Hello all,
I’m working on this model to obtain a heat transfer and flux diagram but I keep getting this non positive jacobian error. In the last simulation I ran I was able to visualize the result of the failed model and the error is concentrated on few nodes of the geometry. Is there a way to avoid this error or at least to filter out of the simulation these nodes? the forum says I can’t upload the file since I’m a new user, hence I hope a screenshot is enough.
Thanks!
If you want to delete those individual elements from the mesh, you could convert the element set to part and then delete it but it may not be a good idea since those elements may play important role in your model and you probably don’t want to have gaps in it. Unless those are just some artifacts accidentally created during meshing. How was this mesh generated ? Was it imported from other software ? What is the source of the geometry ?
You can use some hosting website like Google Drive, Dropbox or WeTransfer and paste the link here to share the model.
I will upload it now, thanks for the suggestion: WeTransfer - Send Large Files & Share Photos Online - Up to 2GB Free
I modeled it on rhino and grasshopper and then exported the geometry on prepomax as an stl file. The mesh was created on prepomax but I can’t see those same spikes in the meshed model before starting the simulation.
It might be better to export to STEP file, it should be possible in Rhino.
The geometry of that porous structure is really complex and should be meshed carefully. Reducing the size of elements may help.
Pay attention to very thin ribs like this:
I tried to export the geometry from rhino and this error shows up:
I don’t know Rhino but you would probably have to convert this geometry (surface mesh from a 3D scan?) to NURBS. Perhaps this software could also fix the problematic regions that can be causing the negative jacobian error. After exporting from Rhino you can pretty much only try reducing the element size to fit more elements in those narrow regions.
the mesh results shown using automatic tetrahedral of CAD files, you can try to refined a mesh from maximum element size at parameter menus.
sometimes, even for simple geometry of thin solid raised to similar problems.
