[okabis]

Hi everyone,

I am currently working on a simulation of a 6-DOF ship (body A) moving on a water surface with waves. This works perfectly fine so far.

Now I would like to add a box (body B), that is moving in the inside of the ship. So basically it can slide in one DOF on the floor inside the ship, depending on the movement of the ship induced by the waves and gravity (I'll add a sketch as picture).

Sadly, I am a little lost on how to implement this...

I started by creating a box geometry and turning it into a DOF body. My first thought was to tell the box to move like the ship and then have the possible x motion (in respect to the local coordinate system of the ship) as a DOF. I tried this by using superposing motions, but wasn't really able to implement it and am also uncertain, if this would even be correct...

My current attempt is to use a multi body motion in x direction (again with respect to a local coord system of the ship) together with a system of linear springs, to couple the two bodies.

I used a horizontal spring c1 and a vertical spring c2 (very stiff) between the box and the ship. For c2, I chose the coupling to lie way outside the ship geometry, so that a horizontal movement is still kinda possible (sketch is in attachments).

The results aren't satisfying at all...

Now I feel like there should be an easy way, to couple my two bodies, but I am unable to identify it...

The multibody motion with respect to a local ship coordinate system seems like the right start, but how do I tell the box to be "part of the ship"?

I could try to add the box as a region, with another overset mesh and real contacts, but that seems like complete overkill and insane rise of computational efforts.


So if anyone can help, it would be very much appreciated 🙂

Thanks in advance and have a nice day!