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FPSO Roll motion

Hello everyone,

I'm trying to simulate a roll motion of an FPSO ship in order to find the moments acting on a hull to find the damping coeficients. Im trying to conduct a transient analysys of a 2D sinusoidal ship motion. My model setup is presented on an attached screenshot. The inner part of the domain is rotating in the sinusoidal fashion and the outer part stays still. The outer wall is made as an outlet and upper boundary is set as a free surface of water. My question is wether such setup is possible to execute in acusolve, or should I consider a bigger domain and try to execute the simulation as multiphase ? Im currently facing an error saying:

"Severe distortion in specified mesh; exit without updating"

(mesh deformation is disabled in the motion setup)

Thanks for your help.

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AcuSolve

English

HyperMesh CFD

v2022.3

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acupro

Might be good to see the input and Log files.

Can you also attach some sketches of the range of motion of the FPSO ship - and how you would want the water surface to appear as the ship moves? Are you trying to move just the ship surfaces and have the inner water 'adjust' as the surface moves? Are you trying to rotate the entire inner fluid region (including the ship) as a single piece - then what happens between inner and outer - etc?

AdamK

Might be good to see the input and Log files.

Can you also attach some sketches of the range of motion of the FPSO ship - and how you would want the water surface to appear as the ship moves? Are you trying to move just the ship surfaces and have the inner water 'adjust' as the surface moves? Are you trying to rotate the entire inner fluid region (including the ship) as a single piece - then what happens between inner and outer - etc?

Thanks for your reply, I'm trying to simulate the roll motion in a range of different amplitudes up to 15 degress. I was trying to rotate the entire inner fluid region and a ship as a single piece. I was trying to set up some kind of sliding mesh interface between them. Is such option possible within hyperworks CFD and acusolve ?

acupro

Thanks for your reply, I'm trying to simulate the roll motion in a range of different amplitudes up to 15 degress. I was trying to rotate the entire inner fluid region and a ship as a single piece. I was trying to set up some kind of sliding mesh interface between them. Is such option possible within hyperworks CFD and acusolve ?

I'm attaching some information from an old AcuConsole-based tutorial. That interface is no longer available for use - but maybe the ideas presented can help you get started.

So long as the motion isn't rapid, you can probably use the guide-surface concept for the fluid mesh to slide along the rolling solid. (The tutorial represents the 'hull' as two bars.) The lower portion of the mesh is a separate body that moves exactly with the rest of the hull, while the fluid above adjust to the shape of the upper hull and the free surface.

Roller_Tutorial_OLD.pdf

Rolling_Ship.avi