Error: generate internal fluid mesh on Steady Fluid Flow (CFD) analysis

[Anonymous]

I am getting the error, "The model topology contains edges that prevent it from being used to generate fluid parts." in Simulation Multiphysics 2012, when trying to generate the Internal Fluid shape to look at air flow through a burner.

I am sure this is no easy scenario as the imported CAD model (Inventor) has formed sheet metal parts with holes punched in them to direct and control airflow. I need to learn how to make these run, though. This is the type of scenario we purchased the software for.

I can find no information on this error in the help files or books. The error itself lends no clues; just tells me it doesn't work. The assembly did successfully mesh with the solid meshing check box selected to perform solid meshing during analysis.

Any help would be greatly appreciated.

Attached is an image of a negative I created in Inventor in an attempt to skip the create internal fluid step. I have not been able to successfully mesh this part, yet. It does give you an idea of my geometry, though.

[Joey.X]

As workaround, I would make fluid part(s) in CAD using  subtract boolean operation between parts, then import the fluid part to simulation, this is a much more robust way than generating internal fluid part(s) in simulation.  

[Anonymous]

Thanks for the reply. I am saddled with Inventor 2008 until next year, mid-year. Is this a command in 2012 I do not have or a reference to a concept?

I did get a solid of the negative space, though. I think it was just harder for me than using the command you mention. I derived it and subtracted my assembly. As I mentioned, my resulting solid did not mesh successfully and I did not persue it a lot before writing. Are you suggesting I remain focused on meshing that part?

[Joey.X]

The concept of generating fluid part(s) in simulation is same as the making "negative space" in Inventor, but Inventor is more robust and flexible doing this in my opinion. My suggestion above is for making valid fluid domain and move to meshing phase.

If you want doing fluid flow analysis only, the domain(s) you need are the fluid part(s) only, you can either import all fluid part(s) and solid part(s) into simulation, and then deactivate solid part(s) in simulation or suppress solid part(s) and leave fluid part(s) then import them into simulation. 

If there are multiple parts in fluid domain, one thing important to mention is that surface imprinting needs to be enabled at CAD import option to have conforming mesh between parts. 

Meshing failure is another issue, it often happens for complex geometry, tips include (a) simplify fluid domain (such as clean up small CAD features which have trivial impact to fluid pattern); (b) use full tetrahedral mesh (I am not favor on this since it has other negative issues, but this is a first step to have mesh done and move forward); (c) mesh refinement to ensure enough internal nodes inside narrow channel(s) if you have.

[Anonymous]

I have a solid I created from Inventor. I tried meshing it when I walked out the door for the 4 day weekend. When I returned this morning, I saw it had failed. I will try to put more into it. I'm slated to get a new machine this afternoon that should be a real hot rod compared to mine. I will keep you posted on progress with the messing.

I understand the need to simplify for analysis but in my case I'm looking at airflow through a mixing portion of a burner. I can't crop out all of the details.