`Demonstrates an air bubble in a flooding ballast tank with an air vent below
`the tank top. The pressure in the air is 1.0 atm when the water in the tank
`is at or below the vent. As the water rises further the pressure increases
`which keeps the water from rising to the outside level. The increase in
`air pressure is inversely proportional to the decrease in air volume.

proj bubble

`Make a simple hull with tanks:
enter pm
create hull
ends 0 100
out 10
top 10
bot 0
/
create tank1.c
ends 30 50
fit hull.c
/
create tank2.c
ends 50 70
fit hull.c
/
write bubble.gf
quit pm

`Establish light ship:
depth 5
vcg 5
solve weight, lcg


tank * `<-- selects all tanks
type bubble

`The point of flooding/venting is represented by the reference point:
ref top `Reference points at top
ref * * 6 `Now lower the vertical coordinate

`Since the tanks will not flood until the water level is at or above the
`reference points, we have to load them to that point explicitly. This
`also establishes the 1-atmosphere air volume:
load ref:0

`Now solve for equilibrium and report the status:
solve
status
load