[KateEisenhower]

Hello,

I have some trouble with creating cyclic patches using createPatch and hope to find some help here.

I am simulating a wind tunnel flow with an airfoil which spans from the front to the back patch of the tunnel. It is a 3D case, but very similar to a 2D case because the mesh doesn't change in the y direction.

I created the mesh with gmsh and used gmshToFoam to get it working with OpenFoam 2.3.1. This works great so far.

Now the U_y Residuals are bothering me. I think they stay way to high and think this is related to the definition of my boundary codes front and back. Hence I want to try cyclic boundary condition on these two patches.

I got the default createPatchDict and set it up as follows (please note my questions in the first line of the code too):

pointSync false; // What does this mean?

// Patches to create.
patches
(
    {
        // Name of new patch
        name frontcy;

        // Dictionary to construct new patch from
        patchInfo
        {
            type cyclic;
            neighbourPatch backcy;

            // Optional: explicitly set transformation tensor.
            // Used when matching and synchronising points.
            // transform rotational;
            // rotationAxis (1 0 0);
            // rotationCentre (0 0 0);
            // transform translational;
            // separationVector (0 0.1 0);

            // Optional non-default tolerance to be able to define cyclics
            // on bad meshes
            matchTolerance 0.1;
        }

        constructFrom patches;

        patches (front); // front is my original front patch

    }
    {
        // Name of new patch
        name backcy;

        // Dictionary to construct new patch from
        patchInfo
        {
            type cyclic;
            neighbourPatch frontcy;

            // Optional: explicitly set transformation tensor.
            // Used when matching and synchronising points.
            // transform rotational;
            // rotationAxis (1 0 0);
            // rotationCentre (0 0 0);
            // transform translational;
            // separationVector (0 -0.1 0);
            matchTolerance 0.1;
        }

        constructFrom patches;

        patches (back); // back is my original back patch

    }
);

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

Does this file look right to you? I am particularly unsure about the section with the transformation tensor which is commented out. Do I need it, or what is it for? Do I need the matchTolerance option in my case?

When running createPatch in terminal I get the following. This is only the beginning of the output but I think you are getting the point. If necessary I can upload the complete output too.

Kates-MacBook-Pro:2D_hkverfeinert_cyclic kateeisenhower$ createPatch
/*---------------------------------------------------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.3.1                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
Build  : 2.3.1-262087cdf8db
Exec   : createPatch
Date   : Aug 31 2015
Time   : 12:24:50
Host   : "Kates-MacBook-Pro.local"
PID    : 91192
Case   : /Users/kateeisenhower/Documents/gmsh/Daten/2D_hkverfeinert_cyclic
nProcs : 1
sigFpe : Enabling floating point exception trapping (FOAM_SIGFPE).
fileModificationChecking : Monitoring run-time modified files using timeStampMaster
allowSystemOperations : Allowing user-supplied system call operations

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

Create polyMesh for time = 0

Reading createPatchDict

Adding new patch frontcy as patch 7 from 
{
    type            cyclic;
    neighbourPatch  backcy;
    matchTolerance  0.1;
}

Adding new patch backcy as patch 8 from 
{
    type            cyclic;
    neighbourPatch  frontcy;
    matchTolerance  0.1;
}


Moving faces from patch front to patch 7
Moving faces from patch back to patch 8

Doing topology modification to order faces.

Cannot find point in pts1 matching point 75283 coord:(-0.00588242 0.05 -0.0365509) in pts0 when using tolerance 0.000375467
Searching started from:0 in pts1
    Compared coord: (-0.00588281 0.05 -0.0392114) at index 0 with difference to point 0.00266053
    Compared coord: (-0.00588916 0.05 -0.0392308) at index 1 with difference to point 0.00267992
    Compared coord: (-0.00589583 0.05 -0.0392511) at index 2 with difference to point 0.0027003
    Compared coord: (-0.00590283 0.05 -0.0392725) at index 3 with difference to point 0.00272171
    Compared coord: (-0.00591018 0.05 -0.0392949) at index 4 with difference to point 0.00274421

Best regards,

Kate

[ykanani]

Hi, if your patches are not exactly identical, you cannot create Cyclic patch. use cyclicAMI instead.
please see this thread :
http://www.cfd-online.com/Forums/ope...port-icem.html

[PeterShi]

Originally Posted by KateEisenhower

Hello,

I have some trouble with creating cyclic patches using createPatch and hope to find some help here.

I am simulating a wind tunnel flow with an airfoil which spans from the front to the back patch of the tunnel. It is a 3D case, but very similar to a 2D case because the mesh doesn't change in the y direction.

I created the mesh with gmsh and used gmshToFoam to get it working with OpenFoam 2.3.1. This works great so far.

Now the U_y Residuals are bothering me. I think they stay way to high and think this is related to the definition of my boundary codes front and back. Hence I want to try cyclic boundary condition on these two patches.

I got the default createPatchDict and set it up as follows (please note my questions in the first line of the code too):

pointSync false; // What does this mean?

// Patches to create.
patches
(
    {
        // Name of new patch
        name frontcy;

        // Dictionary to construct new patch from
        patchInfo
        {
            type cyclic;
            neighbourPatch backcy;

            // Optional: explicitly set transformation tensor.
            // Used when matching and synchronising points.
            // transform rotational;
            // rotationAxis (1 0 0);
            // rotationCentre (0 0 0);
            // transform translational;
            // separationVector (0 0.1 0);

            // Optional non-default tolerance to be able to define cyclics
            // on bad meshes
            matchTolerance 0.1;
        }

        constructFrom patches;

        patches (front); // front is my original front patch

    }
    {
        // Name of new patch
        name backcy;

        // Dictionary to construct new patch from
        patchInfo
        {
            type cyclic;
            neighbourPatch frontcy;

            // Optional: explicitly set transformation tensor.
            // Used when matching and synchronising points.
            // transform rotational;
            // rotationAxis (1 0 0);
            // rotationCentre (0 0 0);
            // transform translational;
            // separationVector (0 -0.1 0);
            matchTolerance 0.1;
        }

        constructFrom patches;

        patches (back); // back is my original back patch

    }
);

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

Does this file look right to you? I am particularly unsure about the section with the transformation tensor which is commented out. Do I need it, or what is it for? Do I need the matchTolerance option in my case?

When running createPatch in terminal I get the following. This is only the beginning of the output but I think you are getting the point. If necessary I can upload the complete output too.

Kates-MacBook-Pro:2D_hkverfeinert_cyclic kateeisenhower$ createPatch
/*---------------------------------------------------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.3.1                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
Build  : 2.3.1-262087cdf8db
Exec   : createPatch
Date   : Aug 31 2015
Time   : 12:24:50
Host   : "Kates-MacBook-Pro.local"
PID    : 91192
Case   : /Users/kateeisenhower/Documents/gmsh/Daten/2D_hkverfeinert_cyclic
nProcs : 1
sigFpe : Enabling floating point exception trapping (FOAM_SIGFPE).
fileModificationChecking : Monitoring run-time modified files using timeStampMaster
allowSystemOperations : Allowing user-supplied system call operations

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

Create polyMesh for time = 0

Reading createPatchDict

Adding new patch frontcy as patch 7 from 
{
    type            cyclic;
    neighbourPatch  backcy;
    matchTolerance  0.1;
}

Adding new patch backcy as patch 8 from 
{
    type            cyclic;
    neighbourPatch  frontcy;
    matchTolerance  0.1;
}


Moving faces from patch front to patch 7
Moving faces from patch back to patch 8

Doing topology modification to order faces.

Cannot find point in pts1 matching point 75283 coord:(-0.00588242 0.05 -0.0365509) in pts0 when using tolerance 0.000375467
Searching started from:0 in pts1
    Compared coord: (-0.00588281 0.05 -0.0392114) at index 0 with difference to point 0.00266053
    Compared coord: (-0.00588916 0.05 -0.0392308) at index 1 with difference to point 0.00267992
    Compared coord: (-0.00589583 0.05 -0.0392511) at index 2 with difference to point 0.0027003
    Compared coord: (-0.00590283 0.05 -0.0392725) at index 3 with difference to point 0.00272171
    Compared coord: (-0.00591018 0.05 -0.0392949) at index 4 with difference to point 0.00274421

Best regards,

Kate

Hi Kate,

I met the exactly same problem as you, have you solved your problem yet? Thanks.

Best regards,
Peter

[clapointe]

As mentioned previously, cyclicAMI patches are needed if the patches do not match exactly. I've used the following createPatchDict before to create cyclicAMI patches :

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  4.x                                   |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      createPatchDict;
}

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

// This application/dictionary controls:
// - optional: create new patches from boundary faces (either given as
//   a set of patches or as a faceSet)
// - always: order faces on coupled patches such that they are opposite. This
//   is done for all coupled faces, not just for any patches created.
// - optional: synchronise points on coupled patches.

// 1. Create cyclic:
// - specify where the faces should come from
// - specify the type of cyclic. If a rotational specify the rotationAxis
//   and centre to make matching easier
// - always create both halves in one invocation with correct 'neighbourPatch'
//   setting.
// - optionally pointSync true to guarantee points to line up.

// 2. Correct incorrect cyclic:
// This will usually fail upon loading:
//  "face 0 area does not match neighbour 2 by 0.0100005%"
//  " -- possible face ordering problem."
// - in polyMesh/boundary file:
//      - loosen matchTolerance of all cyclics to get case to load
//      - or change patch type from 'cyclic' to 'patch'
//        and regenerate cyclic as above


// Do a synchronisation of coupled points after creation of any patches.
// Note: this does not work with points that are on multiple coupled patches
//       with transformations (i.e. cyclics).
pointSync false;

// Patches to create.
patches
(
    { 
        name c1;
        patchInfo
        {
            type            cyclicAMI;
            neighbourPatch  c2;
            
            // Optional: explicitly set transformation tensor.
            // Used when matching and synchronising points.
             transform rotational;
             rotationAxis (0 1 0);
             rotationCentre (0 0 0);
            // transform translational;
            // separationVector (0 0.1 0);

            // Optional non-default tolerance to be able to define cyclics
            // on bad meshes
            matchTolerance 0.1;
        }
        constructFrom patches;
        patches (t1);
        
    }
    
    { 
        name c2;
        patchInfo
        {
            type            cyclicAMI;
            neighbourPatch  c1;

            // Optional: explicitly set transformation tensor.
            // Used when matching and synchronising points.
             transform rotational;
             rotationAxis (0 1 0);
             rotationCentre (0 0 0);
            // transform translational;
            // separationVector (0 0.1 0);

            // Optional non-default tolerance to be able to define cyclics
            // on bad meshes
            matchTolerance 0.1;
        }
        constructFrom patches;
        patches (t2);
        
    }
);

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

I used the transform/rotational options because I was meshing a quarter of a cylinder -- they may not be necessary.

Caelan