Radiation

The radiation load defines radiant exchange between a finite element surface (face) and black body or infinite space.

Radiation in the Nastran environment

In the Nastran environment, you can use the Radiation command to model radiation to space for a heat transfer analysis. The options in the Radiation dialog box generally correspond to the fields on the RADBC bulk data entry. However, Nastran requires a number of different bulk data entries, such as RADBC, RADM, and SPOINT, to fully define radiation. The software automatically creates these necessary bulk data entries when you export or solve your model.

Specifically, it creates:

• A RADBC bulk data entry.

• An SPOINT and SPC entryWhen you define the Ambient Temperature value in the Radiation dialog box, the software automatically creates an SPOINT entry. the software assigns the ID field on the SPOINT ID entry to the FAMB field in the RADBC entry. The software then uses an SPC entry to constrain the temperature value at that location.

• RADM or RADMT, and TABLEM1 entries which provide the reference between the RADMID field and the material associated with the CHBDYi elements..

• The TABS and SIGMA parameters, which define the absolute temperature scale and the Stefan-Boltzmann constant

Additionally, in Nastran, surface elements (CHBDYE, CHBDYG, or CHBDYP) provide the geometric connection between the structural elements in the mesh and the applied radiation. Because you cannot create Nastran surface elements directly in NX, NX automatically creates them for you when you export or solve. In a SOL 153 or 159 analysis, you can use the Geometric Surface Element Form option on the General tab of the Solution dialog box to control the type of surface elements that the software automatically creates.

Radiation in the Abaqus environment

In the Abaqus environment, the options in the Radiation dialog box correspond to the parameters for the *RADIATE keyword. In NX, you can use the Radiation dialog box to define element-based radiation within an Abaqus heat transfer analysis. You must specify the ambient temperature value, Θ0, and the emissivity of the surface, ε.

In Abaqus, you must use *RADIATE keyword in conjunction with the *PHYSICAL CONSTANTS keyword to fully define the Stefan Boltzmann constant, as well as values for absolute zero and the universal gas constant. In NX, when you create a Radiation load, NX creates both the *RADIATE and *PHYSICAL CONSTANTS keywords in your input file. For example:

*PHYSICAL CONSTANT, ABSOLUTE ZERO=-4.596700E+02, STEFAN BOLTZMANN= 3.083640E-11, UNIVERSAL GAS CONSTANT= 7.159585E+03**%**%*RADIATE        57, R3,  1.000000E+03, 8.000000E-01        69, R4,  1.000000E+03, 8.000000E-01        91, R1,  1.000000E+03, 8.000000E-01

Radiation in the ANSYS environment

In the ANSYS environment, the options in the Radiation dialog box correspond to the SFE,,RAD command. You can use the Radiation command to analyze ambient radiation heat transfer to space at a constant temperature. In the Radiation dialog box, you can specify both the surface emissivity and the ambient temperature.

Where do I find it?

Application	Pre/Post
Prerequisite	An active Simulation file with Nastran, Abaqus, or ANSYS as the specified solver and Thermal as the specified Analysis Type
Command Finder	Radiation
Simulation Navigator	Right-click Loads→New Load→Radiation

Quick links

Command reference

Pre/Post video examples

Bulk Entry Descriptions

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Radiation, Simcenter 3D 2021.1 Series

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