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Perform calculations using neighbouring cell data

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Old   July 26, 2021, 07:14
Default Perform calculations using neighbouring cell data
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Elliott Sutton
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Hi everyone,

I'm quite new to programming with OpenFOAM and need some help.

I am trying to create a new scalar field that calculates the total difference in viscosity between a given cell and all of its neighbouring cells. What is the syntax I need to get the value of a variable in a given cell and the value in all cells directly adjacent?

I'm hoping to get this to work for an AMR method and to work in parallel.

Thanks,

Elliott
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Old   July 26, 2021, 12:43
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Michael Alletto
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How to get the neighbour of one cell?

Just a few seconds googling helps a lot
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Old   August 3, 2021, 06:01
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Elliott Sutton
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Quote:
Originally Posted by mAlletto View Post
How to get the neighbour of one cell?

Just a few seconds googling helps a lot
Thank you for this.

I've performed the calculation as shown below, but receive the error that " 'celli' was not declared in this scope". I'm not sure how to properly declare 'celli' as any cell in the mesh. Any help would be appreciated.

Declaration of the variable in the .C file, initialised based on a viscosity field:
Code:
    etaGrad_
    (
        IOobject
        (
            "etaGrad" + name,
            U.time().timeName(),
            U.mesh(),
            IOobject::NO_READ,
            IOobject::AUTO_WRITE
        ),
        eta_
    ),
The actual calculation in .C:
Code:
   
   const objectRegistry& db();
   const volVectorField& U = db().lookupObject<volVectorField>("U");
   const fvMesh& mesh = U.mesh();
   const labelList& neighbour = mesh.cellCells[celli]();
   
   forAll(neighbour,celli)
   {
      etaGrad_[celli] += mag(eta_[celli] - eta_[neighbour[celli]]);
   }
Declaration in the .H file:
Code:
        //- Viscosity gradient field
        volScalarField etaGrad_;
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