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Reference Guide
This manual provides a detailed list of all the input keywords and options available in Radioss.
Multi-Domain
This manual contains the description of the keywords for the Radioss Multi-Domain.
Multi-Domain Multi Input File Format
/DOMAIN
Multi-Domain Keyword Specifies the Radioss model name and the list of external links defined in its Starter input deck.

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.
- 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.
  - Multi-Domain Single Input File Format
  - Multi-Domain Multi Input File Format
    - /DOMAIN
      Multi-Domain Keyword Specifies the Radioss model name and the list of external links defined in its Starter input deck.
    - /END
      Multi-Domain Keyword This keyword has to be set at the end of the Multi-Domain.
    - /EXTERN/LINK
      Multi-Domain Keyword Defines the interfaces between the current model and other domains.
    - /LINK
      Multi-Domain Keyword Defines the type of connection used and the interface cross-references between specified domains.
    - /MESH
      Multi-Domain Keyword Defines the space of Lagrange multipliers in the case of incompatible meshes.
    - /MLTPS/ON
      Multi-Domain Keyword Activates the multi-scale time step option, which allows each domain to use its own time step.
    - /PRINT
      Multi-Domain Keyword Specifies the RAD2RAD printout frequency.
    - /PROC
      Multi-Domain Keyword Number of Processors used by the RAD2RAD executable.
    - /RADIUS
      Multi-Domain Keyword Allows to specify the value of the search radius.
    - /TIMEOUT
      Multi-Domain Keyword Allows you to specify the value of the timeout parameter for the establishment of the connection between RAD2RAD and Radioss Engine.
- 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.

/DOMAIN

Multi-Domain Keyword Specifies the Radioss model name and the list of external links defined in its Starter input deck.

Format

/DOMAIN/Rootname

Link_ID1, Link_ID2, Link_ID3, and so on.

Definition


Field	Contents	SI Unit Example
`Rootname`	Radioss model name (the root of the Starter file Rootname_0000.rad).
`Link_ID`	/EXTERN/LINK identifier