Free Surface Effect
Further information: Free surface effectIn tanks or spaces that are partially filled with a fluid or semi-fluid (fish, ice, or grain for example) as the tank is inclined the surface of the liquid, or semi-fluid, stays level. This results in a displacement of the centre of gravity of the tank or space relative to the overall centre of gravity. The effect is similar to that of carrying a large flat tray of water. When an edge is tipped, the water rushes to that side, which exacerbates the tip even further.
The significance of this effect is proportional to the square of the width of the tank or compartment, so two baffles separating the area into thirds will reduce the displacement of the centre of gravity of the fluid by a factor of 9. This is of significance in ship fuel tanks or ballast tanks, tanker cargo tanks, and in flooded or partially flooded compartments of damaged ships. Another worrying feature of free surface effect is that a positive feedback loop can be established, in which the period of the roll is equal or almost equal to the period of the motion of the centre of gravity in the fluid, resulting in each roll increasing in magnitude until the loop is broken or the ship capsizes.
This has been significant in historic capsizes, most notably the MS Herald of Free Enterprise and the MS Estonia.
Read more about this topic: Metacentric Height
Famous quotes containing the words free, surface and/or effect:
“Most men, even in this comparatively free country, through mere ignorance and mistake, are so occupied with the factitious cares and superfluously coarse labors of life that its finer fruits cannot be plucked by them. Their fingers, from excessive toil, are too clumsy and tremble too much for that.”
—Henry David Thoreau (1817–1862)
“We’ve forgotten what it’s like not to be able to reach the light switch. We’ve forgotten a lot of the monsters that seemed to live in our room at night. Nevertheless, those memories are still there, somewhere inside us, and can sometimes be brought to the surface by events, sights, sounds, or smells. Children, though, can never have grown-up feelings until they’ve been allowed to do the growing.”
—Fred Rogers (20th century)
“At first I intended to become a student of the Senate rules and I did learn much about them, but I soon found that the Senate had but one fixed rule, subject to exceptions of course, which was to the effect that the Senate would do anything it wanted to do whenever it wanted to do it.”
—Calvin Coolidge (1872–1933)