Converting to Smoothed Particles

Converting from Lagrangian finite elements to smoothed particles allows for model separation to match real-world behavior.

Before you begin: The mesh elements to be converted must be hexahedron (brick), linear wedge, or tetrahedron types. Smoothed particles are used only in explicit dynamic analyses.
See Also
Ordered Geometric Sets
In Other Guides
About the Material Palette Interface
  1. From the Properties section of the action bar, click SPH Particles .
  2. Optional: Enter a descriptive Name.
  3. Select a geometry support.

    A particle conversion is applied to a solid body. You can also use geometry from an ordered geometric set.

    If the support you select already has a material assigned to it, the Material field displays the material that is applied to the support.
  4. Optional: If no material is assigned, or if you want to override the existing material assignment, do the following:
    1. Click .
      The Material Palette appears.
    2. Search for the material you want to assign, and click it.
    3. Click OK to close the Material Palette.
    The Material field displays the newly applied material.
  5. Choose a particle generation method:

    On background grid
    Creates a uniform distribution of particles based on a grid size and orientation.
    Per element
    Creates a specified number of particles for each Lagrangian finite element being converted.

  6. For background grid conversion, specify the following:
    1. Particle thickness type, Uniform or Variable.

      For more information, see About Smoothed Particle Hydrodynamics (SPH).

    2. Enter a value for the Grid spacing.

      The grid spacing determines the positioning and the maximum size of the particles.

    3. Choose an Grid orientation definition, Global or Local to specify an axis system for the background grid.

      The global axis system has a constant orientation defined for the entire model. A local axis system is defined with a displacement or rotation from the global system and might move with a portion of the model during deformation. Local axis systems must be defined in another app. For detailed information, see Defining an Axis System in the Simulation Model Preparation guide.

    The conversion will be completed at the start of the simulation.
  7. For per element conversion, specify the following:
    1. Select the number of Particles per isoparametric direction.

      Values from 1 to 7 are allowed. For more information, see About Smoothed Particle Hydrodynamics (SPH).

    2. Enter the time Criterion for when the conversion to particles should take place.

      A time of 0 corresponds to conversion at the start of the simulation. A later time for conversion might make sense if the simulation event requiring particle conversion takes place after other steps where finite elements are appropriate.

      The conversion will take place at the specified time in the simulation.
  8. Select the Function order for SPH particle formulation.

    Choose from second order (quadratic), third order (cubic), or fifth order (quintic).

  9. Optional: Specify Material orientation options.

    Option Description
    Specify orientation If the materials in your model exhibit directional properties, you can define their orientation.
    Axis system definition There are several axis system choices:
    Global
    Defined by a constant orientation for the entire model.
    Local
    Defined by a displacement or rotation from the global system. It might move with a portion of the model during deformation.
    Face and edge
    Defined by selecting faces and edges and specifying their relation (creates a spatially varying orientation).
    For example, select a surface or face to define the normal axis and the normal at the point closest to your selection is used as the normal axis direction. Select an edge to define the primary axis; the point on the edge closest to your selection defines the tangent used as the primary axis construction direction.
    The axis system follows the selected face and edge through motion and deformation of the model and recalculates axis locations according to their relative motion.
    Notes: For shell sections and membrane sections, the element normal is always preserved. The axis following the normal direction is projected onto the surface as the 1-direction. The 2-direction is the cross-product of the element normal and the 1-direction.

    Face and edge selection is not available for axisymmetric models.
    Axis system Local axis systems must be defined in another app. For detailed information, see Defining an Axis System in the Simulation Model Preparation guide.
    Axis system type Cartesian specifies an axis system where each point is located relative to an origin and to three planes that intersect at right angles to the origin. Cylindrical specifies a local axis system where points are located based on their distance from a reference axis.
    Note: This option is relevant only for non-axisymmetric models. Axisymmetric models use a Cartesian axis system.
    Axis for rotation An axis for additional rotation of the axis system. For Face and edge systems, this axis is the same as the normal direction definition.
    Additional rotation Positive rotation is measured using the right hand rule. You can enter a value in radians (rad) to convert it to degrees.

  10. Click OK.