Setting Thermal Radiation Model Parameters

This section deals with the parameters required for solving fluid flows in the presence of thermal radiation. Additional input is required to characterize the optical properties of the boundary surfaces and baffles. Kirchhoff's law is enforced and the optical properties must sum up to one on every surface where they are required.

Boundary Surfaces

The optical properties are defined in the Regions node, for each boundary surface. Boundaries are classified either as Closed, Open, or Inactive. As summarized below, Closed boundaries require specification of both emissivity, , and reflectivity, . In addition, Open boundaries require specification of the radiation temperature, Trad. Inactive boundaries are not directly seen by the radiation and do not require any further specifications.

	Boundary Type						Specify
Boundary Condition	Closed		Open		Inactive						Trad
Inlet: mass flow, stagnation, velocity			X				X		X		X
Outlet: pressure, flow-split			X				X		X		X
Wall	X						X		X
Symmetry plane					X
Cyclic					X

To specify , , and Trad, open the Boundaries node and, for each of the boundary sub-nodes shown under it in the tree, specify appropriate Physics Values for the relevant optical properties as shown below.

Note that where the names of optical properties are preceded by Surface for the Gray Thermal model, they are preceded by Thermal for the Multiband Thermal model and Solar for the Solar model.

Baffle Surfaces

Baffles between two regions where the S2S Radiation Model is active may not be opaque to radiation and require specification of the transmissivity.

To specify , open the Interfaces node and, for each of the in-place interface sub-nodes shown under it in the tree, specify appropriate physics values for the Surface Transmissivity parameter in the Properties window.

Setting the Transmissivity Property for Baffles

Optical Transmissivity

Sets the ratio of transmitted radiant energy over incident radiant energy at the baffle surface.