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nextfoam / baram

CFD for Everyone
https://baramcfd.org/
GNU General Public License v3.0
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Specify a pRefCell value other than 0 #121

Open CFDEnthusiast opened 2 months ago

CFDEnthusiast commented 2 months ago

Hi there,

I'm duplicating a ~20-year-old simulation undertaken with Fluent, in BaramFlow (24.3.3). However, I can't seem to change the pRefCell value to something other than 0, since in my example Cell ID = 0 does not have a gauge pressure of zero.

Is there a way to change the Cell ID for pRefCell? Perhaps on the Reference Values tab? I gather this approach (or similar) may have been a feature in a previous version, but I have not tested all previous versions.

I have tested manually changing the fvSolution file, but it looks like that file is overwritten when the simulation is started from within the GUI. I've Also tried running it from the command line, but this approach presented a new set of issues.

Any advice on this would be appreciated.

Thanks!!

jiban commented 2 months ago

Hello, BARAM does not have UI to configure pRefCell for now. It is fixed as you have seen. ( pRefCell 0; ) By the way, in general, pRefCell affects only the convergence of the calculation, and pRefCell 0; setting has no problem in most cases. Could you tell me more about your case so that I can think of proper fix for it? Thank you.

Best regards, Jake

CFDEnthusiast commented 2 months ago

Hi Jake Thanks for the response and considering my query.

The case is as follows:

Setup shown below (9 seconds simulated) (Pink dot shows pRefCell location - Cell ID =0 taken from Paraview)

My concern is that I still have mass flow coming into the domain at the outlets, even with the free surface higher than the outlet level. I have tested the simulation with negative pressures on the outlet, which resulted in mass outflow as expected, but it seems that the free surface is moving up and down a bit while searching for that steady location that results in mass in = mass out.

It could be that the simulation has not run long enough, but I was also starting to wonder about the impact of the location of pRefCell.

PS_Setup

Best regards

kdg5424 commented 2 months ago

Hello @CFDEnthusiast. This is Donggyu from NEXTFOAM.

The pRefCell affects the very begging of the simulation like the first step in simulation. And the process which is searching for the steady location of the free surface is very natural. It just happenes because your case is transient case. The free surface moves up and down for searching the balance between the inlet mass flow and outlet mass flow. Overall, you mentioned, the simulation has not run long enough.

And even for the real situation, there are the similar cases. In reality, the free surface might move up and down while searching the balance between inlet mass flow and outlet massflow.

And the free surface of your case looks very nice. I think you generated mesh very well.

Best regards

Donggyu Kim