# DynamicMesh for Fish Motion

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November 6, 2020, 05:34
DynamicMesh for Fish Motion
#1
New Member

Shin Gyu Sik
Join Date: Mar 2020
Posts: 2
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Hi guys,

I'm analysising the fish motion. I using dynamicMesh method for describe the wavy motion, and modifying the existing 'angularOsillatingDisplacement'.

But there was an error during the dynamicMesh process. The end of fish tail point across the other cells. Why this happened?

The tutorial of Chalmers(http://www.tfd.chalmers.se/~hani/kur...h_openfoam.pdf) works great. The only thing changed is motion equations.

Fish motion is described well, but neighborhood point of tail end is not moving equal displacement of tail end. So tail end point interfere neighborhood cells.

The modified angularOsillatingDisplacement file such as:

Code:
```void my_angularOscillatingDisplacementPointPatchVectorField::updateCoeffs()
{
if (this->updated())
{
return;
}

const polyMesh& mesh = this->internalField().mesh()();
const Time& t = mesh.time();
scalarField Xcoord(patch().localPoints().component(vector::X));
scalar a2(1.0);

scalarField angle = angle0_ + amplitude_*(pi/180)*sin(2*pi*((1/waveLength_)*Xcoord - (1/period_)*t.value()));
vector axisHat = axis_/mag(axis_);
vectorField p0Rel(p0_ - origin_);

vectorField::operator=
(
p0Rel*(cos(angle) - 1)
+ (axisHat ^ p0Rel*sin(angle))
+ (axisHat & p0Rel)*(1 - cos(angle))*axisHat
);

fixedValuePointPatchField<vector>::updateCoeffs();
}```
The pointDisplacement file such as:

Code:
```    FISH
{
type my_angularOscillatingDisplacement;

origin (0 0 0);
value uniform (0 0 0);
axis (0 0 1);
angle0 0;
amplitude 10;
period 0.1;
waveLength 0.8;

}```
The dynamicMeshDict file such as:

Code:
```dynamicFvMesh dynamicMotionSolverFvMesh;

motionSolverLibs ("libfvMotionSolvers.so");

motionSolver displacementLaplacian;

The tail end point across the neighborhood cells such as:
Attached Images
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