Problem with the cylindrical coordinates

langloi

Hi,
I need your help, so any help is welcome.
I want resolve this equation in O.FOAM:
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Laplacian(V)+ (1/r)*V=Source
V is volScalarField
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it's written in cylindrical coordinate(r,theta,z).
In my case I consider the X like axis of rotation and Y like the direction (r) with (X,Y,Z) is cartesian coordinates.
I write my equation in O.Foam like that:
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Laplacian(V)+ (1/y)*V=Source
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with y=mesh.C().component(vector::Y);
But the result of this way of writing gives the different result with the Literature.
thank you for your help