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Supercavitation / overPimpleDyMFoam

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Old   August 18, 2021, 06:50
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  #21
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Yann
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Hi Senel,

I have no experience with cavitation so I can only point out the solver you could potentially use, but I never used any of these myself.

There is a solver dedicated to cavitation problems which can handle dynamic mesh but not overset:
  • cavitatingDyMFoam.

As for the current latest release (OpenFOAM-v2106), here is the list of the multiphase solvers with overset:
  • overCompressibleInterDyMFoam
  • overInterPhaseChangeDyMFoam
  • overInterDyMFoam
So I guess you need to find answers to these 2 questions:
  • Do you really need overset or can you use another dynamic mesh technique such as sliding mesh or morphing mesh?
  • Can you simulate cavitation with one of the current overset multiphase solver?
My best bet would be to go for overInterPhaseChangeDyMFoam since the solver description explicitly mention cavitation:

Code:
Description
    Solver for two incompressible, isothermal, immiscible fluids with
    phase-change (e.g. cavitation) using VOF (i.e. volume of fluid)
    phase-fraction based interface capturing, with optional dynamic mesh
    motion (including overset) and mesh topology changes including adaptive
    re-meshing.

    The momentum and other fluid properties are of the "mixture" and a
    single momentum equation is solved.

    The set of phase-change models provided are designed to simulate cavitation
    but other mechanisms of phase-change are supported within this solver
    framework.

    Turbulence modelling is generic, i.e. laminar, RAS or LES may be selected.

I hope this helps,
Yann
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Old   August 18, 2021, 15:38
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Senel Canik
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Hi Yann,

Thank you very much for your quick reply.

I use OpenFOAM-v2012. I will download and install v2106 as soon as possible to be able to use overInterPhaseChangeDyMFoam solver. It makes more sense to me for my cylinder case.

Another question:

Is it possible to give initial movement to floating object in X direction?

I have added velocity (20 0 0); function in DynamicMeshDict, but did not see any X movement. What do you think?

Regards,

Senel
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Old   August 19, 2021, 04:08
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Hi Senel,

Yes you can specify a displacement in the x direction (fixed displacement or initial condition), as long at the object is free to move in this direction, depending of the constraints applied in the sixDoF model.

By default in the floatingBody tutorial, there is a fixedLine contraint along the z axis so the object is not allowed to translate along the x or y axis.

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Yann
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Old   August 20, 2021, 10:05
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Senel Canik
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Hi Yann,

I removed fixedline constraint along Z axis and added velocity (500 0 0); line in dynamicMeshDict. Object moved and rotated freely. It seems there is no interaction with the water.

controlDict:
deltaT 0.00001;
endTime 0.002;
writeInterval 0.0001;

What do you think?
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Old   August 20, 2021, 11:02
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Hi Senel,


I think it's hard to have an opinion without seeing what result you get.


What do you mean by "no interaction with the water"?
And can you post your dynamicMeshDict?


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Old   August 20, 2021, 11:21
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Senel Canik
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Hi Yann,

Here is dynamicMeshDict file:

/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: v2106 |
| \\ / A nd | Website: www.openfoam.com |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
object dynamicMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

motionSolverLibs (sixDoFRigidBodyMotion);
dynamicFvMesh dynamicOversetFvMesh;
solver sixDoFRigidBodyMotion;
sixDoFRigidBodyMotionCoeffs
{
patches (floatingObject);
innerDistance 100.0;
outerDistance 101.0;
centreOfMass (0.5 0.5 0.3);
// Cuboid dimensions
Lx 0.24;
Ly 0.24;
Lz 0.4;
// Density of the solid
rhoSolid 700;
// Cuboid mass
mass #eval{ $rhoSolid*$Lx*$Ly*$Lz };
momentOfInertia (0.29 0.29 0.15);
velocity (500 0 0);
report on;
accelerationRelaxation 0.6;
accelerationDamping 0.9;
solver
{
type Newmark;
}
constraints
{
}
}


// ************************************************** *********************** //
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Old   August 20, 2021, 11:26
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Senel Canik
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"no interaction with the water":

while the floating object moves, there is no change on the surface of the water.
There is no color change inside or surface of water to indicate water-air mixture (alpha-water).
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Old   September 4, 2021, 10:52
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Senel Canik
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Hello Yann,

As you suggest, I have used overInterPhaseChangeDyMFoam solver for my cylinder in water application.

I could see the cavitation inside overset meshes but I dont see any cavitation in background meshes which is water in my case.

Do you have any suggestion to fix this?

Thank you and regards,

Senel
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Old   September 6, 2021, 11:07
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Hi Senel,


Isn't it related to mesh resolution in your background?
Do you have screenshots showing the issue ?


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