The Heat Transfer with Radiation in Participating Media Interface
The Heat Transfer with Radiation in Participating Media (ht) interface (), found under the Heat Transfer>Radiation branch (), is used to model heat transfer by conduction, convection, and radiation, including radiation in participating (semi-transparent) media.
Whereas The Radiation in Participating Media Interface requires the temperature field as model input, this physics interface computes it. If the medium does not participate in the radiation (transparent medium), then use The Heat Transfer with Surface-to-Surface Radiation Interface instead.
A Solid model is active by default on all domains and when the Radiation in participating media check box is selected for the Heat Transfer interface. All functionality to include other heat transfer models, like Fluid, is also available.
The radiative intensity equations defined in participating media domains are approximated either with the Rosseland approximation, P1 approximation, or discrete ordinates method.
The following default nodes are added to the Model Builder: Solid, Initial Values, Thermal Insulation, Opaque Surface, and Continuity on Interior Boundary. Then, from the Physics toolbar, add other nodes that implement, for example, boundary conditions. You can also right-click Heat Transfer with Radiation in Participating Media to select physics features from the context menu.
Physical Model
When this physics interface is added, the Radiation in participating media check box is selected by default, which enables the Participating Media Settings section.
Ambient Settings
See Ambient Settings for details.
Consistent Stabilization
This section is available by clicking the Show button () and selecting Stabilization. See Consistent Stabilization for more details.
Inconsistent Stabilization
This section is available by clicking the Show button () and selecting Stabilization. See Inconsistent Stabilization for more details.
Participating Media Settings
Radiation Discretization Method
Select a Radiation discretization method: Discrete ordinates method (the default), Rosseland approximation, 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.
•
When Rosseland approximation is selected, neither Continuity on Interior Boundary nor Opaque Surface is included or 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
For Discrete ordinates method select 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
For Discrete ordinates method, select an 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, Rosseland Approximation Theory, and P1 Approximation Theory.
Discretization
This section is available by clicking the Show button () and selecting Discretization. By default, the shape functions used for the temperature are Quadratic Lagrange. See Discretization for more details.
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.
Dependent Variables
See Dependent Variables for details.
See Settings for the Heat Transfer Interface for a description of all the settings.