While using the hack to use the file system and by adding the sphere (named "oggetto") to the "noModificationPatches" and "noSwapPatches", it does allow to keep the sphere's surface in perfect condition while it moves.
The downside is that it crashes when the cells in the way start to get too tight and eventually collapse into negative volumes.

The error message:

Code:

---

Courant Number mean: 0.04541765902 max: 4.191785362
deltaT = 3.333333333e-05
Time = 0.0202

sixDoFRigidBodyMotion constraints converged in 1 iterations
Constraint force: (0.6537136637 0.02252467437 0)
Constraint moment: (0 0 0)
Centre of mass: (-1.842749434e-08 1.08451596e-08 0.2001177404)
Linear velocity: (-0.0004352669538 8.108849543e-05 0.04280597798)
Angular velocity: (1.573833728 -1.569414796 -0.03449086776)

************** QualityAssessor(free only) Summary **************

  Evaluating quality for 72216 free elements of 72375 total elements.
  THERE ARE 1 INVERTED ELEMENTS.
  (Elements invalid at 1 of 72216 sample locations.)

  1 OF 72216 ENTITIES EVALUATED TO AN UNDEFINED VALUE FOR AspectRatioGamma

          metric    minimum    average        rms    maximum    std.dev.
AspectRatioGamma 1.002851198  15.115086 3721.202667    1000000 3721.171969

 Warning: Minimum cell quality is: -0.07980588317 at cell: 68575

 ~~~ Mesh Quality Statistics ~~~
 Min: -0.07980588317
 Max: 0.9981037065
 Mean: 0.8637096283
 Cells: 72375
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~



--> FOAM FATAL ERROR:
Encountered negative cell-quality!
Edge: 89295: (3253 3261)
vertexHull: 5(227 9861 10215 9856 3297)
Minimum Quality: -0.07980588317

    From function scalar dynamicTopoFvMesh::computeMinQuality(const label eIndex, labelList& hullVertices) const
    in file edgeSwap.C at line 2246.

FOAM aborting

#0  Foam::error::printStack(Foam::Ostream&) in "/home/bmss/OpenFOAM/OpenFOAM-2.1.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#1  Foam::error::abort() in "/home/bmss/OpenFOAM/OpenFOAM-2.1.x/platforms/linux64GccDPOpt/lib/libOpenFOAM.so"
#2  Foam::dynamicTopoFvMesh::computeMinQuality(int, Foam::List<int>&) const in "/home/bmss/OpenFOAM/bmss-2.1.x/platforms/linux64GccDPOpt/lib/libdynamicTopoFvMesh.so"
#3  Foam::dynamicTopoFvMesh::swap3DEdges(void*) in "/home/bmss/OpenFOAM/bmss-2.1.x/platforms/linux64GccDPOpt/lib/libdynamicTopoFvMesh.so"
#4  Foam::dynamicTopoFvMesh::threadedTopoModifier() in "/home/bmss/OpenFOAM/bmss-2.1.x/platforms/linux64GccDPOpt/lib/libdynamicTopoFvMesh.so"
#5  Foam::dynamicTopoFvMesh::update() in "/home/bmss/OpenFOAM/bmss-2.1.x/platforms/linux64GccDPOpt/lib/libdynamicTopoFvMesh.so"
#6 
 in "/home/bmss/OpenFOAM/OpenFOAM-2.1.x/platforms/linux64GccDPOpt/bin/pimpleDyMFoam"
#7  __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6"
#8 
 in "/home/bmss/OpenFOAM/OpenFOAM-2.1.x/platforms/linux64GccDPOpt/bin/pimpleDyMFoam"
Aborted (core dumped)

---

The "dynamicMeshDict":

Code:

---

/*--------------------------------*- C++ -*----------------------------------*\
| =========                |                                                |
| \\      /  F ield        | OpenFOAM Extend Project: Open Source CFD        |
|  \\    /  O peration    | Version:  1.6-ext                              |
|  \\  /    A nd          | Web:      www.extend-project.de                |
|    \\/    M anipulation  |                                                |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version    2.0;
    format      ascii;
    class      dictionary;
    location    "constant";
    object      dynamicMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

//- Select the type of dynamicFvMesh
dynamicFvMesh          dynamicTopoFvMesh;

//- Select the type of motionSolver
motionSolverLibs ("libmesquiteMotionSolver.so" "libfvMotionSolvers.so");
solver                  mesquiteMotionSolver;

mesquiteOptions
{
    usePointDisplacement yes;
 
    //- Optimization metric
    optMetric              AspectRatioGamma;

    //- Objective function
    objFunction            LPtoP;

    //- Optimization algorithm
    optAlgorithm            FeasibleNewton;

    //- Termination criteria sub-dictionaries
    //- (takes default values if not specified)
    //-  Specifying an empty sub-dictionary
    //-  terminates with available options
    tcInner
    {
        absGradL2            1e-4;
        cpuTime              0.5;
        // lele: iterationLimit 10;
    }

    // tcOuter
    // {}

    //- For composite functions, two objectives need to be specified
    // firstFunction          LPtoP;
    // secondFunction          LInf;

    //- For scaled functions, scale and objective needs to be specified
    // scaleFunction        PMeanP;
    // scale                1.5;

    //- Power value for the LPtoP objective function
    pValue                  2;
    power                  2;

    //- Specify a tolerance for the surface-smoothing CG solver
    tolerance              1e-2;

    //- Specify number of CG sweeps for surface-smoothing
    nSweeps                2;

    //- Specify slip patches for the motionSolver
    slipPatches
    {
        //wall;
        //oggetto;
    }

    //- Constrain surface mesh-motion on a specified cylinder
    cylindricalConstraints
    {
        //- Specify options per slip patch
    //    sideWall
    //    {
    //        axisPoint      (0.0 0.0 0.0);
    //        axisVector    (0.0 0.0 1.0);
    //        radius          1.0;
    //    }
    }

    //- Specify fixedValue patches for the motionSolver
    fixedValuePatches
    {
      oggetto
      {
          type            sixDoFRigidBodyDisplacement;
          centreOfMass    (0 0 0.2);
          momentOfInertia (0.000001 0.000001 0.000001);
          mass            0.01;
          rhoName        rhoInf;
          rhoInf          1000;  // needed only for solvers solving for kinematic pressure
          report          on;
          value          uniform (0 0 0);
          constraints
          {
            maxIterations 500000000;
            fixedLine1
            {
              sixDoFRigidBodyMotionConstraint fixedLine;
              tolerance 1e-6;
              relaxationFactor 0.7;
              fixedLineCoeffs
              {
                refPoint (0 0 0.2);
                direction (0 0 1);
              }
            }
          }
      }
    }
   
    //Other fixedValuePatch types can be found here:
    //src/dynamicMesh/meshMotion/fvMotionSolver/pointPatchFields/derived
   
    // angularOscillatingDisplacement
    // angularOscillatingVelocity
    // oscillatingDisplacement
    // oscillatingVelocity
    // surfaceDisplacement
    // surfaceSlipDisplacement

    //- Specify interval for surface smoothing
    surfInterval            1;
}

//- Options for dynamicTopoFvMesh
dynamicTopoFvMesh
{
    //- Should all options be made mandatory?
    //- Useful for first-time use.
    allOptionsMandatory no;

    //- Set run-time debug level [0-5]
    //debug              2;

    //- Specify the number of threads
    threads            1;

    //- Specify re-meshing interval
    //- Negative value implies no re-meshing
    interval            1;

    //- Specify whether the length-scale field
    //- should be dumped to disk
    dumpLengthScale    false;

    //- sliverThreshold specifies the
    //- quality criteria for sliver removal.
    sliverThreshold    0.35;

    //- Should the tool attempt to remove slivers
    //- that fall below the sliverThreshold value?
    removeSlivers      true;

    //- Skip mapping step. Useful while using
    //- this tool as a pre-processor
    // skipMapping        true;

    // Toggle edgeRefinement on/off
    edgeRefinement      no;

    //- Options for edge-bisection/collapse.
    //-  The edgeRefinement flag must be set for
    //-  the following options to have effect
    refinementOptions
    {
        collapseRatio  0.5;
        bisectionRatio  1.5;
        growthFactor    1.0;

        //- By default, existing boundary edge-lengths
        //- are used for length-scales.
        //- Length-scale can be fixed for certain patches.
        fixedLengthScalePatches
        {
            oggetto    0.2;
        }

        //- Avoid refinement on certain patches, if necessary
        noModificationPatches
        {
            inlet;
            outlet;
            wall;
            oggetto;
        }

        FreeSurfacePatch
        {
            oggetto;
        }
       
       
        //- Set floating length-scale values on certain patches
        freeLengthScalePatches
        {
            inlet;
            outlet;
            wall;
        }

        //- Limit lengthScales to specified values, if necessary
        // minLengthScale  0.1;
        // maxLengthScale  0.3;

        //- Field-based refinement options
        // fieldRefinement  gamma;
        // fieldLengthScale 0.005;
        // lowerRefineLevel 0.001;
        // upperRefineLevel 0.999;
        // maxRefineLevel  4;
        // meanScale        0.015;
    }

    //- If the number of modifications are to be limited, set this option
    // maxModifications  1000;

    //- Load custom libraries for metrics
    // tetMetricLibs      ("libtetMetrics.so");

    //- Tetrahedral mesh quality metric
    tetMetric          Knupp;

    //- Avoid 2-2 swapping on certain patches
    noSwapPatches
    {
      oggetto;
    }
}

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

---

Attached are the two images that show the initial position and the final position nearly before the crash, due to a collapsed cell.

I still haven't been able to make the proper update to work. I've tried to use the following code, but without success (this is the patch for the code):

Code:

---

----------------- mesquiteMotionSolver/mesquiteMotionSolver.C -----------------
index 468be60..a482416 100644
@@ -4738,6 +4738,18 @@ void mesquiteMotionSolver::update(const mapPolyMesh& mpm)
        Info<< "Clearing out mesquiteMotionSolver for topo-changes" << endl;
    }
 
+    // pointMesh
+    if (Mesh_.thisDb().foundObject<pointMesh>(pointMesh::typeName))
+    {
+        const_cast<pointMesh&>
+        (
+            Mesh_.thisDb().lookupObject<pointMesh>
+            (
+                pointMesh::typeName
+            )
+        ).updateMesh(mpm);
+    }
+
    motionSolver::updateMesh(mpm);
 
    if (surfaceSmoothing_)

---

The crash occurs just the same, namely whenever the "boundaryConditions_()" are accessed after the mesh has been changed.

• Force points to move:
  Code:

  ---

      const_cast<pointMesh&>(boundaryConditions_().mesh())
        .movePoints(Mesh_.points());

  ---

• Force an update of the mesh:
  Code:

  ---

      const_cast<pointMesh&>(boundaryConditions_().mesh())
        .updateMesh(mpm);

  ---