Sinking

Good morning,

This is Pietro I was wondering if Moses is able to manage a sinking operation of a floating caisson like in the picture.

Basically, we can create an internal arrangement for ballasting and we can use guideposts/mooring lines to put in place the caisson.

The problem is that the waterplane area is drastically reducing (and GM as well), once the water is going on deck; furthermore, we need to stop the sinking at difference immersions before put it on the seabed.

 Do you think Moses could help us?

Thanks

Pietro

  • Hi Pietro,

    MOSES can help with designing the compartments, the ballast sequence, and the lowering lines.  You can perform parametric studies to determine the number of lines needed and the pretensions.   MOSES has been used in many project that involve partial submergence of a vessel.  In these projects there is an even where the water plane area is drastically reduced.  Usually when the main deck of the vessel is submerged.  MOSES has been used to design the ballast sequence so as to maintain a positive GM and lower the amount of time at the minimal GM values.

    I hope this helps.  Let me know if there are other questions.

    Georgina Maldonado

  • Hi Georgina,

    Many thanks for your replay, really appreciated.

    What I am really worried about, and I am so sorry if it was not clear, is the sinking velocity. If this velocity is excessive, the bottom of the caisson could bump the seabed and could be damaged. Furthermore, we should be able to stop the sinking process at 0.5m from the seabed to make the last seabed checking using the caisson ballast system. From some aspect, it's like a submarine.

    Do you think we can do that with Moses or maybe another Bentley software?

    Thanks again

    Pietro

  • Hi Pietro,

    For each compartment you will be able to define a valve.  You can open the valve and let water free flood in or you can attach a pump to the valve.  In both cases you will be able to use the flow rate to control the sinking velocity.  I assume you will be doing this in the time domain.  A standard report for the body is motions, velocities, and accelerations.  You can also ask for monitoring of designated points along the bottom of the caisson.  MOSES can alert you when any of the points reaches 0.5m from the seabed.  The alert can stop the simulation, change the status of a valve (open/close), or just a message to you.

    I hope this helps.  Let me know if there are other questions.

    Georgina Maldonado

  • Thanks a lot Georgina, this is very useful and clear.

    Have a nice day