axisymmetric cylinder and piston for OpenFOAM

blockMeshDict

//following this: https://openfoamwiki.net/index.php/Main_ContribExamples/AxiSymmetric

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  5                                     |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;

    root            "";
    case            "";
    instance        "";
    local           "";

    class       dictionary;
    object      blockMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

convertToMeters 0.001;

wa 5.0; // wedge angle must be 5 degrees
cr 10.0; // cylinder radius
pr 8.0; //piston radius
cl 50.0; // length of cylinder
px 20.0; // position of piston
pl 10.0; // length of piston
px2 #calc "$px+$pl"; // end of the piston
ms 50; //meshsize



vertices
(
    (0                      0                         0)    //00
    (#calc "$pr*cos($wa/2)" #calc "$pr*sin($wa/2)"    0)    //01
    (#calc "$pr*cos($wa/2)" #calc "-$pr*sin($wa/2)"   0)    //02
    (#calc "$pr*cos($wa/2)" #calc "-$pr*sin($wa/2)"   $px)  //03
    (#calc "$pr*cos($wa/2)" #calc "$pr*sin($wa/2)"    $px)  //04
    (0                      0                         $px)  //05
    (#calc "$cr*cos($wa/2)" #calc "$cr*sin($wa/2)"    $px)  //06
    (#calc "$cr*cos($wa/2)" #calc "$cr*sin($wa/2)"    0)    //07
    (#calc "$cr*cos($wa/2)" #calc "-$cr*sin($wa/2)"   0)    //08
    (#calc "$cr*cos($wa/2)" #calc "-$cr*sin($wa/2)"   $px)  //09
    (#calc "$cr*cos($wa/2)" #calc "-$cr*sin($wa/2)"   $px2) //10
    (#calc "$cr*cos($wa/2)" #calc "$cr*sin($wa/2)"    $px2) //11
    (#calc "$pr*cos($wa/2)" #calc "$pr*sin($wa/2)"    $px2) //12
    (#calc "$pr*cos($wa/2)" #calc "-$pr*sin($wa/2)"   $px2) //13
    (#calc "$pr*cos($wa/2)" #calc "-$pr*sin($wa/2)"   $cl)  //14
    (#calc "$pr*cos($wa/2)" #calc "$pr*sin($wa/2)"    $cl)  //15
    (#calc "$cr*cos($wa/2)" #calc "$cr*sin($wa/2)"    $cl)  //16
    (#calc "$cr*cos($wa/2)" #calc "-$cr*sin($wa/2)"   $cl)  //17
    (0                      0                         $cl)  //18
    (0                      0                         $px2) //19
);

blocks
(
    hex (0  1  2  0  5  4  3  5)         ($ms 1 $ms) simpleGrading (1 1 1)
    hex (1  7  8  2  1  4  6  9  3  4)   ($ms 1 $ms) simpleGrading (1 1 1)
    hex (4  6  9  3  4  12 11 10 13 12)  ($ms 1 $ms) simpleGrading (1 1 1)
    hex (12 11 10 13 12 15 16 17 14 15)  ($ms 1 $ms) simpleGrading (1 1 1)
    hex (19 12 13 19 18 15 14 18)        ($ms 1 $ms) simpleGrading (1 1 1)
);

edges
(
);

boundary
(
    inlet
    {
        type patch;
        faces
        (
            (0 1 2 0)
            (1 7 8 2)
        );
    }
    outlet
    {
        type patch;
        faces
        (
            (18 15 14 18)
            (15 16 17 14)
        );
    }
    walls
    {
        type wall;
        faces
        (
            (7  8  9  6)
            (6  9  10 11)
            (11 10 17 16)
        );
    }
    wedges
    {
        type wedge;
        faces
        (
            (0  1  4  5)
            (1  7  6  4)
            (4  6  11 12)
            (12 11 16 15)
            (19 12 15 18)
            (0  5  3  2)
            (2  3  9  8)
            (3  13 10 9)
            (13 14 17 10)
            (19 18 14 13)
        );
    }
    axis
     { 
           type empty;
           faces  
           (
               (0  5  5  0)
               (19 18 18 19)
           );
    }
);

mergePatchPairs
(
);

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

relevant discussions here and here.