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Residuals Behaviour

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Old   April 28, 2020, 16:41
Post Residuals Behaviour
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Hello all,

I am not familiar with CFD. I have applied some basic settings, boundary conditions, and started calculating.

The curves look like converging.

The question is, the starting point of the curve is not from "Zero".

Is it common or did I made anything wrong?

Any type of suggestion is highly appreciated.

Thank you
Raj
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Old   April 29, 2020, 11:09
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Why do you expect residuals to start from 0? Ideally, it should be 0 when the case is converged. Practically, it is never 0 because the system is numerical and discrete.
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Old   April 30, 2020, 07:47
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Can you give me some more information, if possible?

And is the my solution according to your reply?

Thank you
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Old   April 30, 2020, 08:20
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The residuals look alright, as expected. However, the case setup may or may not be complete. First of all, flow most likely would be turbulence and you will have to enable a turbulence model. Secondly, you should always enable gravity for a multiphase case with appropriate values for operating density and reference pressure location. And it will take a lot of iterations, usually, 1000s for convergence.
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Old   April 30, 2020, 11:32
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No, it is the laminar model. Yeah, I have given 1000 iterations. I just posted it while it was simulating. I am just confused about that, can I consider this convergence is correct or not?
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Old   April 30, 2020, 11:42
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Residuals are not good for checking convergence. You should create a few monitors, such as, velocity at outlet, and/or pressure or volume fraction at outlet or in the domain. Once these monitors stop oscillating, then the solution should be considered converged.
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