Home
User Guide
This manual provides details on the features, functionality, and simulation methods available in Altair Radioss.
Explicit Structural Finite Element Analysis
In this section, available explicit features for different explicit analyses are presented.
Airbag Modeling
Airbags are modeled as monitored volumes /MONVOL in several different ways.
Monitored Volume (/MONVOL)
A monitored volume is defined with one or more shell (3-node or 4-node) parts.
FVMBAG1
A non-uniform pressure is assumed inside the volume. The gas flow in FVMBAG1 is solved using a finite volume integration scheme which allows the gas flow through the airbag to be correctly modeled.

Welcome
What's New
View new features for Radioss 2024.1.
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.
- Run Radioss
  The Radioss solver can be executed using different methods described here.
- Explicit Structural Finite Element Analysis
  In this section, available explicit features for different explicit analyses are presented.
  - Time Step
    An explicit is solved by calculating results in small time increments or time steps. The size of the time step depends on many factors but is automatically calculated by Radioss.
  - Finite Elements
  - Modeling Tools
  - Materials
    Different material tests could result in different material mechanic character.
  - Failure
  - Composites
    Composite materials consist of two or more materials combined each other. Most composites consist of two materials, binder (matrix) and reinforcement. Reinforcements come in three forms, particulate, discontinuous fiber, and continuous fiber.
  - Connections
  - Kinematic Constraints
    In Radioss, a kinematic condition is a nodal constraint applied to a set of nodes.
  - Interfaces
    Several interfaces are available in Radioss, this section deals with contact interfaces only. Each interface is distinguished with a type number.
  - Loads
  - Airbag Modeling
    Airbags are modeled as monitored volumes /MONVOL in several different ways.
    - Monitored Volume (/MONVOL)
      A monitored volume is defined with one or more shell (3-node or 4-node) parts.
      - AIRBAG1
      - COMMU1
        This option is used to simulate chambered airbags and may be used to unfold an airbag.
      - FVMBAG1
        A non-uniform pressure is assumed inside the volume. The gas flow in FVMBAG1 is solved using a finite volume integration scheme which allows the gas flow through the airbag to be correctly modeled.
      - GAS
        This monitored volume is typically used to model tire pressure or simple fuel tank.
      - LFLUID
        A linear fluid monitored volume which models a volume filled with fluid.
      - PRES
        A simple perfect gas monitored volume where the relative pressure is a function of relative volume or a function of time.
    - Monitored Volume Time Step
      An "AIRBAG1" time step is estimated into the Engine, but this time step will never control the time step during the run. If that is the case, it means there is a non-physical airbag definition in the input deck.
    - FVMBAG1 Airbag Modeling Guidelines
    - Tank Test
      By using data from a tank test output, it is possible to obtain the temperature and the mass flow of the gas supplied, which can be used as input to Radioss.
    - Airbag Setup Recommendation
    - Airbag Deployment Debugging
      The objective here is to provide some guidelines on how to troubleshoot a simulation where the airbag does not deploy properly or crashes because of the airbag.
  - Debugging Guidelines
  - Appendix
- Implicit Structural Finite Element Analysis
- Fluid and Fluid-Structure Simulation
  In this section, fluid and fluid-structure simulation is presented.
- 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.
- Multi-Domain Technique
  The objective of the Multi-Domain technique (also referred to as RAD2RAD) is to optimize the computing performances of large scale Radioss models.
- Design Optimization
  Optimization in Radioss was introduced in version 13.0. It is implemented by invoking the optimization capabilities of OptiStruct and simultaneously using the Radioss solver for analysis.
- Error Message Database
  This section is comprised of error messages in ascending numerical order.
- Engine Error Messages
- Warning Message Database
  This section is comprised of warning messages in ascending numerical order.
Reference Guide
This manual provides a detailed list of all the input keywords and options available in Radioss.
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.

FVMBAG1

A non-uniform pressure is assumed inside the volume. The gas flow in FVMBAG1 is solved using a finite volume integration scheme which allows the gas flow through the airbag to be correctly modeled.

Since the gas flow simulated, the unfolding and deployments behavior is correct which is needed for out of position occupant simulations and curtain airbag deployments.

Perfect gas law and adiabatic conditions are assumed. Injected mass, velocity and temperature are defined as a time function. The injected velocity is obtained using:

v_{i n} (t) = \frac{\frac{d m (t)}{d t}}{S ρ_{i n} (t)}

Where, S is the injector surface.

A sensor may define the inflator starting time.

Deflation of vent hole is available after reaching a pressure (P_def) or time (t_def) criteria.

In this version, heat gas capacity C_p is assumed constant.

More further detail, refer to FVMBAG1 Airbag Modeling Guidelines.