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Reference Guide
This manual provides a detailed list of all the input keywords and options available in Radioss.
Starter Input
This manual provides a list of all the model definition keywords and options available in Radioss.
General Controls
Block Format Keyword In this group, keywords are used to set default value, global parameter, analysis type, input/output print, damping and ALE and CFD treatment for the whole model. For default value, it is still possible to overwrite in each specific keywords.
ALE and CFD
/ALE/GRID
Block Format Keyword This card enables grid formulation for ALE modeling. The ALE domain can have moving boundaries.
/ALE/GRID/ZERO
Block Format Keyword Describes the Euler formulation.

Welcome
What's New
View new features for Radioss 2025.
Overview
Radioss^® is a leading explicit finite element solver for crash and impact simulation.
Tutorials
Discover Radioss functionality with interactive tutorials.
User Guide
This manual provides details on the features, functionality, and simulation methods available in Altair Radioss.
Reference Guide
This manual provides a detailed list of all the input keywords and options available in Radioss.
- File Extensions and Formats
  Current Radioss format uses the 12x extension format.
- Single File Input
  This format allows running either Starter or Engine with the same file.
- New Keywords in 2025
  New and modified features in Radioss.
- Starter Input
  This manual provides a list of all the model definition keywords and options available in Radioss.
  - 2D and 3D Analysis Options
  - Starter Keywords Syntax
    Block Format Keyword
  - Smooth Particle Hydrodynamics (SPH)
    The Smooth Particle Hydrodynamics method formulation is used to solve the equations of mechanics, when particles are free from a meshing grid.
  - Computational Fluid Dynamics (CFD)
  - General Controls
    Block Format Keyword In this group, keywords are used to set default value, global parameter, analysis type, input/output print, damping and ALE and CFD treatment for the whole model. For default value, it is still possible to overwrite in each specific keywords.
    - Formats
    - Default Value
      Keywords used to set the default value.
    - Computation
    - Input/Output
    - Damping
      Block Format Keyword In this group, keywords are used to set Rayleigh mass and stiffness damping coefficients, which apply to a set of nodes used to stabilize the results.
    - ALE and CFD
      - /ALE/CLOSE
        Block Format Keyword Describes the treatment of element closure.
      - /ALE/GRID
        Block Format Keyword This card enables grid formulation for ALE modeling. The ALE domain can have moving boundaries.
        /ALE/GRID/DISP
        Block Format Keyword The displacement of a grid node depends on the displacements of the neighboring grid nodes.
        /ALE/GRID/DONEA
        Block Format Keyword Velocity of a given grid node depends on velocity and displacements of neighboring grid nodes.
        /ALE/GRID/FLOW-TRACKING
        Block Format Keyword Mean velocity within ALE mesh is used to determine automatically mesh displacement, mesh deformation, and also mesh rotation. The general idea is to have an ALE mesh acting as a tracking window.
        /ALE/GRID/LAPLACIAN
        Block Format Keyword ALE grid smoothing using the Laplacian smoothing method for 2D and 3D elements.
        /ALE/GRID/SPRING
        Block Format Keyword Grid nodes are connected with nonlinear springs (those springs have no effect on the material, only on the movement of the grid).
        /ALE/GRID/STANDARD
        Block Format Keyword Describes the standard formulation for ALE grid velocity computation.
        /ALE/GRID/VOLUME
        Block Format Keyword Ale grid smoothing formulation is based on volume. Each ALE node position is computed as the average position of the centroids of the elements to which it is connected. The volume of the elements is used to weight the average positions.
        /ALE/GRID/ZERO
        Block Format Keyword Describes the Euler formulation.
      - /ALE/MUSCL
        Block Format Keyword This option allows for a second order MUSCL (Monotonic Upstream-Centered Scheme for Conservation Laws) reconstruction of volumic fraction fields when using Multi-Material laws (LAW51), and for a full second order scheme (time and space) when using material LAW151.
      - /ALE/SOLVER/FINT
        Block Format Keyword This option defines the numerical method for internal force integration. This is relevant only for brick element and ALE legacy solver (momentum equation solved with FEM).
  - Nodes
    Block Format Keyword In Radioss, two node types are available. They use Cartesian coordinate to describe the position of each node.
  - Elements
    Block Format Keyword
  - Component and Parts Organization
    Block Format Keyword In this group, keywords are used to combine material and property information (/PART), assemble model (/SUBSET) or define a separate model (//SUBMODEL).
  - Interfaces
    Block Format Keyword Interfaces solve the contact and impact conditions between two parts of a model. Several interface types are available in Radioss and use different contact treatments.
  - Materials
  - Properties
    Block Format Keyword
  - Monitored Volumes (Airbags)
    Block Format Keyword Monitored volumes can be used to model an airbag, tire, tank, or any closed volume.
  - Constraints
    Block Format Keyword Radioss supports several different kinematic constraints, which are mainly used to impose acceleration, velocity, displacement or temperature in structure or constraint the moving of structure. They are mutually exclusive for each degree-of-freedom (DOF). Two kinematic conditions applied to the same node may be incompatible.
  - Load Cases
    Block Format Keyword In Radioss the following load cases are available. Stress/strain as initial state could be considered by modeling, as well as pressure, gravity, and thermal load.
  - Tools
    Block Format Keyword In this group, tools like transformation, frames, skews, and curve are introduced.
  - Groups(Sets)
    Block Format Keyword Keywords in this group are used to define how to select a group of node, part, elements, lines, or surfaces.
  - Adaptive Meshings
    Block Format Keyword Adaptive Meshing is used in metal forming to divide the element to better describe the geometry. /ADMESH/GLOBAL and /ADMESH/SET are not available for SPMD computation.
  - Output Database
    Block Format Keyword Time histories output for different element groups, section output, or gauge output are described in this group.
- Engine Input
  This manual provides a list of all the solution definition keywords and options available in Radioss.
- LS-DYNA Input
  This manual provides a list of LS-DYNA input files available in Radioss.
- Multi-Domain
  This manual contains the description of the keywords for the Radioss Multi-Domain.
- Obsolete Keywords
  Keywords that are still supported, but no longer maintained (*) are considered obsolete.
- Other Files
- Definition
Example Guide
This manual presents examples solved using Radioss with regard to common problem types.
Verification Problems
This manual presents solved verification models.
Frequently Asked Questions
This section provides quick responses to typical and frequently asked questions regarding Radioss.
Theory Manual
This manual provides detailed information about the theory used in the Altair Radioss Solver.
User Subroutines
This manual describes the interface between Altair Radioss and user subroutines.

/ALE/GRID/ZERO

Block Format Keyword Describes the Euler formulation.

Format


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/ALE/GRID/ZERO

Comments

No calculation is performed on the grid.