Nonsymmetric result from symmetric flow and geometry?

jh1998 · August 27, 2022, 14:24

Hello all,

I have a fairly good experience in commercial CFD solvers (Fluent and the likes) but wanted to try OPENFOAM. I started with a simple geometry and flow to get used to the openfoam file structure but received an unexpected result.

The flow seems to stick to one side of the nozzle after a certain number iterations. I presumed it was due to a numerical error that accumulated over time, but running it several times produced the same result.

This does not seem to happen when the restricted section in the middle is wider. I run the simulation using icoFoam (following blockMesh)

P.S. only one cell is in the z-direction. fvSchemes and fvSolution are directly from icoFoam tutorials.

Files and velocity field screenshot are attached below.

Any ideas would be appreciated. Thank you.

Alczem · September 8, 2022, 03:10

Hey

I am not 100% sure about this, but I simulated venturi nozzles a while back and had similar behaviors. From what I can remember, which is not a lot, at certain reynolds number (or some other adimensional number), the flow is expected to deviate like your picture. I guess that if you tried in a transient simulation, the flow might oscillate and not stick to only one side.

(I might be totally wrong! Check some scientific papers, I know there are some talking about this)

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September 8, 2022, 03:10		#2
Alczem Senior Member Join Date: Dec 2021 Posts: 207 Rep Power: 5	Hey I am not 100% sure about this, but I simulated venturi nozzles a while back and had similar behaviors. From what I can remember, which is not a lot, at certain reynolds number (or some other adimensional number), the flow is expected to deviate like your picture. I guess that if you tried in a transient simulation, the flow might oscillate and not stick to only one side. (I might be totally wrong! Check some scientific papers, I know there are some talking about this)