[prka0002]

Can setExprFields be used to enforce symmetric field about a plane? What is required is mentioned in the dict File below.

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  v2006                                 |
|   \\  /    A nd           | Website:  www.openfoam.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      setExprFieldsDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

expressions
(
    U
    {
        field       U;
        dimensions  [0 1 -1 0 0 0 0];

//        constants
//        {
//        }

        variables
        (
         //
        );

        condition
        #{
           (pos().y() < 0)
        #};

        expression
        #{
            vector
            (
             //To Do: mirror of velocity fields at pos().y()>0 to enforce symmetry through whole domain. Mesh is a 2D rectangular domain which has reflectional symmetry about y=0. (x-horizontal axis, y-vertical) 
             // simulation of half domain and implementation of reflect filter in paraview works however, what is required is a code for enforcing symmetry at every time step by reflecting field values 
             //of top half of domain to bottom half. setExprFields here is to figure this problem out (if that works) and take it as a reference which can be added to the code itself later. 
            )
        #};
    }
);

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

Any solution ideas to this problem works, doesn't have to be setExprFields only. This is just a reference. Thank you in advance!