Damaged stability with buoyancy aids

 Hello!

I'm doing some work on buoyancy airbags to regain buoyancy in damaged compartments and I'm struggling to find the best way to model them. 

A damaged compartment with a lower permeability ends up with the buoyancy lost and only reduces the water amount inside.

If I model it with a partial flood, I have a large amount of free surface because the water is moving around freely.

If I split the tank into many layers from bottom to top, I will have to configure the damaged cases, room definition, and load definition for each case. Although it seems to be the best approach, it will take a large amount of time and I must ignore the water between the airbags and the structure of the ship, again because of free surfaces.

Is there any better way to deal with this? I can't model a tank inside of another tank, right?

The use of empty damaged tanks is also a bit confusing to me. If I have some full tanks, let say ballast tanks or fuel tanks, I may want to have this option enable to simulate the fluid coming down to the water level and/or changing the density?  

The picture represents one section of the ship damaged tanks.

Thank you so much for your time

Adriano 

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  • hi Im not really sure what you are trying to model -- you are putting an air bag into a damaged tank and filling it with air, this reducing the volume that is flooded?

    If you want to do damage by lost buoyancy, I would simply reduce the size of the damaged tank/compartment in the Room definition table so that the part that is filled with an air bag is removed from the damage.

    An alternative method using added mass approach, would be to leave the tank intact, but fil it with seawater in the loadcase, you can manually specify a free-surface moment if you need to.

    The "empty damaged tanks" option is because some authorities require that liquid cargo originally in the tank before damage is still included in the loadcase, even though the tank is damaged and it's buoyancy removed. If you select "empty damaged tanks" , then they are removed from the loadcase; if not they are included in the loadcase

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  • hi Im not really sure what you are trying to model -- you are putting an air bag into a damaged tank and filling it with air, this reducing the volume that is flooded?

    If you want to do damage by lost buoyancy, I would simply reduce the size of the damaged tank/compartment in the Room definition table so that the part that is filled with an air bag is removed from the damage.

    An alternative method using added mass approach, would be to leave the tank intact, but fil it with seawater in the loadcase, you can manually specify a free-surface moment if you need to.

    The "empty damaged tanks" option is because some authorities require that liquid cargo originally in the tank before damage is still included in the loadcase, even though the tank is damaged and it's buoyancy removed. If you select "empty damaged tanks" , then they are removed from the loadcase; if not they are included in the loadcase

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