I added a facet created from vertices to close a leak in an imported geometry, I also added a sticking factor. When running the simulation, I don’t see any molecules hitting the surface: no reflections, no transparent passes and no absorption. As suggested in other topics, I checked the direction of the normal vector (and also made the facet two-sided) and the planarity of the facet (0.0). I created a texture downstreams of this facet and see molecules there, I created a transparent facet with texture perpendicular to this facet and see molecules up and downstreams of this facet with about the same rate.
What could possibly be the issue of this problem?
See below for a picture of the geometry. The facet in question is selected.
Hello Carina,
Although you checked the planarity of the facet, it would be good to fix other non-planar facets (since you have the purple warning message on the bottom left).
Causes can be:
You created the facet twice, so there are two identical facets at the same position, and only one is hit
The facet’s structure is not the same as others (probably you didn’t use structures, though)
Is your created facet transparent or opaque? Does it have a texture?
Hello Carina, and thanks for inquiring on the forum.
Just looking at the screenshot you’ve attached I’d say that you have way more details in your model than necessary. For instance, the flange with the holes for the screws, that’s never going to be a “vacuum” volume. If you, as I think, used a CAD program to extract the geometry in STL format, then there are ways to simply select the internal surfaces, i.e. those “seen” by the molecules, and disregard all the rest.
Also, at times it is better to use some of the internal Molflow+ editing features to modify/simplify the geometry, especially when cylindrical structures/geometries are concerned. Marton Ady maybe will be able to point to your attention a document, on the web site, explaining how to extract the internal surfaces only (I can’t do it now, sorry, have a full day today).
Coming to the specifics of your problem, it could be that the molecular traces gets stuck between two facing facets at very short distance from each other (sometimes the same facet with opposite orientations), or 4 facets creating a small “tetrahedral” volume (usually unintended). The way to check this is to start the simulation and click with the mouse on the header of the column “Hits” on the right of the screen, which ranks the facets by number of hits (ascending or descending order): if one molecule gets trapped you’ll see only some facets’ counter increase. You can then highlight those facets and if you zoom in with “Lines” on, you’ll see the raytracing.
The best thing is if you could share with me/us the file, if you don’t wont to post it here you can send it by e-mail… roberto.kersevan@cern.ch.
That’s all I can say with the input you have provided… maybe Marton can elaborate further.
Cheers.
