Viewfactor provides support for finite element analysis of thermal radiation phenomena in the Patran Thermal module by providing the viewfactors and thermal network resistors between thermally radiating surfaces.

Presently, diffuse surfaces (surfaces whose radiative properties are independent of direction) are supported. The surface properties are permitted to have spectral dependence in the form of an arbitrary number of piecewise gray wavebands. Thus, the Viewfactor program provides a practical means of modeling diffuse spectral surfaces.

Viewfactor provides support for radiation interchange between the following element faces:

These elements faces represent all of the elements faces usually needed to model thermally radiating surfaces.

Viewfactor provides support for multiple symmetries in the model. For 3-D geometries, Viewfactor provides support for reflection across a plane and rotation of “n” times by “x” degrees about an arbitrary axis. For 2-D XY geometries, it provides for reflections across a line in the XY plane and rotation of “n” times by “x” degrees about an arbitrary axis perpendicular to the XY plane. For 2-D axisymmetric geometries, it provides for reflections across a line perpendicular to the Z-axis and in the RZ plane. Four separate symmetry objects and symmetry operations may be combined in the same model. Viewfactor does not check for the validity of any symmetry operations. These symmetry operators provide a convenient way to deal with thermal models which are symmetric in all respects except for the radiation component of the problem.

Viewfactor is closely coupled with Patran and Patran Thermal and is specifically designed to work well with them. Patran is responsible for the generation of the thermal model and boundary conditions. The Patran Thermal PATQ interface program handles all data translation between the Patran neutral file and the Viewfactor input file. Viewfactor reads the input file and the Patran Thermal template file and then generates a file containing radiation resistors for QTRAN analysis processing.

Viewfactor provides support for all of the commonly used model coordinate systems. These are 2-D XY, 2-D RZ axisymmetric, and 3-D XYZ coordinate frames.

Coupled with the capabilities in the Patran Thermal module Viewfactor provides support for time and temperature-dependent material properties such as surface emissivities and participating media transmissivities.

Viewfactor provides for efficient obstruction checking at the element level.

Multiple enclosures are modeled in both Viewfactor and Patran Thermal. This feature, along with the multiple wavebands for spectral surfaces, allows for the modeling of phenomenon such as partially transmitting windows.

No fixed problem size limit exists for Viewfactor. Memory for the particular model being analyzed is allocated during run time. Problem size is limited only by available virtual memory, available CPU resources, and storage space for the output data. Core memory requirements are linear functions of the model size, not higher order functions as is true for some viewfactor analysis programs.

Through use of the Patran Thermal template file, Viewfactor provides support for optically thin participating media.

The geometric calculations involved in determining obstructions and viewfactors are saved as an intermediate result and can be reused with different material properties in the same model. These CPU intensive calculations need not be repeated when material properties change.

Viewfactor checks for convergence of its numerical integration algorithms and increases or decreases the integration order as appropriate. This provides excellent performance as measured by the product of accuracy and speed.

Diagnostic data is provided to aid in verifying the accuracy of an analysis.

Viewfactor provides support for radiation to an ambient or space environment node.

Convex surfaces may be flagged to help reduce execution time.

Nonobstructing surfaces may be flagged in order to reduce the time required to check for obstructed views.