[lucamazzotta]

Hi, I'm getting this error while trying to create a simple quadrilateral mesh:

/*---------------------------------------------------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     | Website:  https://openfoam.org
    \\  /    A nd           | Version:  7
     \\/     M anipulation  |
\*---------------------------------------------------------------------------*/
Build  : 7
Exec   : blockMesh
Date   : Nov 25 2022
Time   : 16:23:57
Host   : "hurricane"
PID    : 565873
I/O    : uncollated
Case   : /home/lm519/Desktop/OpenFOAM/backwardsStepTest
nProcs : 1
sigFpe : Enabling floating point exception trapping (FOAM_SIGFPE).
fileModificationChecking : Monitoring run-time modified files using timeStampMaster (fileModificationSkew 10)
allowSystemOperations : Allowing user-supplied system call operations

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
Create time

Creating block mesh from
    "/home/lm519/Desktop/OpenFOAM/backwardsStepTest/system/blockMeshDict"
Creating block edges
No non-planar block faces defined
Creating topology blocks
--> FOAM Warning : 
    From function Foam::vector Foam::cellModel::centre(const labelList&, const pointField&) const
    in file meshes/meshShapes/cellModel/cellModel.C at line 70
    zero or negative pyramid volume: -1.25 for face 3
--> FOAM Warning : 
    From function Foam::vector Foam::cellModel::centre(const labelList&, const pointField&) const
    in file meshes/meshShapes/cellModel/cellModel.C at line 70
    zero or negative pyramid volume: -3.75 for face 4
#0  Foam::error::printStack(Foam::Ostream&) at ??:?
#1  Foam::sigFpe::sigHandler(int) at ??:?
#2  ? in "/lib/x86_64-linux-gnu/libc.so.6"
#3  Foam::blockDescriptor::check(Foam::Istream const&) at ??:?
#4  Foam::blockDescriptor::blockDescriptor(Foam::dictionary const&, int, Foam::Field<Foam::Vector<double> > const&, Foam::PtrList<Foam::blockEdge> const&, Foam::PtrList<Foam::blockFace> const&, Foam::Istream&) at ??:?
#5  Foam::block::block(Foam::dictionary const&, int, Foam::Field<Foam::Vector<double> > const&, Foam::PtrList<Foam::blockEdge> const&, Foam::PtrList<Foam::blockFace> const&, Foam::Istream&) at ??:?
#6  Foam::block::New(Foam::dictionary const&, int, Foam::Field<Foam::Vector<double> > const&, Foam::PtrList<Foam::blockEdge> const&, Foam::PtrList<Foam::blockFace> const&, Foam::Istream&) at ??:?
#7  void Foam::PtrList<Foam::block>::read<Foam::block::iNew>(Foam::Istream&, Foam::block::iNew const&) at ??:?
#8  Foam::blockMesh::createTopology(Foam::IOdictionary const&, Foam::word const&) at ??:?
#9  Foam::blockMesh::blockMesh(Foam::IOdictionary const&, Foam::word const&) at ??:?
#10  ? in "/apps/OpenFOAM/7.0/OpenFOAM-7/platforms/linux64GccDPInt32Opt/bin/blockMesh"
#11  __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6"
#12  ? in "/apps/OpenFOAM/7.0/OpenFOAM-7/platforms/linux64GccDPInt32Opt/bin/blockMesh"
Floating point exception

Could somebody help me figure out why? Many thanks in advance.

blockMeshDict:

/*--------------------------------*- C++ -*----------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     | Website:  https://openfoam.org
    \\  /    A nd           | Version:  7  
     \\/     M anipulation  |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      blockMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

convertToMeters 0.01;

vertices
(
    (-10      0       -0.5)
    (-10      3       -0.5)
    (0        3       -0.5)
    (10       3       -0.5)
    (10      -3       -0.5)
    (0       -3       -0.5)
    (0        0       -0.5)

    (-10      0        0.5)
    (-10      3        0.5)
    (0        3       -0.5)
    (10       3        0.5)
    (10      -3        0.5)
    (0       -3        0.5)
    (0        0        0.5)

);

blocks
(
    hex (0 1 2 6 13 9 8 7) (20 6 1) simpleGrading (1 1 1)
    hex (1 2 5 4 7 8 11 10) (20 12 1) simpleGrading (1 1 1)
);

edges
(
);

boundary
(
    flow
    {
        type patch;
        faces
        (
            (0 1 8 9)
            (3 4 12 11)
            (4 5 13 12)
        );
    }
    obstacle
    {
        type wall;
        faces
        (
            (0 7 15 8)
            (6 7 15 14)
            (5 6 14 13)
            (2 3 11 10)
            (1 2 10 9)
        );
    }
    frontAndBack
    {
        type empty;
        faces
        (
            (0 1 2 7)
            (2 3 4 7)
            (4 5 6 7)
            (8 9 10 15)
            (10 11 12 15)
            (12 13 14 15)
        );
    }
);

mergePatchPairs
(
);

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