CFD Online Discussion Forums - [Other] how run a DNS for ZPG turbulent boundary layer on a plate with OpenFOAM?

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how run a DNS for ZPG turbulent boundary layer on a plate with OpenFOAM?

Hello
i need to run a direct numerical simulation for my research on Zero Pressure Gradient (ZPG) Turbulent Boundary Layer (TBL) on a plate.
i find that perhaps i can do this with dnsFoam in OpenFOAM.
but i am beginner in OpenFOAM, i run dnsfoam from tutorial but when i want change the mesh size from 16*16*16 to for example 32*32*32 and run the solver by type dnsFoam in terminal below error appeared.

Code:

/*---------------------------------------------------------------------------*\

| =========                 |                                                 |

| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |

|  \\    /   O peration     | Version:  2.1.0                                 |

|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |

|    \\/     M anipulation  |                                                 |

\*---------------------------------------------------------------------------*/

Build  : 2.1.0-0bc225064152

Exec   : dnsFoam

Date   : Mar 17 2012

Time   : 18:52:22

Host   : "ubuntu"

PID    : 5381

Case   : /home/ashkan/OpenFOAM/ashkan-2.1.0/run/DNS/dnsFoam/boxTurb16

nProcs : 1

sigFpe : Enabling floating point exception trapping (FOAM_SIGFPE).

fileModificationChecking : Monitoring run-time modified files using timeStampMaster

allowSystemOperations : Disallowing user-supplied system call operations



// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

Create time



Create mesh, no clear-out for time = 0



Reading transportProperties



Reading field p



Reading field U







--> FOAM FATAL IO ERROR: 

size 4096 is not equal to the given value of 32768



file: /home/ashkan/OpenFOAM/ashkan-2.1.0/run/DNS/dnsFoam/boxTurb16/0/U from line 18 to line 4146.



    From function Field<Type>::Field(const word& keyword, const dictionary&, const label)

    in file /home/opencfd/OpenFOAM/OpenFOAM-2.1.0/src/OpenFOAM/lnInclude/Field.C at line 236.



FOAM exiting

please help me and if possible tell me what can i do?

Quote:

--> FOAM FATAL IO ERROR:
size 4096 is not equal to the given value of 32768

file: /home/ashkan/OpenFOAM/ashkan-2.1.0/run/DNS/dnsFoam/boxTurb16/0/U from line 18 to line 4146.

If you look at this file (where you see the boundary and initial conditions for U), you will see 4096 (16x16x16) initial values for U. Since the mesh is changed, the fields will have to be adjusted to this modification. You need to use the utility mapFields (you should find information in this forum but also in the manual if I am not mistaken, in the cavity example).

And read the manual again. :-)

anon_a's diagnosis was right, but there is a really easier way to solve it. This case is being initialized with boxTurb, not by mapFields or else.

Go to root/0 directory, open U file and change the internalField nonuniform bla bla to internalField uniform (0 0 0); then run the boxTurb utility and you're good to go

Boundary Layer DNS using dnsFoam?

Did you modify the code dnsFoam for zpg boundary layer flow? dnsFoam is for isotropic turbulence.