[mecbertin]

Hi All,

I am hoping to get some suggestions for the OpenFOAM implementation of an overset mesh with deformable front mesh (e.g. using the displacementLaplacian solver).

I have seen this following presentation wrote about foam-extend 4.1 in November 2018:
https://foam-extend.fsb.hr/wp-conten...solid4Foam.pdf

In there, on slide 19, they are explaining "Front mesh deformation for FSI simulation", and how the mesh deformation is limited to the front mesh using subsetMotionSolverFvMesh.

I am finding foam-extend 4.1 challenging to understand compared to the traditional OpenFoam.
Would anyone have any suggestions for any material or course that could help me to set up/run my case (an overset mesh with deformable front mesh)?
Ideally, I would prefer to set up my case in OpenFOAM v1912. Would someone know what type of setup I should use with the overPimpleDyMfoam solver? Or any material or course that could help me with this?

Cheers,

Celia

[Michael@UW]

Hello Celia,
I am also interested in coupling overset with morphing. It seems we can use displacementLaplacian to deform the front body.

dynamicFvMesh       dynamicOversetFvMesh;

motionSolverLibs ( "libfvMotionSolvers.so" );

solver          displacementLaplacian;

displacementLaplacianCoeffs
{
    diffusivity     uniform 1;
}

But if I want to move the solid body (front) and deform the background patches at the same time. Do you know how to define the solid body motion at the same time in dynamicMeshDict?

Regards,
Michael

[louisgag]

This is old but we had the same problem here and I had to read the code a few times before we could get this working, so here's the heads up:


solidBodyDisplacementLaplacian and displacementLaplacian are not coded to support acting on different zones, so you have to split the solvers in your dynamicMeshDict as such:

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  v2006                                 |
|   \\  /    A nd           | Website:  www.openfoam.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      dynamicMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //



dynamicFvMesh       dynamicOversetFvMesh;
solvers
{
    c1Block
    {
        motionSolverLibs (fvMotionSolvers "libcontrolled6DoFMotion.so");
        motionSolver solidBody;
        cellZone c1;
        solidBodyMotionFunction  rotatingMotion;
                origin      (0.005 0.005 0.005);
                axis        (0 0 1);
                omega       10;
    }
 
 deformations
 {
     motionSolverLibs (fvMotionSolvers "libcontrolled6DoFMotion.so");
     motionSolver displacementLaplacian;
     diffusivity uniform 1;
 }

}




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

and keep in mind that setting a zone for the deformation part will not bring much...

[quarkz]

Hi louisgag,

my objective is simulate a plane with deforming folding wing which pitches up due to 6dof. i want the wing deformation to cause the front overset mesh to deform internally. I would like to use 6dof to determine its pitching response and cause the front mesh to rotate as a whole due to the pitching.

I tried using your dynamicMeshDict as a starting point. It seems that I can get internal mesh deformation of the front overset mesh due to the wing folding. However, OpenFOAM doesn't seem to allow the front mesh to pitch (whole mesh rotates without deformation) due to 6dof.

Is this so? Is there anyway to circumvent it? I have attached my pointDisplacement and dynamicMeshDict

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  v1912                                 |
|   \\  /    A nd           | Website:  www.openfoam.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       pointVectorField;
    object      pointDisplacement;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions      [0 1 0 0 0 0 0];

internalField   uniform (0 0 0);

boundaryField
{

	#includeEtc "caseDicts/setConstraintTypes"

	overset_p1
    {
        patchType       overset;
        type            zeroGradient;
    }


    wing
    {
    type        prototype_retract_motion;
    //type	myAngularOscillatingDisplacement;
	axis		(0 -1 0);
	origin (0.03 0 0.235);
	angle0		 0;
	amplitude       1.571;  //units of rad
	reverse_pitch   0;//0.7854;
    maximum_retract_angle 0.7854;
	omega           1.5708;       //units of rad/s
 	value           uniform (0 0 0); 
    }
    
    body_tail
    {
        type            calculated;
        value           uniform (0 0 0);
    }	

    ".*"
    {
        type            fixedValue;
        value           uniform (0 0 0);
    }
	

}


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

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

dynamicFvMesh       dynamicOversetFvMesh;

/*motionSolverLibs ( "libfvMotionSolvers.so" );

solver          displacementLaplacian;

displacementLaplacianCoeffs
{
    diffusivity     uniform 1;
    //diffusivity inverseDistance 1(wing|overset_p1|body_tail);
}

dynamicOversetFvMeshCoeffs
{
//    layerRelax 0.3;
}
*/

solvers
{
    sixdof_pitch
    {
        motionSolverLibs (sixDoFRigidBodyMotion);
        motionSolver sixDoFRigidBodyMotion;
        cellSet wing_body_tail;
        patches         (wing body_tail);
	    innerDistance   100.0;
	    outerDistance   101.0;
	
	    centreOfMass    (0. 0. 0.);
	    g               (0 -9.81 0);
	    velocity        (13.89 0. 0.);
	    rho             rhoInf;
		rhoInf          1.2;
	
	    // Cuboid mass
	    mass            1.6;
	
	    // Cuboid moment of inertia about the centre of mass
	    //momentOfInertia (0.028173316 0.047624436 0.073855382);
	    momentOfInertia (0.028173316 0.073855382 0.047624436);
	
	    report          on;
	    accelerationRelaxation 0.6;
	    accelerationDamping    0.9;
	
	    solver
	    {
	        type Newmark;
	    }
	
	    constraints
	    {
	
	        
	        fixedPoint
	        {
	             sixDoFRigidBodyMotionConstraint point;
	             centreOfRotation (0. 0. 0.);
	        }
	        
	
	        fixedAxis
	        {
	            sixDoFRigidBodyMotionConstraint axis;
	            axis (0 0 1);
	        }
	        
	    }
        
        
    }
 
    wing_deformations
 	{
     	motionSolverLibs (fvMotionSolvers);
		motionSolver displacementLaplacian;
		cellZone wing_body_tail;
		//diffusivity uniform 1;
		diffusivity inverseDistance 1(wing);
		//diffusivity quadratic inverseDistance 1(wing);
    }

}
// ************************************************************************* //

[louisgag]

Hi,
i don't have experience with the 6dof solver, but usually you have to project the pointDisplacement motion so that they match you rigid body motion.
Maybe you can find an example here: $FOAM_TUT/multiphase/compressibleInterDyMFoam/laminar/sphereDrop and try to adapt it overset...
Not sure I can help more than that, feel free to inspire yourself from python-based or MBDyn-based solutions:
https://darus.uni-stuttgart.de/datas...419/darus-2191

https://darus.uni-stuttgart.de/datas...419/darus-2232

[quarkz]

Hi louisgag,

Sure, thanks for the recommendations. I'll take a look.

[quarkz]

Hi everyone,

I'm now trying to run a simple test case to see if it works.

It consists of a background rectangle domain and a front cylinder overset mesh.

I want to test if it is possible to run a simulation such that the front cylinder overset mesh:

1. move entire overset mesh vertically up and down without deformation

and

2. move cylinder boundary vertically up and down with deformation. boundary of overset mesh is not moving.

I managed to get (1) working using the codes below but not (2). Objective is to do (1) + (2) together.

Is it possible?

I tried Michael@UW suggestions:

dynamicMeshDict

dynamicFvMesh       dynamicOversetFvMesh;

motionSolverLibs ( "libfvMotionSolvers.so" );

solver          displacementLaplacian;

displacementLaplacianCoeffs
{
    diffusivity     uniform 1;
}

pointDisplacement

boundaryField
{
    #includeEtc "caseDicts/setConstraintTypes"

    oversetPatch
    {
        patchType       overset;
        type            zeroGradient;
    }

    
	
	cyl
    {
        type            oscillatingDisplacement;
        amplitude       (0 0.5 0);
        omega           3.142;
        value           uniform (0 0 0);
    }


    ".*"
    {
        type            fixedValue;
        value		uniform    (0 0 0);
    }
}

I also tried louisgag's suggestions:

dynamicMeshDict

dynamicFvMesh       dynamicOversetFvMesh;

solvers          

{
	cylinder_overset
	{
        motionSolverLibs (fvMotionSolvers  "libcontrolled6DoFMotion.so");
		
		motionSolver            solidBody;
        solidBodyMotionFunction oscillatingLinearMotion;
		
		cellSet                 cyl_overset;
		oscillatingLinearMotionCoeffs
		{
			amplitude       (0.0 0.5 0.0);
			omega           6.2831853;//-0.7854;//-0.1745;    //5.52 rad/s
		}

        
    }
	
	deformations
 	{
     	motionSolverLibs (overset fvMotionSolvers  "libcontrolled6DoFMotion.so");
		motionSolver displacementLaplacian;
		diffusivity uniform 1;
		//diffusivity inverseDistance 1(cyl);
	}

}

pointDisplacement

boundaryField
{
    #includeEtc "caseDicts/setConstraintTypes"

    oversetPatch
    {
        patchType       overset;
        type            zeroGradient;
    }

    
	cyl
    {
        type            oscillatingDisplacement;
        amplitude       (0 0.5 0);
        omega           3.142;
        value           uniform (0 0 0);
    }


    ".*"
    {
        type            fixedValue;
        value		uniform    (0 0 0);
    }
}

Can anyone help?

Thanks

[Umut]

Hello,

I have a similar (if not same) problem.

Running an FSI simulation, similar with Hron-Turek FSI benchmark, flow induced thin beam deformation.

My problem is the boundary of the front mesh (overset surfaces) are not deforming.

The thin beam and the mesh around it is deforming just fine, however since the outer boundaries of front mesh (overset patches) are not moving, I had to use a very large front mesh domain size.

A second (and less important) problem is, the background mesh is deforming, too, which I prefer it to be stationary.

I couldn't figure out how to keep the background mesh stationary, while front mesh (especially including its boundaries) to deform with the thin beam.