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Convergence in higher velocity

Posted Oct 19, 2023, 2:45 a.m. EDT Version 6.1 1 Reply

Senapati Sri Krishnamurti
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Hi All,

i have a CFD Model for a flow cell with laminar flow. Im supposed to implement this model for inlet velocity of 0.9, 4.71, 9.43, 23.57 and 47.157 cm/s. But, if i input the last two inlet velocities (23.57 and 47.157 cm/s), it doesnt converge. I defined the inlet with inlet velocity configuration and the outlet with pressure boundary condition (static pressure). Can anyone help me with this problem? How should i optimize the model so it converges? I attached the model here...

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1 Reply Last Post Oct 24, 2023, 1:54 p.m. EDT
Eric Favre
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Posted: 6 months ago Oct 24, 2023, 1:54 p.m. EDT
Updated: 6 months ago Oct 24, 2023, 1:54 p.m. EDT

Hi Senapati,
I suggest you to multiply your viscosity in your material by a constant "c". Define c=10 as a parameter and solve to check it converges with your highest velocity. Then instead of ramping the velocity, ramp down the coefficient c from 10 to 1 (just put those 2 values). That should help the convergence so that you get your result at the velocity you want. Afterwards, just check that your mesh is fine enough to solve for the boundary layer : compute size = d/sqrt(Re), where d is typically your diameter. Check with your mesh size, you should get a few mesh elements throughout your boundary layer.
Good luck!
Eric Favre
Renaissance Fusion

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Eric Favre
Renaissance Fusion
Hi Senapati, I suggest you to multiply your viscosity in your material by a constant "c". Define c=10 as a parameter and solve to check it converges with your highest velocity. Then instead of ramping the velocity, ramp down the coefficient c from 10 to 1 (just put those 2 values). That should help the convergence so that you get your result at the velocity you want. Afterwards, just check that your mesh is fine enough to solve for the boundary layer : compute size = d/sqrt(Re), where d is typically your diameter. Check with your mesh size, you should get a few mesh elements throughout your boundary layer. Good luck! Eric Favre Renaissance Fusion

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