Need help sculpting complex geometry

[Anonymous]

Hi,

I'm trying to do a CFD analysis for an FSAE car that we designed, the problem is I can't fix the geometry in order to mesh it. I've received the suggestions to make the geometry solid and watertight. I've made the geometry solid, but it's not watertight yet. Any help or suggestions are really appreciated.

I've uploaded the link to the file below.

Cheers!

Akul.

[TrippyLighting]

If its a solid its water tight. All your bodies are solid bodies.

I could imagine that the CFD software has a problem with meshing all these thin walled structures though.

[Anonymous]

How do you suggest i fix this issue?

[TrippyLighting]

Talk to whoever makes the CFD software you are using and perhaps post on the relevant CFD forum.

If that requires to modify the geometry, then come back here.

In that case, also share a model with a proper timeline 😉

[laughingcreek]

When otherwise separate solids in fusion share and edge, fusion is happy to call it a single body.  see pic below.  this shows 2 cubes that share an edge.  fusion thinks of them as a single body.

when a body like this i exported as a mesh, most algorithms will be tripped up by this condition.  it will think it's non-manifold, not water tight, or a number of other things depending on the program.

I exported your model as a mesh and used mesh mixer to analysis it.  then went to the location on the model indicating a problem and found the condition described above.  see screen cast.

The fix for this particular problem is to make sure these areas meet with some definitive volume, not just at an edge.  or back the face away so there is no contact.

that will fix this specific problem, but looking at your model you may encounter other issues as well.

[Anonymous]

Hi,

I have fixed the gap between the body as you suggested, but I am still unable to mesh it. Unfortunately, I can not contact the person who made the design as he is unavailable. I am running out of options.

What do you suggest I do now?

[laughingcreek]

Is the problem not being able to create a mesh, or the CFD software not accepting the mesh you create from fusion?  What CFD software/service are you trying to use?

[laughingcreek]

Another possibility is that the CFD software doesn't like mesh files that have multiple "shells".  while sometimes desirable when done with purpose, multiple shells can also get defined inadvertently with from weird geometry.  Here's another screen cast using mesh mixer to run a separate shells operation, revealing that there is some weirdness in the cylinders on top of the fairing.  looks lie there may have been some threads in there at onetime maybe. I would try saving out the primary "shell" and see if that runs ok.

[Anonymous]

I'm having trouble creating a mesh in the cfd software. I even tried to
create a mesh in fusion and import it in the software, but I have problem
in creating the name selections for input and output. The software I use is
fluent, and the cloud service simscale.

Regards,
Akul Bhatt

[TrippyLighting]

@Anonymous I've suggested this before in this thread but I am not sure you've followed my advise.

Is there a Forum for that CFD software where you can get advise on how to proceed and what the problem might be ?

In my opinion you are addressing this question to the wrong crowd. I don't use CFD software but have some working knowledge of the basic underpinnings of FEM software. The meshing algorithms in CFD software work completely different from those employed in creating .stl meshes and are much more sophisticated than the primitive .stl algorithms. Most FEM software (which CFD is a subset of) meshes solid geometry (BRep) into tetrahedral meshes. Netgen is one source an interesting to play with

Before you can start fixing geometry you need to get some understanding of what input the CFD software is happy with. It is not unusual for FEM stress analysis having to simplify geometry and in fact that exactly is the entire purpose of the "Simplify" workspace in Fusion 360's simulation tools set.

Currently you are just throwing what would appear to me like quite a hack of geometry at some tool. Even if meshing in the CFD would succeed I seriously doubt you get meaningful results out of it.

Garbage in usually results in garbage out!

P.S. The title to this thread is also very misleading. Your set of problems have absolutely noting to do with sculpting in any software.