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October 3, 2007, 12:13 
Hi all,
I have created a thre

#1 
New Member
Gabriele Ruggieri
Join Date: Mar 2009
Location: Milan, Italy
Posts: 1
Rep Power: 0 
Hi all,
I have created a threedimensional fuel rotating pump leaving from the MRFSimpleFoam tutorial in OpenFoam1.4.1. There are two regions, one cylindrical inner that rotates at 720 rad/s and one external fixed. They are connected with three interfaces ggi: one on top, one lateral and one on bottom. There is also inlet and outlet. The MRFZones are defined like in the tutorial with rotor and stator. After one timeStep the residual value increse and I don't know why. I have tried the mixer2d icoDyMFoam tutorial and a lot of other cases with this method and they work very well. Here there are the log file, p, U and MRFZones /**\  =========    \ / F ield  OpenFOAM: The Open Source CFD Toolbox   \ / O peration  Version: 1.4.1   \ / A nd  Web: http://www.openfoam.org   \/ M anipulation   \**/ Exec : MRFSimpleFoam . pump Date : Oct 03 2007 Time : 15:22:47 Host : sarge PID : 27336 Root : /gamma/grugg/OpenFOAM/OpenFOAM1.4.1/tutorials/MRFSimpleFoam Case : pump Nprocs : 1 Create time Create mesh for time = 0 Reading field p Reading field U Reading/calculating face flux field phi Selecting incompressible transport model Newtonian Selecting turbulence model laminar Starting time loop Time = 1 smoothSolver: Solving for Ux, Initial residual = 0, Final residual = 0, No Iterations 1 smoothSolver: Solving for Uy, Initial residual = 0, Final residual = 0, No Iterations 1 smoothSolver: Solving for Uz, Initial residual = 0, Final residual = 0, No Iterations 1 PCG: Solving for p, Initial residual = 1, Final residual = 9.85725e07, No Iterations 767 PCG: Solving for p, Initial residual = 0.00230797, Final residual = 9.98469e07, No Iterations 148 PCG: Solving for p, Initial residual = 0.000382438, Final residual = 9.98736e07, No Iterations 297 PCG: Solving for p, Initial residual = 8.68112e05, Final residual = 9.9683e07, No Iterations 15 PCG: Solving for p, Initial residual = 2.74264e05, Final residual = 9.87837e07, No Iterations 8 time step continuity errors : sum local = 4.03381, global = 0.0905555, cumulative = 0.0905555 ExecutionTime = 91.13 s ClockTime = 92 s Time = 2 smoothSolver: Solving for Ux, Initial residual = 0, Final residual = 0, No Iterations 1 smoothSolver: Solving for Uy, Initial residual = 0, Final residual = 0, No Iterations 1 smoothSolver: Solving for Uz, Initial residual = 0, Final residual = 0, No Iterations 1 PCG: Solving for p, Initial residual = 0.997299, Final residual = 0.393761, No Iterations 7000 **\  =========    \ / F ield  OpenFOAM: The Open Source CFD Toolbox   \ / O peration  Version: 1.4.1   \ / A nd  Web: http://www.openfoam.org   \/ M anipulation   \**/ FoamFile { version 2.0; format ascii; root ""; case ""; instance ""; local ""; class volScalarField; object p; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // dimensions [0 2 2 0 0 0 0]; internalField uniform 106000; boundaryField { inlet { type totalPressure; p0 uniform 106000; U U; phi phi; rho none; psi none; gamma 1.0; } outlet { type outletInlet; outletValue uniform 106066; } rotor { type zeroGradient; } stator { type zeroGradient; } outsideSliderTop { type ggi; } outsideSliderBottom { type ggi; } outsideSliderLateral { type ggi; } insideSliderTop { type ggi; } insideSliderBottom { type ggi; } insideSliderLateral { type ggi; } } // ************************************************** *********************** // /**\  =========    \ / F ield  OpenFOAM: The Open Source CFD Toolbox   \ / O peration  Version: 1.4.1   \ / A nd  Web: http://www.openfoam.org   \/ M anipulation   \**/ FoamFile { version 2.0; format ascii; root "/gamma/grugg/OpenFOAM/OpenFOAM1.4.1/tutorials/MRFSimpleFoam"; case "pompaGRUGG_2"; instance "0"; local ""; class volVectorField; object U; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // dimensions [0 1 1 0 0 0 0]; internalField uniform (0 0 0); boundaryField { rotor { type fixedValue; value uniform (0 0 0); } insideSliderTop { type ggi; value uniform (0 0 0); } insideSliderLateral { type ggi; value uniform (0 0 0); } insideSliderBottom { type ggi; value uniform (0 0 0); } stator { type fixedValue; value uniform (0 0 0); } outsideSliderTop { type ggi; value uniform (0 0 0); } outsideSliderLateral { type ggi; value uniform (0 0 0); } outsideSliderBottom { type ggi; value uniform (0 0 0); } inlet { type pressureInletVelocity; value uniform (0 0 0); } outlet { type inletOutlet; inletValue uniform (0 0 0); } } // ************************************************** *********************** // /**\  =========    \ / F ield  OpenFOAM: The Open Source CFD Toolbox   \ / O peration  Version: 1.4.1   \ / A nd  Web: http://www.openfoam.org   \/ M anipulation   \**/ FoamFile { version 2.0; format ascii; root ""; case ""; instance ""; local ""; class dictionary; object MRFZones; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // 1 ( rotor { patches (rotor); origin origin [0 1 0 0 0 0 0] (0 0 0); axis axis [0 0 0 0 0 0 0] (0 0 1); omega omega [0 0 1 0 0 0 0] 720; } ) // ************************************************** *********************** // First region, omega = 720 rad/s rotor (blades) insideSliderTop insideSliderLateral insideSliderBottom Second region, fixed stator (external wall) outsideSliderTop outsideSliderLateral outsideSliderBottom inlet outlet Please can anyone help me ? I'm sorry, my english is not good. Thanks Gabriele 

March 29, 2008, 11:07 
hi:
have you ever resolve yo

#2 
Senior Member

hi:
have you ever resolve your problem?try to modify the initial condition? 

June 26, 2008, 10:02 
MRFSimpleFoam computes relativ

#3 
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David Hora
Join Date: Mar 2009
Location: Zürich, Switzerland
Posts: 63
Rep Power: 9 
MRFSimpleFoam computes relative fluxes for the cell faces of the rotating frame. The affected faces are listed in faceZones. I assume that the flux is treated as absolute for the control surfaces of the ggi interface. Does anybody know it more precisely and how would it be possible to make the fluxes relative at the interface?
Regards david 

June 19, 2010, 12:27 
MRFSimpleFoam 2nd order convergence

#4 
Member
Aldo Iannetti
Join Date: Feb 2010
Posts: 48
Rep Power: 8 
Hi
I'm trying to simulate a 3D cooling fan using OF 1.6 and MRFSimpleFoam, I'm interested in a second order upwind solution. My grid is 3D, unstructured, tetraedral and imported from GAMBIT. The rotational velocity has been given step by step growing from 50 rad/s to 272 rad/s. Residuals go down till 4000 iterations after that they start to increase and diverge. Here attached my fvSchemes and the log file. Can you please give me advices about settings (under relaxation, discretization schemes etc..) Thanks 

July 19, 2010, 23:16 
Convergence issues

#5 
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Join Date: Jul 2010
Posts: 17
Rep Power: 8 
I am running MRFSimpleFoam on a wind turbine blade using the SpallartAllmaras turbulence model. I am using inletOutlet BCs on p, U, rho and fixedValues of nut and nuTilda on the outer boundary but after 300 iterations the residuals begin to diverge and eventually blow up. Has anyone seen this before or have any idea why this is happening?


March 28, 2014, 04:43 
Turbulence convergence problems

#6 
Member

I have had all described problems in my 2blade rotor case.
It seems that the solution should be such as written below: 1. upwind schemes for K and Omega 2. low 1e6 meanings for both variables at inlets and openings, at walls i've left it for a small value corellate to velocity of the wall. I used wallFunctions.
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March 28, 2014, 05:21 

#7 
Senior Member

Hi Ilya,
First of all your question is not clear, no body have time to read all the post from the beginning, so be specific about your problem, as well the thread you chosen is nearly 4 years old, the people involved in that discussion may have forgotten the solution to the problem, try to find the latest thread or else start new one. there are few questions > are you using wall function? or resolving boundary layer? if you are intending to use wall function, the value for k and omega should be estimated in standard way. In the case of Low Re (resolving boundary layer), you should give k and Omega small value 1e8. For turbulent quantities, first order upwind scheme is recommended. if this answer didt help you, please post you problem clearly. Thanks, Sivakumar 

March 28, 2014, 05:56 

#8  
Member

Quote:
2. Yes, i'm using wall functions and all variables are calculated but it needs initial values anyway. 3. Despite to my suggestions problem stands still. OpenFOAM does not crash due to high k and omega but pressure field is not realistic.
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