Setting view factor parameters

On the View factors tab in the Numerical parameters dialog you determine the precision of the view factors and the threshold for the Gebhardt matrix.

  1. Select Computation > Numerical parameters.

    The dialog will open with the View factors tab active:

    View factors tab in Numerical parameters dialog 

    Figure 10. View factors tab in Numerical parameters dialog

  2. Change the default values only, if necessary, because they usually produce a reasonable result.

    Overwrite the precision value, if appropriate.

  3. If the threshold for Gebhardt matrix is > 0, only Gebhardt factors above a certain value are taken into account. For more information on the Gebhardt matrix see the PhD thesis by M. Kurz 1998, p. 71.

    Overwrite the threshold value.

  4. Click on Apply to apply the changes, but leave the dialog open.

  5. Select Computation > Compute View Factors.

  6. Wait until the computation is finished and then:

    Select Computation > Show Solver Information > Rowsums.

    The view factor graph, the rowsum minimum (recommended: 0.98) and the rowsum maximum (recommended: 1.02) will be displayed.

    In the following example the view factors should be improved:

    Row sums of view factors 

    Figure 11. Row sums of view factors

    The view factors are satisfying, if the difference between minimum and maximum is acceptable for you. Based on our experience we suggest to accept deviations which are smaller than about 10%.

  7. Warning

    Renormation is not reversible. You can renorm the Γ matrix only once!

    As soon as you checked the renormation button, it will be inactive forever!

    Be definitely sure that the quality of the view factors is sufficient, before you check the renormation button.

    Go back to the view factors tab in the Numerical parameters dialog and check the Renormation box.

    The Gebhardt matrix will be renormed and this file can be used as input file for future computations based on this mesh.

Related Dialogs

View factors