrect, click reject. Note: Once you exit the panel you will no longer be able to reject the fill.
return	Exit the panel.