/ALE/GRID

Block Format Keyword This card enables grid formulation for ALE modeling. The ALE domain can have moving boundaries.

The grid must also be updated on each cycle to map the new geometric domain. This update is not unique and can be arbitrary. Grid points are updated at each cycle depending on formulation type defined.

Format

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/ALE/GRID/FormulationType

Definition

Formulation Type
Description
DISP
Average displacement.
DONEA
Donea formulation.
FLOW-TRACKING
ALE mesh motion and deformation.
LAPLACIAN
Laplacian grid smoothing method.
SPRING
Springs are introduced on cell edges to avoid locally small mesh size.
STANDARD
Advanced formulation with edge spring and anti-shear spring to avoid small mesh size and flat cells.
VOLUME
Volume based grid smoothing.
ZERO
Grid is not updated.

Comments

  1. ALE formulation is activated for a given material using /ALE/MAT card or using flag Iale in /PROP/TYPE14 (SOLID).
  2. If /ALE/GRID card is not specified in the input deck, the ALE grid formulation is automatically set as DISP (/ALE/GRID/DISP), with default values.
  3. The purpose of grid formulation is to update grid points with evolution of the ALE domain caused by moving boundaries (illustrated below). Grid velocities are also computed with a dependency on Lagrangian node velocities. Material inside the domain is not affected since it is remapped inside the new grid configuration at each cycle. Some domain evolution may lead to small cell and then numerical strategies can be introduced to mitigate time step decrease (example:/ALE/GRID/STANDARD).
    Figure 1.

    ale_grid
  4. Specific rules for grid velocity of given points can also be defined by introducing links (/ALE/LINK/VEL). This enables linking grid velocity to specific main nodes.
  5. A given point from ALE domain can be defined as a Lagrangian node (/ALE/BCS).
  6. A given grid point can be fixed in all or specific directions (/ALE/BCS).
  7. To fix material at a given point in a specified direction (/BCS).