What is meaning of centreOfMass, transform

kind9111 · October 15, 2020, 02:28

I'm solving tutorial DTCHull (interDyMFoam) in OF41.

But I don`t know "centreOfMass", "transfoam" in constant/dynamicMeshDict

Does anyone know what this means?

Krapf · October 16, 2020, 06:03

centreOfMass is the center of mass of the body in relation to the global coordinate system.

I can't help you with transform, but I found this post: User guide for dynamicMeshDict

kind9111 · October 16, 2020, 06:35

The contents of my dynamicMeshDict file are as follows.

dynamicFvMesh dynamicMotionSolverFvMesh;

motionSolverLibs ("librigidBodyMeshMotion.so");

solver rigidBodyMotion;

rigidBodyMotionCoeffs
{
report on;

solver
{
type Newmark;
}

accelerationRelaxation 0.4;

bodies
{
KVLCC2
{
type rigidBody;
parent root;

centreOfMass (0 0 0);
mass 155.929757471;
inertia (8.392763266119104 0 0 99.79504478144 0 99.79504478144);
transform (1 0 0 0 1 0 0 0 1) (0 0 -0.022);

joint
{
type composite;
joints
(
{
type Pz;
}
{
type Ry;
}
);
}

patches (KVLCC2);
innerDistance 0.3;
outerDistance 1;
}
}

restraints
{
translationDamper
{
type linearDamper;
body KVLCC2;
coeff 8596;
}

rotationDamper
{
type sphericalAngularDamper;
body KVLCC2;
coeff 11586;
}
}
}

My ship is KVLCC2 (scale 1:100). Lpp=3.2m, center of mass=(0, 0, -0.022)

I think the transform value and the centre of rotation value are the same.

But when written as above, the result value is wrong.

anyone knows what's wrong?

October 15, 2020, 02:28	What is meaning of centreOfMass, transform	#1
kind9111 New Member PikaBoo Join Date: Jan 2020 Posts: 2 Rep Power: 0	I'm solving tutorial DTCHull (interDyMFoam) in OF41. But I don`t know "centreOfMass", "transfoam" in constant/dynamicMeshDict Does anyone know what this means?

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October 16, 2020, 06:03		#2
Krapf Senior Member Join Date: Oct 2017 Posts: 133 Rep Power: 9	centreOfMass is the center of mass of the body in relation to the global coordinate system. I can't help you with transform, but I found this post: User guide for dynamicMeshDict

October 16, 2020, 06:35		#3
kind9111 New Member PikaBoo Join Date: Jan 2020 Posts: 2 Rep Power: 0	The contents of my dynamicMeshDict file are as follows. dynamicFvMesh dynamicMotionSolverFvMesh; motionSolverLibs ("librigidBodyMeshMotion.so"); solver rigidBodyMotion; rigidBodyMotionCoeffs { report on; solver { type Newmark; } accelerationRelaxation 0.4; bodies { KVLCC2 { type rigidBody; parent root; centreOfMass (0 0 0); mass 155.929757471; inertia (8.392763266119104 0 0 99.79504478144 0 99.79504478144); transform (1 0 0 0 1 0 0 0 1) (0 0 -0.022); joint { type composite; joints ( { type Pz; } { type Ry; } ); } patches (KVLCC2); innerDistance 0.3; outerDistance 1; } } restraints { translationDamper { type linearDamper; body KVLCC2; coeff 8596; } rotationDamper { type sphericalAngularDamper; body KVLCC2; coeff 11586; } } } My ship is KVLCC2 (scale 1:100). Lpp=3.2m, center of mass=(0, 0, -0.022) I think the transform value and the centre of rotation value are the same. But when written as above, the result value is wrong. anyone knows what's wrong?