FloWorks question

[BoomerSooner7]

Hello all,

Attached is a simplified model of a design I'm working on and I'm trying to find the pressure drop across the piston with the .003" wall clearance. My computer crashes everytime I try to run the calculation due to lack of memory because of the small mesh size I'm assuming. Are there any settings I can tweak or anything I can do short of buying a new computer to help the simulation along?

thanks in advance

 

[kellnerp]

Just because a CAE program allows you to do something doesn't mean it is the best approach. Your job is to figure out how to do this accurately with the least number of cells.

Perhaps a hand calc is in order for starters. This type of problem should be solved by somebody already.

Use axisymmetric. Obviously the flow past the piston is nowhere near the flow into the cylinder. Why not model just the piston to cylinder clearance as 2D axisymmetric?

Thanks for including an illustrative picture.

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[BoomerSooner7]

Thanks for the reply.

What the picture doesn't show is a drain port on the backside of the piston back to a tank at atmospheric pressure, so the flow out HAS to equal flow in to maintain conservation of energy. I've done the pressure drop across the piston in different programs treating the surface area difference between the piston diameter and cylinder wall as an orifice, this is a simple practice assuming you model the orifice correctly. What I am curious about is how reliable the results are because there are different k factors or Cv values to use depending on the geometry of the orifice, based on the "abruptance" of flow. Since this is different geometry than a typical orifice this is the only way I know to get a verification of results.

 

[kellnerp]

What Reynolds number did you calculate for the flow?

What is the velocity of the flow past the piston to the velocity of the piston?

Again, why not solve this as a 2D axisymmetric problem.

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[BoomerSooner7]

Is there a way to set this up as a 2D axissymetric problem in FloWorks?

 

[kellnerp]

Not sure. I think they put that functionality in after I used it. Check the documentation. I know you can in CFDesign.



TOP
CSWP, BSSE

http://www.engtran.com

http://www.niswug.org

"Node news is good news."