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May 21, 2013, 11:00 
Nondimensionzalized icoFoam

#1 
New Member
OFghost
Join Date: Feb 2013
Location: Canada
Posts: 8
Rep Power: 5 
Hi All,
I am trying to perform nondimensionalization of icoFoam. Please have a look of attached file which is modification which I am having now. I have turnedoff 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) Nondimensionaliztion 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 

May 21, 2013, 16:58 

#2  
Senior Member
Cyprien
Join Date: Feb 2010
Location: Stanford University
Posts: 251
Rep Power: 10 
Quote:
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 turningoff 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 

May 22, 2013, 05:12 

#3  
Senior Member

Quote:
I would really like to appreciate you for working with nondimensional 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 

May 22, 2013, 13:25 

#4  
New Member
OFghost
Join Date: Feb 2013
Location: Canada
Posts: 8
Rep Power: 5 
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 nondimensionalize geometry?? Thanks Umar Quote:


May 23, 2013, 00:57 

#5  
Senior Member

Quote:
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. 

June 5, 2013, 12:12 

#6 
Member
Mehrez
Join Date: Nov 2012
Location: Bordeaux, France
Posts: 80
Rep Power: 6 
Hi Umar
Did you resolve your problem ? In order to nondimensionalize 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). Mehrez 

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