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User Guide
This manual provides details on the features, functionality, and simulation methods available in Altair Radioss.
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.

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Radioss^® is a leading explicit finite element solver for crash and impact simulation.
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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.
- 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.
  - SPH Cells Distribution
    The particles should be created in a hexagonal compact, face centered cubic or a cubic net packing.
  - Maximum Stored Number of Neighbors
  - SPH Symmetry Conditions
  - Solid to SPH Option (Sol2SPH)
    The solid to SPH option (Sol2SPH) enables you to turn a solid element into particles in order to increase the time step/robustness of a Lagrangian calculation, while not significantly changing the physics.
- 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.

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.

It is specially adapted to simulate phenomena with a very substantial deformation, that is a range of applications where the Finite Element method, with ALE and Lagrangian formulation, loses' its efficiency and accuracy.

The SPH method built in the Radioss code is compatible with most functions. For instance, it is possible to cause two objects to interact, one discretized by finite elements and the other by particles.

You can put the SPH formulation in an ALE model, only if the boundary between SPH and ALE is Lagrangian. The SPH formulation is only available in 3D analysis.