The Viewfactor boundary condition data is output from Patran in the neutral file packet 19s. The neutral file is read by Patran Thermal’s PATQ and translated into the Viewfactor input file VFINDAT. The VFINDAT file is described in detail in Chapter 9. The relationship of data in the neutral file to data in the VFINDAT file is described in general terms.

The VFINDAT file begins with title data for the problem, followed by data about the size of the problem. Next is symmetry data which is discussed in Compatibility Requirements for Model and VFAC Templates, 65. All of the nodes in the Patran model are then copied to the VFINDAT file, including their IDs and coordinates.

The surfaces with VFAC boundary conditions are then grouped into their respective enclosures and put out to the VFINDAT file grouped by enclosure. Some of the data in the VFAC record is copied directly. This data is the enclosure ID, the user function ID or TID, the participating media node or MEDNOD, the ambient node or AMBNOD, and the convex surface ID or CNVSID. The nonobstruction flag is translated to 0 or 1 and copied. The element ID with which each surface is associated is in the packet 19 and also copied to VFINDAT.

The VFINDAT file also requires other information about the surface. This is developed by PATQ from data about the model from other parts of the neutral file. This data includes information about the shape of the surface, the order of interpolation functions needed to describe the surface, the number of nodes associated with the surface, an ID for the surface, an identification of the element face represented by this surface, the node IDs associated with this surface, and possibly some other data associated with the surface.