Purpose

Viewfactor has fixed memory requirements for about 820 K bytes on the VAX 8600. In addition to this memory, Viewfactor calculates the amount of memory needed based on the number of nodes in the model, number of surfaces in the current enclosure, dimensionality of the model, number of symmetric images and number and size of the VFAC templates.

The memory requirement for calculating viewfactors also depends on the number of potentially obstructing surfaces in the enclosure and on a few other parameters in a complicated manner. Therefore, we will only give an upper bound on the memory requirement. The memory required, in bytes, to calculate viewfactors will be less than approximately the value of the expression:

Parameter	Description
DIM	Dimensionality of the model, 2 for 2-D XY and RZ axisymmetric models, 3 for 3-D XYZ models.
SYMMUL	Number of images of the model after all symmetry operators have been applied to the model, includes the original image of the model.
NSURF	Number of surfaces in the enclosure for which viewfactors are currently being calculated.
NNODE	Number of nodes in the model. The memory requirement for converting viewfactors into Patran Thermal radiation resistors depends on the number of resistors to be created in an enclosure. The virtual memory system will request enough memory to hold all of the resistors created in an enclosure before any of the resistors have been merged. Since the number of resistors created depends on the viewfactors calculated, we do not know in advance how much memory will be required. Viewfactor was designed to access as much memory as needed through the computer’s virtual memory system. Viewfactor will handle as large of problem as there is virtual memory available for it to use. Also note that the memory requirements are linear with respect to the number of surfaces in each enclosure and also linear with respect to the number of nodes in the model. Thus, in general, computer memory will not be the limiting resource for viewfactor analysis with Viewfactor. However, a large amount of memory may be needed for sorting and merging the resistors made after the viewfactor calculations.
NVFAC	Number of VFAC templates found in the TEMPLATEDAT file.
TOTBND	total number of bands, or VFAC template data records (not header record found in the TEMPLATEDAT file.
NUID	Number of distinct UIDs (User IDs) in the current enclosure.

Parameter

Description

DIM

Dimensionality of the model, 2 for 2-D XY and RZ axisymmetric models, 3 for 3-D XYZ models.

SYMMUL

Number of images of the model after all symmetry operators have been applied to the model, includes the original image of the model.

NSURF

Number of surfaces in the enclosure for which viewfactors are currently being calculated.

NNODE

Number of nodes in the model.

The memory requirement for converting viewfactors into Patran Thermal radiation resistors depends on the number of resistors to be created in an enclosure. The virtual memory system will request enough memory to hold all of the resistors created in an enclosure before any of the resistors have been merged. Since the number of resistors created depends on the viewfactors calculated, we do not know in advance how much memory will be required.

Viewfactor was designed to access as much memory as needed through the computer’s virtual memory system. Viewfactor will handle as large of problem as there is virtual memory available for it to use. Also note that the memory requirements are linear with respect to the number of surfaces in each enclosure and also linear with respect to the number of nodes in the model. Thus, in general, computer memory will not be the limiting resource for viewfactor analysis with Viewfactor. However, a large amount of memory may be needed for sorting and merging the resistors made after the viewfactor calculations.

NVFAC

Number of VFAC templates found in the TEMPLATEDAT file.

TOTBND

total number of bands, or VFAC template data records (not header record found in the TEMPLATEDAT file.

NUID

Number of distinct UIDs (User IDs) in the current enclosure.

Viewfactor was designed to access as much memory as needed through the computer‘s virtual memory; it will handle as large of problem as there is virtual memory available for it to use. Also note that the memory requirements are linear with respect to the number of surfaces in each enclosure and with respect to the number of nodes in the model. Thus, in general, computer memory will not be the limiting resource for viewfactor analysis with Viewfactor.