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November 7, 2013, 06:48 |
Turbulrnt flow past cylinder
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#1 |
Senior Member
Join Date: Sep 2013
Location: Bangalore India
Posts: 134
Rep Power: 12 |
Hi Foamers,
I set up the case of transient flow past circular cylinder with following conditions Re = 3.6*10^6 Velocity = 3.6 m/s turbulent intensity = 0.5% I am getting an error as attached in a snapshot and also i have attached the 0 directory. ControlDict is as follows. [/*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: 2.2.1 | | \\ / A nd | Web: www.OpenFOAM.org | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class dictionary; location "system"; object controlDict; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // libs ( "libOpenFOAM.so" "libincompressibleTurbulenceModel.so" "libincompressibleRASModels.so" ); application pimpleFoam; startFrom startTime; startTime 0; stopAt endTime; endTime 1000; deltaT 0.001; writeControl adjustableRunTime; writeInterval 100; purgeWrite 0; writeFormat ascii; writePrecision 6; writeCompression uncompressed; timeFormat general; timePrecision 6; runTimeModifiable true; adjustTimeStep yes; maxCo 1; functions { probes { // Where to load it from functionObjectLibs ( "libsampling.so" ); type probes; // Name of the directory for probe data name probes; // Write at same frequency as fields outputControl outputTime; outputInterval 1; // Fields to be probed fields ( p U ); probeLocations ( ( -6 0 0 ) // at inlet ( 30 0 0 ) // at outlet ( 18 0 0 ) // at central block ); } } // ************************************************** *********************** //] |
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November 8, 2013, 03:28 |
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#2 |
New Member
Join Date: Oct 2013
Posts: 15
Rep Power: 12 |
Its a problem of your courant number as you see in your terminal picture.
your maximum courant number is set to 1 but you get some of 10^28. It would be helpful to take a shorter write interval and have a look at some pressure peaks before the breakdown. what's the difference between your fixed walls and walls? greeting pingat |
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November 8, 2013, 03:34 |
Specifying Boundary Conditions in pimpleFOAM
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#3 |
Senior Member
Join Date: Sep 2013
Location: Bangalore India
Posts: 134
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Hi
Here are the boundaries specified and the case geometry and mesh are shown in this snap shot attached with this mail. |
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November 8, 2013, 03:45 |
Constant and system directories of the case
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#4 |
Senior Member
Join Date: Sep 2013
Location: Bangalore India
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Hi
Kindly find the attached system and constant directories for reference. |
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November 8, 2013, 03:38 |
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#5 | |
Senior Member
Join Date: Sep 2013
Location: Bangalore India
Posts: 134
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Quote:
I just run the case with write interval of 0.5 but the problem remains the same as before.. No change at all... Can you tell how to resolve this problem |
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November 8, 2013, 03:56 |
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#6 | |
New Member
Join Date: Oct 2013
Posts: 15
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Quote:
there you get a time step of 10^-60 and a high courant number, so maybe there is a problem in your meshing? maybe you could post a pressure and velocity picture at that time. |
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November 8, 2013, 06:47 |
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#7 |
Senior Member
Join Date: Sep 2013
Location: Bangalore India
Posts: 134
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Hi ,
I am running the case but one thing i ma observing that deltaT=0.001 in control dict but its displaying deltaT of the order of 10^-7 and simulation is very slow... Why is this so ? As per my knowledge whichever deltaT we have specified in controlDict that value has to be come on terminal box. Can anyone clarify this please . |
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November 9, 2013, 04:57 |
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#8 |
New Member
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if there is no convergence at the given timestep, the solver trys to take a smaller step.
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November 10, 2013, 23:04 |
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#9 |
Senior Member
Join Date: Sep 2013
Location: Bangalore India
Posts: 134
Rep Power: 12 |
Hi pingat ,
What might be the reason for non convergence ???????? |
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November 28, 2013, 21:57 |
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#10 |
Senior Member
Join Date: Jan 2013
Posts: 134
Rep Power: 13 |
I also get this error from time to time, then I changed the mesh a little, the problem disappeared. I've no idea why.
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