How to simulate changing CG/CB
 

Hi,

I am trying to simulate the motion of an underwater vehicle that has a varying Center of Gravity and a varying Center of Buoyancy. The variation occurs when the vehicle reaches a particular depth (for ex, at 0.5m depth, the CG moves forward, and CB moves back). As a consequence of these changes, the vehicle moves in a roughly sinusoidal pattern.

Does anyone if this can be modeled in Star CCM+? Specifically, how to model a varying CG/CB, and the consequential motion? Would be deeply grateful for any help.

VKS

You would need to use the rigid body "6-DOF Model" to do this. You could vary the model's CoG with time using a field function or a user macro.

To change the CoB you'll need to omit the gravity model (no hydrostatic pressure variation in the water column) and instead have user-defined external force that changes with time to reflect the desired CoB location and the proper orientation (always up in the inertial frame).