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Convergence in OpenFoam

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Old   September 8, 2011, 06:30
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Jignesh
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hi
i m using openfoam200 & i solved tutorial of LCD so i have one doubt is it possible in openfoam to give the residue limits & after achieving that limit the program will stop? if yes then plz tel me how is it possible?

i m still waiting for reply
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Old   September 8, 2011, 14:03
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David Gaden
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Residual limits? I assume you mean the convergence criteria. These are located in the fvSolution file.
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Old   September 8, 2011, 17:58
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Alberto Passalacqua
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The "search" function is always your friend ;-)
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GeekoCFD - A free distribution based on openSUSE 64 bit with CFD tools, including OpenFOAM. Available as in both physical and virtual formats (current status: http://albertopassalacqua.com/?p=1541)
OpenQBMM - An open-source implementation of quadrature-based moment methods.

To obtain more accurate answers, please specify the version of OpenFOAM you are using.
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Old   September 9, 2011, 06:56
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yes sir i know it is placed in fvsol dict. but i dont know that how to stop the programe when conversion limit cross.

like in fluent when conversion criteria satisfy then stop the program automatically but in openfoam when it reach the exit time then it stop

so i eager to know sir how can i stop my program automatically when it reaches over the conversion limits

plz reply me

yours faithfully
jignesh
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Old   September 9, 2011, 16:20
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Alberto Passalacqua
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If you specify a convergence criterion, the solver will stop automatically.

Best,
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GeekoCFD - A free distribution based on openSUSE 64 bit with CFD tools, including OpenFOAM. Available as in both physical and virtual formats (current status: http://albertopassalacqua.com/?p=1541)
OpenQBMM - An open-source implementation of quadrature-based moment methods.

To obtain more accurate answers, please specify the version of OpenFOAM you are using.
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Old   September 9, 2011, 17:07
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Quote:
Originally Posted by alberto View Post
If you specify a convergence criterion, the solver will stop automatically.

Best,

ya i know but suppose in cavity tutorial tolerance is given same as conversion criteria.
so if i want to stop my program when it will go beyond my conversion criteria then what should i write in fvsol dict.

plz tel me
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Old   March 6, 2013, 14:05
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I am trying to solve equation

fvScalarMatrix CEqn
(
fvm::ddt(C)
+ fvm::div(phi, C)

);
CeqnResidual = CEqn.solve().initialResidual();

In case where phi is zero (i.e. no flow), my initial residuals are always high (~ 0.3). When I am forcing the solver to exit without satisfying the convergence criterion (by setting a maximum for the iterations), I see that phi is zero everywhere and C is constant, as I expect. But, I don't know why CeqnResidual is high!
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Old   June 4, 2019, 04:14
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Hi all,

Thanks for all those questions and answers on convergence, they helped me a lot!

I'm aware that this thread is rather old, but my question is similar to other questions asked here, so I'll post here anyway.

At the moment I'm using interFoam for marine hydrodynamics, calm water resistance computations on ship hulls. For this type of simulations it's often necessary to apply velocity ramping at the start, which makes the simulation inherently transient. However, after this velocity ramp at start-up, the simulation should normally converge to a steady solution, which is really all I'm interested in.

Is there a way in OpenFOAM to stop a transient simulation when a steady solution is reached?

Many thanks!
Sita

Last edited by sita; June 4, 2019 at 10:37.
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Old   April 11, 2023, 05:53
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Dear Alberto
My residuals are like this(see attached figure), and they do not goes down to 10e-4(or 10e-5), but my value of interest which is drag coefficient (Cd) is constant. Can I rely on my obtained results? or what should I do? do you have any suggestion?


Thanks,
Farzad

Quote:
Originally Posted by alberto View Post
Machine zero (or machine epsilon http://en.wikipedia.org/wiki/Machine_epsilon ) depends on the machine. As reference, 1.0 x 10^-12 is what I use as reference. Someone uses smaller numbers.

Best,
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