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Simulating Moored Ships, Tug Boats, Offshore Platforms and Other Moving Objects

A new springs and ropes capability has been added to FLOW-3D's General Moving Objects model, the only one of its kind in commercial CFD softwares. Objects with coupled motion can be tethered by spring or ropes to other moving or stationary objects or to arbitrary fixed points in space. Several types of springs can be modeled such as expansion, compression and torsion springs.

In ocean engineering, users can study the stability of Floating Production, Storage, and Offloading (FPSO) systems. Motions of floating wave power generation systems, mooring of ship and marine measurement equipment and boat towing can also be simulated.

Below are examples of how the fluid-structure capabilities of the General Moving Object model can be applied to maritime design projects. Read more about modeling fluid structure interaction using FLOW-3D.

Simulating a Moored Ship Using Strings & Ropes Capability

This fluid structure interaction simulation depicts the motion of a moored ship under a wave condition. Six mooring lines are fixed to the deck of the vessel at one end, and fixed to the shore on the other end. A fifth-order Stokes wave is generated at the open boundary and propagates toward the ship. The animation shows the ship's motion caused by the wave and confined by both the tension force from the mooring lines and collisions on the dock wall.

 
Closeup look at the hawser
Close up of the hawser (see the Wikipedia definition).
Modeling the ropes in a ship mooring simulation

Placement of six ropes

Modeling Instability vs. Stability

These fluid structure interaction simulations demonstrate FLOW-3D's ability to capture and accurately couple the water motion with the ships buoyancy center, gravity center and metacentric heights. The unstable ship has a specifically modified gravity center to depict an unstable ship design.

More Fluid Structure Interaction Simulations

The fluid structure interaction simulation on the bottom left depicts a side launch of a warship from its building site. The slide of the ship with the slipway is treated as a series of micro-collisions and is simulated using the collision model. The floating of the ship is calculated with dynamic coupling with water motion.

The applications for the GMO model have expanded with every release. FLOW-3D Version 9.3 gave users the ability to model moving assemblies of components with different densities. In this example on the bottom right, a ship composed of two materials (lesser density in the fore; greater density in the aft) is being modeled.

 


FLOW-3D simulation of a side-launch of a warship.


FLOW-3D fluid structure interaction simulation of a
ship modeled with uneven density distribution.