Divergence for simple geometry room

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Yvan Fournier
Posts: 4070
Joined: Mon Feb 20, 2012 3:25 pm

Re: Divergence for simple geometry room

Post by Yvan Fournier »

Hello,

Sorry, I did not have the time to test the case yet. I'll let you know as soon as I run it.

Best regards,

Yvan
Tsubasa
Posts: 175
Joined: Fri Nov 20, 2020 4:09 am

Re: Divergence for simple geometry room

Post by Tsubasa »

Hello,

Ok, Thanks.
Even in steady simulation, divergence problem happned.

Best regards,
Hamada
Yvan Fournier
Posts: 4070
Joined: Mon Feb 20, 2012 3:25 pm

Re: Divergence for simple geometry room

Post by Yvan Fournier »

Hello,

Changing the outlet to "imposed pressure outlet" alone was not sufficient, but switching to least-squares gradient reconstruction with full extended neighborhood, I can run 500 iterations just fine (tested with v7.0).

Best regards,

Yvan
Tsubasa
Posts: 175
Joined: Fri Nov 20, 2020 4:09 am

Re: Divergence for simple geometry room

Post by Tsubasa »

Hello,

Thank you for the test.

I am grad to hear that steady simulation can be done by steady simulation.
Also how about unsteady case?

Do you think it can be done with Ver.6?
Finally I want to do pressure-driven flow by SRC code, but now the simulation has a divergenec problem with Ver.6.

Best regards,
Tsubasa
Yvan Fournier
Posts: 4070
Joined: Mon Feb 20, 2012 3:25 pm

Re: Divergence for simple geometry room

Post by Yvan Fournier »

Hello,

I actually ran the test for an unsteady flow (as your setup.xml was set for unsteady, constant time step).

This should probably also work in v6.0, though I recommend upgrading to v7.0.

Pressure driven flow should work, but may be a bit more sensitive. Increasing the pressure difference progressively (using a ramp type function) rather than all at once might help.

Best regards,

Yvan
Tsubasa
Posts: 175
Joined: Fri Nov 20, 2020 4:09 am

Re: Divergence for simple geometry room

Post by Tsubasa »

Hello,

Thanks a lot.

At first, I will build Ver.7 and do the test with it.

Best regards,
Tsubasa
Tsubasa
Posts: 175
Joined: Fri Nov 20, 2020 4:09 am

Re: Divergence for simple geometry room

Post by Tsubasa »

Hello Yvan,

In the previou post, you said "least-squares gradient reconstruction with full extended neighborhood".

Is this same to "least squares method over extended cell neighborhood" in Ver.6?

Best regards,
Tsubasa
Yvan Fournier
Posts: 4070
Joined: Mon Feb 20, 2012 3:25 pm

Re: Divergence for simple geometry room

Post by Yvan Fournier »

Hello,

Yes, it is the same.

Best regards,

Yvan
Tsubasa
Posts: 175
Joined: Fri Nov 20, 2020 4:09 am

Re: Divergence for simple geometry room

Post by Tsubasa »

Hello Yvan,

As you said, a simulation can be done by "least squares method over extended cell neighborhood" in Ver.6,
but the pressure difference flow simulation had a divergence problem.

In my case, pressure difference is just 0.6Pa. This is very small, but the result became divergent.

Best regards,
Tsubasa
Tsubasa
Posts: 175
Joined: Fri Nov 20, 2020 4:09 am

Re: Divergence for simple geometry room

Post by Tsubasa »

Hello Yvan,

Do you think Ver.7 is more stable for computation than Ver.6?
(Idealy, I want to conduct a pressure driven flow by steady simulation (not URANS).)
If you think so, I want to try it with Ver.7.

If it is possible, every problem can be solved, which is posted in another post.

Best regards,
Tsubasa
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