It is strongly recommended that the VFMSG and VFDIAG files be reviewed after every Viewfactor analysis. Since Viewfactor has been designed to handle most of its own errors, there will be no indication at the computer system level that an error has occurred in Viewfactor. Actual errors are reported in the VFMSG file.

The VFMSG file should be examined to make sure the echoed control data is correct. Then the file should be examined for error messages. If no errors occurred in Viewfactor, the last line of the VFMSG file would be:

Successful Execution Completed.

The following is an example of a VFMSG file from a successful Viewfactor execution with the run control parameter set to 0.

The following is an example of a VFMSG file from an unsuccessful Viewfactor execution. The messages contained in the VFMSG file will be extremely useful for debugging purposes. If you should call one of MSC.Software Corporation support centers with Viewfactor, they will almost certainly ask you about the messages in your VFMSG file.

The numeric diagnostic data is more difficult to review since there are no simple rules for determining acceptable values.

In general, for a closed enclosure, the sums of the viewfactors should not deviate much from one. How much is too much is left to the discretion of the user and will depend on how many surfaces are in the enclosure, how complicated the obstructions in the enclosure are, and on the VFCTL parameters for convergence and integration order $CONVERGE:, $GAUSS_ORDER:, and $AXISYM_SURFACE:.

For an enclosure with symmetric images, if the object with its symmetric images is closed, then sums of viewfactors significantly greater than one indicate that too many symmetric images were created. If the sums are significantly less than one, then this may indicate that not enough symmetric images were created. Here a significant deviation from one is on the order of the inverse of the number of symmetric images.

If the enclosure is open, the sums for surfaces which have a view of the opening should be somewhat less than one. In some simple geometries, you may be able to calculate the view of the opening for some of the surfaces. This number may be compared with the value of one minus the sum for a very good test of the accuracy of the viewfactor analysis.

For larger problems, the statistical information at the end of each enclosure in the VFDIAG file provides a convenient summary of the diagnostic data for that enclosure. The nature of this data was explained in VFDIAG, 101. Your own discretion must be used when evaluating this data.

If you deem the accuracy of the analysis to be inadequate, then this may be remedied by increasing the maximum integration order, reducing the convergence criteria, and refining the finite element mesh in the model. Unfortunately, there are no guarantees here and no one particular method can be counted on to work in every situation.

The following is an example of a VFDIAG file. The enclosure here is the interior of a hollow cube. The faces were modeled with a very coarse mesh and have both triangular and quadrilateral faces. There are 9 surfaces in the model. Since this is a closed enclosure, we expect the sums of the viewfactors should be very close to one. The diagnostic data indicates that for the surfaces the sums are very close to one. However, the sums for the nodal subareas tend to deviate from one by several percent.

You might reduce this error by increasing the integration order, decreasing the convergence criteria, or refining the coarse mesh in the model.