Hi All,
I'm asking for some
Hi All,
I'm asking for some advices about a CFD calculation I would like to perform. I need to calculate the flow coefficients of the intake valve of a pent-roof spark-ignition engine. I created the mesh with commercial mesh generator and I converted it correctly. I defined three patches: - walls: they are the cylinder walls, the port walls, the valve walls - inlet: where the air comes in - outlet: where the air goes out Questions: 1) Which solver can I use? I was thinking about sonicTurbFoam. But I am not sure it can be the right choiche because the pressure difference experimentally imposed is usually about 0.1 bar. May I consider the fluid as incompressible? 2) If I use a sonicTurbFoam, what boundary conditions should I impose for pressure and velocity at inlet and outlet patches? I was thinking: inlet: fixedValue for velocity and zeroGradient for pressure outlet: zeroGradient for velocity and fixedValue for pressure (set to the experimental value of 0.9 bar). with this setup I get oscillations in the pressure field and I don't reach a steady solution as I would. How can I get rid of these oscillations? Should I use pressureTransmissive instead for the pressure boundary condition for the outlet? I really appreciate any suggestion/comments and would like to know if someone else foam-user has experiences about flow-coefficients estimation for engine valves. Thanks a lot. Regards. Tommaso |
grazie tommaso..
grazie tommaso..
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Unless your flow is transonic,
Unless your flow is transonic, I would use rhoTurbFoam. And yes, a pressureTransmissive outlet is necessary to prevent wave reflection. (Please let me know how it [pressureTransmissive] performs, the last time I tried to use it I ran into some problems, which I didnt have time to investigate.)
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Ah finally Tommaso I can help
Ah finally Tommaso I can help you!
I use the pressureTransmissive alot, it's very efficient at damping out oscillating waves in a wedge, especially if there's a very big pressure wave coming from a small nozzle into the wedge. Nevertheless, remember to that lInf is a compromise between how reflective you can allow it to be and how important it is for the pressure to remain at pInf. A little trial and error is appropriate I think. BTW How high is your estimated Mach number? /Fabian |
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