The input parameters and options for the tool are described below. When the input form has been completed, pressing the button will start the calculation and bring up the "Results" page.

Input parameters

• Geometry file
• Area limit (relative or absolute) for Delaunay triangulation
• Integration tolerance

The geometry file is a collection of objects (max. 10) with surfaces (in total max. 60) between which view factors are computed. The user can upload his own geometry file, create a new one with the SPENVIS Java Geometry Generation Tool (JGDT) or select one of the predefined geometry files (Shapiro(1983), Micro VCM, ASTM E 1559 and a Cube) which are described in the background help pages. The input geometry file should be in the same format as this sample input file.

When using the JGDT and having created a geometry, the geometry file is exported with Export NML, as shown on the screenshot:

Figure 1. Export of geometry file created with JGDT.

The accuracy (and computing time) of the view factor is controlled by the minimum area for a Delaunay triangle and an integration tolerance ε.
In order to compute the view factor, each surface is divided into triangles using the Delaunay algorithm. The triangulation is ended when a minimum triangle area is reached. The user has the option to set this minimum by an absolute (in m²) or a relative (to the area of the surface) value.
The accuracy of the viewfactor can be further improved by dividing the triangles in subtriangles or by dividing the edges of the triangles in subsegments. In both cases the number of subdivisions is controlled by a tolerance factor that defines the maximum allowed difference between computed successive values of the view factor. The user can set the value of this integration tolerance.
We remark here, that in order to limit the computational time, a limit is set on the number of subdivisions which implies that it can happen that the requested tolerance is never reached.
Finally we don't use the reciprocity relation (A_iF_ij=A_jF_ji), but calculate F_ij and F_ji separately.

Results

The report file spenvis_vfp.html contains the input parameters and a summary output table.

The output file spenvis_vfo.txt contains the view factors between the different surfaces and the area of the surface in m². The data are used by CONTAM to compute the contamination.

The output file spenvis_vfv.x3d displays the geometry file.