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Non-dimensionzalized icoFoam

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Old   May 21, 2013, 11:00
Default Non-dimensionzalized icoFoam
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Hi All,
I am trying to perform non-dimensionalization of icoFoam. Please have a look of attached file which is modification which I am having now.
I have turned-off dimensional consistency check as solver always complains about it. Calculations are performed but in my view they are not physically meaningful.
1 ) I am wondering whether solver is not itself not correct, having some mistake??
2) Non-dimensionaliztion of geometry is also needed, as far as I know, then how it could be implemented??
Any help regarding this, would be highly appreciated.
Many Thanks
Umar
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File Type: c myIcoFoamB.C (3.1 KB, 11 views)
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Old   May 21, 2013, 16:58
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Cyp
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Quote:
Originally Posted by umar82088 View Post
Hi All,
I am trying to perform non-dimensionalization of icoFoam. Please have a look of attached file which is modification which I am having now.
I have turned-off dimensional consistency check as solver always complains about it. Calculations are performed but in my view they are not physically meaningful.
1 ) I am wondering whether solver is not itself not correct, having some mistake??
2) Non-dimensionaliztion of geometry is also needed, as far as I know, then how it could be implemented??
Any help regarding this, would be highly appreciated.
Many Thanks
Umar

Hello Umar,

I had a glance at your enclosed file. First of all, you can not get rid of the temporal term. Indeed, you attempt to modify a PISO loop and this latter is created to solve an unsteady problem ! If you really need a steady solver, have a look at simpleFoam.

Second point, instead of turning-off the dimensions check, I will have defined new dimensionedScalar (for example unit1) that is equal to 1 and have suitable dimensions and write : unit1*fvm::div(phi,U).

Regards,
Cyp
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Old   May 22, 2013, 05:12
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Quote:
Originally Posted by umar82088 View Post
Hi All,
I am trying to perform non-dimensionalization of icoFoam. Please have a look of attached file which is modification which I am having now.
I have turned-off dimensional consistency check as solver always complains about it. Calculations are performed but in my view they are not physically meaningful.
1 ) I am wondering whether solver is not itself not correct, having some mistake??
2) Non-dimensionaliztion of geometry is also needed, as far as I know, then how it could be implemented??
Any help regarding this, would be highly appreciated.
Many Thanks
Umar
Hi Umar,

I would really like to appreciate you for working with non-dimensional form of equation.
I totally agree with Cyp, it appears that you are not using the transient term in your equation. So, try with simpleFoam.

I would rather write the equation like this...

(
fvm::div(phi, U)
- fvm::laplacian(1/Re, U)
);

solve (UEqn == -fvc::grad(p));

Anyways, you need to be careful about the extra dimensions, see the weblink for better explanation:

Dimensionless variables
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Old   May 22, 2013, 13:25
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Hi Tushar,
First of all thanks for replying on the post. I made a mistake that I commented over the temporal term, which I didn't intend to do. My Problem needs to be solved in transient way. I have modified the code as you mentioned, now problem is arising with the discritization part. As we have to modify that part accordingly. Any suggestion to trick with that issue. And secondly how to non-dimensionalize geometry??

Thanks
Umar
Quote:
Originally Posted by Tushar@cfd View Post
Hi Umar,

I would really like to appreciate you for working with non-dimensional form of equation.
I totally agree with Cyp, it appears that you are not using the transient term in your equation. So, try with simpleFoam.

I would rather write the equation like this...

(
fvm::div(phi, U)
- fvm::laplacian(1/Re, U)
);

solve (UEqn == -fvc::grad(p));

Anyways, you need to be careful about the extra dimensions, see the weblink for better explanation:

Dimensionless variables
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Old   May 23, 2013, 00:57
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Quote:
Originally Posted by umar82088 View Post
Hi Tushar,
First of all thanks for replying on the post. I made a mistake that I commented over the temporal term, which I didn't intend to do. My Problem needs to be solved in transient way. I have modified the code as you mentioned, now problem is arising with the discritization part. As we have to modify that part accordingly. Any suggestion to trick with that issue. And secondly how to non-dimensionalize geometry??

Thanks
Umar
Hi,

I think you need to follow either of the procedure described on the forum:

(1) Dimensionless variables
(2) Dimensionless equations, variables, mesh etc

I haven't tried any of these but it seems both the procedure will do the job.
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Old   June 5, 2013, 12:12
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Hi Umar

Did you resolve your problem ?

In order to non-dimensionalize your geometry you need to divide all the dimensions by a characteristic length that you will choose and this characteristic length will appear in your Re number.
Then, you can enter this dimensions in your OpenFoam file (MeshDict).


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