The procedure for defining a sub-model is as follows:
In the task menu, select the Define sub-models menu item.
Define sub-models
If you need to define a topo-object, follow the procedure outlined in Defining a Topo-Object.
If your simulation will involve a porous jump sub-model, define the necessary material dataset by following the procedure outlined in Defining a Material Dataset.
Select the Create a new sub-model menu item.
Create a new sub-model
Select the appropriate sub-model type.
V or F imposed
Temperature imposed
Heat flux density imposed
Heat conduction problem
Pointwise velocity imposed
Coordinates imposed
Diffuse gray wall imposed
Porous jump model
See Types of Sub-Models for a description of the sub-model types.
When prompted, specify a title for the sub-model.
Specify the domain of the sub-model.
Domain of the sub-model
You can select from the topo-objects that are available in the mesh. These can be PMeshes that were generated during the original mesh generation, topo-objects that you created in Ansys Polydata (as described in Defining a Topo-Object), or intersections between boundary sets and subdomains in the mesh. Note that the notation S1*B2 indicates the intersection between subdomain 1 and boundary set 2.
Important: Note that for the imposed diffuse gray wall sub-model, only PMeshes can be selected for the domain.
Specify the parameters related to the sub-model type you have chosen:
For an imposed velocity sub-model, the inputs are as follows:
Velocity components imposed
For Cartesian velocity components, keep the default mode and specify the value of
, 
, and (in 3D) 
. For normal/tangential velocity components, select Enable Normal/Tangential Mode and then specify the value of
and 
.
For an imposed temperature sub-model, the inputs are as follows:
Temperature imposed
Specify the temperature as a constant or as a linear function of coordinates.
For an imposed heat flux sub-model, the inputs are as follows:
Heat flux density coefficients
Enter the coefficients for the equation shown in the Ansys Polydata interface.
For a heat conduction sub-model, the inputs are as follows:
Specify the matrix coefficients for the anisotropic conductivity.
Anisotropy matrix coefficients
The conductivity can either be a scalar, in which case the anisotropy matrix is the unit matrix, or a tensor. If it is a tensor, the conductivity matrix (which must be positive-definite) is the product of the scalar conductivity and the matrix specified here. You need to specify the scalar components of the matrix.
Specify the thermal conductivity.
Thermal conductivity
Specify the shell thickness/area.
Shell thickness
Because the volumetric conductivity is entered for all heat conduction sub-models, the equations must be multiplied by the shell thickness (2D) or by the wire section area (1D) before being added to the energy equation.
For an imposed pointwise velocity sub-model, the inputs are the local requested velocity and the penalty coefficient (which must be high enough to impose the velocity effectively on the sub-model domain).
For an imposed coordinates sub-model, the inputs allow you to fix any of the components of the coordinates (that is, if you fix the
-component, the message displayed will be
Constraint on X-component: dX=0) or let any component be free (that is, if you let the
-component be free, the message displayed will be
No constraint on X-component).For an imposed diffuse gray wall sub-model, the inputs include the transmittance of the boundary (
in Equation 13–15), as well as the emissivity values and
refractive indices assigned to the faces on each side of the
boundary (
and 
in Equation 13–15, respectively). See User Inputs for Internal Radiation Model for
complete details. For a porous jump sub-model, the inputs are as follows:
Establish a link to a previously defined material dataset (see Defining a Material Dataset for further details), by clicking the Link to a material dataset item.
Link to a material dataset
Then select the name of the relevant material dataset for the current sub-model. For the porous jump sub-model, the dataset should contain numerical values of parameters that are relevant for Equation 8–17.
Next, specify the porous medium thickness (
in Equation 8–17) by clicking the Porous medium
thickness item.
Porous medium thickness
Then enter a New value for the thickness in the panel that opens and click . Although the porous jump model is defined on a surface in 3D or a line in 2D, it corresponds to a porous rigid obstacle that has an actual thickness. When defining this sub-model, it is assumed that the thickness of the membrane is small compared to its other dimensions.