Working with Solid Materials

To Assign a Solid Material

2. Open the Material quick edit dialog. There are several methods:
   • Left click on the part, and click the Edit icon on the context toolbar.
   • Right click on the part, and click Edit...
   • Right click on the part name under the Materials branch of the Design Study bar, and click Edit....
   • Click Edit in the Materials context panel.
3. Select one or more parts.
4. Select the database from the Material DB Name menu.
5. Select Solid from the Type menu.
6. Select the material from the Name menu.
7. Click Apply.

Example of Solid Material Assignment

To Create a Solid Material

Solid Materials are defined using the Solid Material Editor.

1. To open the Material Editor, click Material Editor on the Materials context panel.
2. Click the List button.
3. Right click on a custom database, and select New material. Select Solid. Specify a Name.
4. Click the property button that is to be defined.
5. For each property: Select the Variation method, enter the appropriate value and units, and click Apply.
6. Optionally, click Save.
7. Click OK. The new material is available when the Materials quick edit dialog is opened.

The Default material database contains at least one instance of every material type. A convenient way to create a new material is to use a Default material as an example. Because these materials are read-only, use the Material Editor to copy the original into a custom database, and modify the copy. For more about creating a material from an existing material...

Solid Properties

There are four basic properties that are necessary to define a solid for use with Autodesk Simulation CFD. Most of these properties can vary with temperature, pressure or scalar, in several different variation methods. These properties and methods are listed in the following table:

Property	Variational Methods
Conductivity -- the same value for thermal conductivity can be used for all three directions, or each component can be different.	Constant, Polynomial, Inverse Polynomial, Piecewise Linear. Y and Z directions also have: Same as X-Dir.
Density -- only needed for transient analyses.	Constant, Polynomial, Inverse Polynomial, Piecewise Linear.
Specific Heat -- only needed for transient analyses.	Constant, Polynomial, Inverse Polynomial, Piecewise Linear.
Emissivity -- useful for radiation analyses. The emissivity specified on a solid will override the value assigned to contacting fluid.	Constant, Piecewise Linear variation with temperature (useful for spectral radiation analyses.)
Transmissivity -- useful for radiation analyses; see note below	Constant, Piecewise Linear variation with temperature
Electrical Resistivity -- only needed for Joule heating analyses.	Constant, Polynomial, Inverse Polynomial, Piecewise Linear (varies with temperature).
Wall Roughness -- useful for applying variable roughness height to include effects of friction	Constant. Please see section about Wall Roughness.

Transmissivity

Transmissivity is a measure of how much radiative energy can pass through an object. A value of 1 indicates that the object is completely transparent, and that radiative energy can pass completely through it. A value of 0 means that the object is opaque. The permissible range of transmissivity values is between 0 and 1.

Two variation methods are available for transmissivity: Constant and as a Piecewise Linear table varying with temperature. Transmissivity is a unitless parameter. The default value is 0.

The sum of Transmissivity and Emissivity must be less than or equal to 1.

If the sum of these two values exceeds 1, an error message will be displayed when the analysis is started.

Transmissivity can only be assigned to solids. The radiation model considers fluids to be non-participating, so it is not possible to simulate radiative heat transfer through dark or “muddy” fluids.

To simulate a transparent object completely immersed within a fluid:

• Model the object as a solid and mesh it (it cannot be a suppressed part).
• Assign a transmissivity value between 0 and 1 to the solid material to allow radiation to pass through the object.

To simulate radiative heat exchange between a transparent solid and the environment, such as a window:

• Model the window as a solid in the model.
• Assign a transmissivity value to the material for that solid.
• Assign a Transparent boundary condition to that surface. This boundary condition includes a background temperature

Surface parts cannot be used to simulate transparent media. A non-zero value of transmissivity applied to surface parts will be ignored. Likewise, non-zero values of transparency assigned to moving solids are ignored--transparency is not supported for moving solids or within rotating regions.

Note: Absorption of radiation energy by transparent solids is not included in the radiation model.

For more about Transmissivity in Radiation Studies

Electrical Resistivity

The resistance per area multiplied by the length of the device. A value for resistivity is required for any solid that is heated by the Joule effect.

The relationship between resistivity and resistance is:

• R = resistance (ohms)
• r = resistivity (ohms-length unit)
• L = length of the device
• A = cross sectional area

For more about Joule Heating