I am a new Freecad/CfdOF user.
First of all, thanks for all of the effort you and your co-workers have put into the FreeCad/CfdOF software. It is unbelievable to me that this resource is available at no cost. I have been looking for something like this for a while.
I work in the oil and gas industry and have done a lot of work on separation equipment, ie. gas-liquid and 3-phase (gas-oil-water). There are some aspects to separator design/performance that I have been unable to quantify due to lack of access to CFD software. Now I have it thanks to FreeCad/CfdOF. I was hoping there would be a “sub-forum” dedicated to CFD for separator design but I haven’t found this if there is. Actually, surprisingly little on separators at all.
Below (attached) is a sketch of my gas-liquid separator.
At this point I am not trying to model both the gas and liquid phases (maybe try this down the road), just trying to visualize the gas flow thru the separator. A key issue in separator design is velocity distribution thru the equipment. In a vessel like this, gas-liquid separation performance is highly dependent on gas velocity at various locations from the inlet feed pipe thru to the outlet.
So far, I have had the most luck putting this together using “primitives” I guess you call them, from the Part workbench. Lot’s of trial and error, watching Youtube videos, tutorials, etc. I had originally started with the Part Design WB after watching Pawel Lojek’s heat exchanger tutorial. I struggled with this for quite a while. The Part WB has worked better for me.
Of course this is a big subject and I’m happy to peck away with trial and error and scouring the internet. I just wanted to clear up a couple of things and avoid wasting too much time:
1. Am I on the right track based on what I’ve explained that I’m trying to do ?
- The Part WB is fine for constructing my geometry ?
2. What about the meshing tool ? I’ve watched Pawel’s tutorial and Michael Hindley’s tutorial https://www.youtube.com/watch?v=8A9GewANqh8 and they both used cfmesh, so this is what I used. My first simulation (base case) did not have the inlet diverter plate and seemed to run fine. Then I put in the inlet diverter plate (shown in sketch below) and when I reran the simulation I was surprised to see that the results in Paraview looked like the inlet device wasn’t even there ! Then I found this post of yours (below) which says “cfMesh doesn’t support baffles and internal regions” ! I guess this is my problem ? Also, I have tried to model my mist extractor as a “porous” zone. I think I did it right, but again, based on your comment, I’m wondering if cfMesh is ignoring this also ? I think I’ve got the Darcy-Forchheimer coefficients figured out for defining the mesh pad/porous zone. Can you point me to any more info on this area ? – I couldn’t find much on the forum, tutorials, etc. I have got some info on this subject from a couple of other sources though.
3. When I delete the CFD Analysis container and try to redo things with snappyhexmesh or gmesh I get error messages when I try to run the solver. In your note below you mention that there are tutorials for snappy and gmsh and that the geometry setup is different between these (and probably cfmesh as well ?). Can you point me to these tutorials ? Maybe I need to rebuild the geometry from scratch for these different meshers but if there are some tricks, would be good to know.
4. In the Part WB, are the “parts” solids or hollow ? Probably a dumb question but in some tutorials they are treated as solids in others, eg. Michael Hindley’s tutorial, they are “hollow” allowing flow thru them. Maybe for CFD applications they are treated as “hollow” by defining inlet, outlet and walls ?? I’ve seen tutorials where “pipe” has been made by using 2 cylinders then performing a cut, etc. Hindley’s video didn’t do this and I didn’t either. A bit confusing.
5. Are there any good CfdOF tutorials out there on separation equipment that you know of ?
Bottom line:
1. Is the Part WB ok for what I am trying to do ? CFD with vessel internals including a porous zone.
2. Which mesher should I be using ?
3. Guidelines for acceptable “residuals” for the solver and guidelines for achieving efficient (with acceptable accuracy) convergence ?
I am running the software on a Lenovo Carbon X1 – nothing fancy but seems to be working OK.
Thanks very much for any help.
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