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Simulating Ship Motions caused by waves in STAR-CCM

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Old   August 6, 2014, 10:43
Post Simulating Ship Motions caused by waves in STAR-CCM
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Aitken Mitchell
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Hi guys,

I am a placement student at an Oil & Gas/ Renewables/ Marine company based in Scotland and I'm looking for a little help getting a project going that involves a ship designed at this company. I am planning to use this project for my final year dissertation, starting in September also. Firstly, I'd just like to say thank you for taking your time out to read my post, and also that I'm fairly new to this software but I'm very keen to get some experience under my belt.

So effectively, I am working on a project that involves a ship, which has to perform heavy lifting activities offshore using a crane. The ship is completely free floating (not a semi-submersible or jack-up).

In order to understand which sea states are safe to complete these lifting operations in, I want to model the simulation using CFD software and I have chosen STAR-CCM+ to do so after extensive research into these software packages. I have looked through many of the tutorials that are available for the software and have run through them on the student software - I have a rough understanding of the software's capabilities now.

The best tutorial I have completed is one on motion called: "DFBI boat in head waves", and this tutorial gave me a great idea how to model this kind of simulation after running through it a few times. I am currently modelling the ship hull that I wish to simulate in Rhino (which I will then convert to a parasolid before importing it into the simulation). The problem with this is that when I go to insert the parasolid into STAR-CCM+ as a surface mesh, it won't work and merely crashes the program. Any tips?

Also, I wish to use the JONSWAP function to produce a wave spectra and produce a set of RAO data (Remote Amplification Operators) which is the ship 6-DOF data that I can then use to work out a maximum movement in the crane of the vessel using moments. Is there a better way of doing this?

And one last thing, how can I change the direction of the waves on the ship, for instance if the ship were to have a heading of 000, then 015 with the waves moving in the same direction - I want to model this for different headings. How is this possible?

Sorry if this is a bit too much for one feed, any help is appreciated! Also please don't be afraid to completely change my plan in telling me how to best simulate this problem, I'm all ears.

Kind Regards,

Aitken Mitchell

Last edited by Aitken Mitchell; August 6, 2014 at 10:46. Reason: Noticed a little missing point.
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Old   August 8, 2014, 01:06
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What was the import error?

There are different types of VOF waves you can input, check them out in the user guide. I think one of them has some sort of spectrum function.

To change the direction of the waves, just change the vector your VOF waves are incoming from.
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Old   August 8, 2014, 04:29
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Well, when drawing the vessel I was trying to just loft a lines plan and I think it was too complex a file for STAR-CCM to open. I am using a surface meshing tool now and should have it completed soon, hopefully it will work this time.

I have had a look at the VOF options already - JONSWAP (Joint Offshore North Sea Wave Amplification Parameters) is available and is perfect for me as it is the North Sea I am modelling for.

I have been trying this also within the pre-built tutorial, I tried just playing about with the direction vector from [-1,0,0] to [-1,1,0] for instance but it was almost as if it split the simulation into two and made the waves come from the center out. When I entered certain wave heights it would also make the simulation mutate into strange shapes and screw up.

I played around with the timesteps and itterations etc also, could you point me in the direction of how to learn to assign the correct time scales?

Many Thanks,
Aitken
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Old   August 8, 2014, 05:07
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Also is there a way I could add another geometry into the simulation such as a pile or jacket and have it suspended from the vessel's crane?
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