Settings for the Radiation in Participating Media Interface
The Label is the default physics interface name.
The Name is used primarily as a scope prefix for variables defined by the physics interface. Refer to such physics interface variables in expressions using the pattern <name>.<variable_name>. In order to distinguish between variables belonging to different physics interfaces, the name string must be unique. Only letters, numbers, and underscores (_) are permitted in the Name field. The first character must be a letter.
The default Name (for the first physics interface in the model) is rpm.
•
Radiative Heat Transfer in Finite Cylindrical Media: Application Library path Heat_Transfer_Module/Verification_Examples/
cylinder_participating_media
•
Radiative Heat Transfer in a Utility Boiler: Application Library path Heat_Transfer_Module/Thermal_Radiation/boiler
Participating Media Settings
To display this section select the Radiation in participating media check box under Physical Model on any version of the Settings window for Heat Transfer.
Radiation Discretization Method
Select a Radiation discretization method: Discrete ordinates method (the default) or P1 approximation.
•
When Discrete ordinates method is selected, Opaque Surface and Continuity on Interior Boundary are automatically added as default features.
•
When P1 approximation is selected, Opaque Surface is automatically added as a default feature and both this and Incident Intensity are made available from the Physics ribbon toolbar (Windows users), Physics context menu (Mac or Linux users), or the context menu (all users). Continuity on Interior Boundary is not available.
The choice of Radiation discretization method also offers different settings for the Radiation in Participating Media (Heat Transfer Interface) (all methods), Opaque Surface (P1 approximation), and Incident Intensity (P1 approximation) nodes.
Refractive Index
For either selection, define the Refractive index nr (dimensionless) of the participating media. The same refractive index is used for the whole model.
Performance Index
When Discrete ordinates method is selected, choose a Performance index Pindex from the list. Select a value between 0 and 1 that modifies the strategy used to define automatic solver settings. The default is 0.4. With small values, a robust setting for the solver is expected. With large values (up to 1), less memory is needed to solve the model.
Discrete Ordinates Method
When Discrete ordinates method is selected, choose the Discrete ordinates method order from the list. This order defines the angular discretization of the radiative intensity direction.
In 3D, S2, S4, S6, and S8 generate 8, 24, 48, and 80 directions, respectively. The default is S4.
In 2D, S2, S4, S6, and S8 generate 4, 12, 24, and 40 directions, respectively.
For additional background theory also see Discrete Ordinates Method (DOM), Discrete Ordinates Method Implementation in 2D, and P1 Approximation Theory.
Discretization
This section is available by clicking the Show button () and selecting Discretization.
When the Radiation discretization method is set to Discrete ordinates method in Participating Media Settings, set the discretization level of the Radiative intensity: Constant, Linear (the default), Quadratic, Cubic, Quartic, or Quintic.
When the Radiation discretization method is set to P1 approximation in Participating Media Settings, set the discretization level of the Incident radiation: Linear (the default), Quadratic, Cubic, Quartic, or Quintic.