# pimpleDyMFoam - harmonic motion of a plate - wrong pressure distribution

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April 30, 2014, 08:28
pimpleDyMFoam - harmonic motion of a plate - wrong pressure distribution
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Dear all,

I am working on a plate with a simple harmonic motion. This plate is located in an entirely closed box full of water. It is an axisymmetric geometry.
By using pimpleDyMFoam solver and uncoupledSixDoFRigidBodyDisplacement on the plate in the pointDisplacement file I achieved to perform the simple harmonic motion of the plate.
A picture representing the geometry and the patches is enclosed.
I also enclosed my pointDisplacement and U files.
And here is my p file :

Code:
dimensions      [0 2 -2 0 0 0 0];

internalField   uniform 0;

boundaryField
{

down
{
}

up
{
}

fixedArcDown
{
}

fixedArcUp
{
}

movingArc
{
}

center
{
type symmetryPlane;
}

plate
{
}

frontAndBackPlanes_pos
{
type    wedge;

}

frontAndBackPlanes_neg

{
type   wedge;
}

}
The velocity comportment seems physical with eddies moving the way I expected (cf picture "Velocity" enclosed)

But for the pressure, my results are not correct. When the plate goes up, there is a depression on the top of the plate and an overpressure on the bottom of the plate... (you can see it on the "Pressure" picture enclosed)
And the same reversed illogical presure distribution occurs when the plate goes down.

At the previous step of my work, I made the plate moves only at an uniform velocity and the pressure distribution was totally fine.
So I guess the problem comes from the use of the uncoupledSixDoFRigidBodyDisplacement but I can't figure how to fix it to obtain a correct pressure distribution for the simple harmonic motion.

Does anyone has experienced this kind of pressure distribution problem with simple harmonic motion?

Attached Images
 Geometry.png (48.1 KB, 19 views) Pressure.png (88.7 KB, 16 views) Velocity.png (65.0 KB, 19 views)
Attached Files
 pointDisplacement.txt (3.7 KB, 9 views) U.txt (1.6 KB, 3 views)