[saeed jamshidi]

Hello,

I'm wondering why it take longer time for execution of snappyHexMesh at the moment that I'm considering empty for front and back faces of my solution in comparison to the condition that front and back are patch or symmetry type?!
Shall I consider

defaultPatch
{
    name frontAndBack;
    type empty;
}

istead of below type?

This is my blockMeshDict:

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  v2112                                |
|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      blockMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

scale 1;

vertices
(
    (-0.4 -0.4 0.01) //0
    (1 -0.4 0.01) //1
    (1 0.4 0.01)  //2
    (-0.4 0.4 0.01)  //3
	
    (-0.4 -0.4 -0.01)  //4
    (1 -0.4 -0.01)  //5
    (1 0.4 -0.01)  //6
    (-0.4 0.4 -0.01)  //7
);

blocks
(
    hex (4 5 6 7 0 1 2 3) (140 80 1) simpleGrading (1 1 1)
);

edges
(
);

boundary
(
    
    inlet
    {
        type patch;
        faces
        (
            (0 4 7 3)
        );
    }
    outlet
    {
        type patch;
        faces
        (
            (1 5 6 2)
        );
    }
	topAndBottom
    {
        type patch;
        faces
        (
            (3 2 6 7)
			(0 1 5 4)
        );
    }

	frontAndBack
    {
        type empty;
        faces
        (
			(0 1 2 3)
			(4 5 6 7)	
        );
    }

);

mergePatchPairs
(
);

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

I would appreciate it if you help me in this matter.