I've been asked if I can animate the motion of a vessel in
the water given a time series file of heave, surge, sway, pitch,
roll, and yaw. I'm (almost) totally new to COSMOSMotion, and
probably need some extra help.
Anybody have some ideas?
Anybody have some ideas?
While I've done simple buoyancy, and have seen some models where people have represented wave motion, it is not a simple task.
There are several factors to account for:
1. Buoyancy forces
These really they need to be distributed along the structure if it has significant pitch or roll.
The calculation of the buoyancy force can be predetermined for a section of the vessel based on its volume below the water line (and weight mismatch). You need to measure the distance and apply the appropriate buoyancy force based on that.
If you don't break up the structure, then you need to characterize/calculate the net buoyancy of the vessel as a function of pitch & roll.
You can use CAD to calculate these by having a body of water as one solid and placing the vessel in different orientations and computing the net interfering volume.
2. Drag
Obviously there is significant resistance from water to movement through it, so again determining drag forces is really going to be an approximation, but I think it would be primarily in the yaw axis depending on vessel geometry.
Wind force may also play a role depending on area above the waterline and wind direction
So there is a bit of work in characterizing the vessel's response. Then applying certain conditions is just a matter of applying forces and moments to the vessel to represent the water condition. The method for this depends upon how you characterize the vessel response. If it is discretized, then the loads need to be sequenced along the sections. For example, if you split the vessel length into several sections, you need to have a phase offset on the pitch loading from the water along the length (to emulate the wave passing along the length).
I hope this helps give you some food for thought on what would be involved in modeling this.
The application I did was for a segmented wharf, where each section pretty much just rose up and down based on a wave coming through so it does not have the complexity of what you are looking at.
Cheers,
Ian