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A liquid hitting a wall in a container will cause sloshing. The free surface effect is a mechanism which can cause a watercraft to become unstable and capsize. [1]It refers to the tendency of liquids — and of unbound aggregates of small solid objects, like seeds, gravel, or crushed ore, whose behavior approximates that of liquids — to move in response to changes in the attitude of a craft ...
The loss of stability from flooding may be due in part to the free surface effect. Water accumulating in the hull usually drains to the bilges, lowering the center of gravity and actually increasing the metacentric height. This assumes the ship remains stationary and upright.
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.
A surface effect ship (SES) or sidewall hovercraft is a watercraft that has both an air cushion, like a hovercraft, and twin hulls, like a catamaran.When the air cushion is in use, a small portion of the twin hulls remains in the water.
This includes information on precautions against capsizing, metacentric heights (GM), righting levers (GZ), rolling criteria, Free surface effect and watertight integrity. [1] The 2008 version of the Code details guidelines on Second Generation Intact Stability for ships, specifically criteria for dynamic stability and damage assessment. [7]
The resulting free surface effect destroyed her stability. [18] In a matter of seconds, the ship began to list 30 degrees to port. [19] The ship briefly righted herself before listing to port once more, this time capsizing. [19] The entire event took place within 90 seconds. [20]
Water sloshing on the vehicle deck can set up a free surface effect, making the ship unstable and causing it to capsize. Free surface water on the vehicle deck was determined by the court of inquiry to be the immediate cause of the 1968 capsize of the TEV Wahine in New Zealand. [7] It also contributed to the wreck of MS Estonia.
Important examples include propellant slosh in spacecraft tanks and rockets (especially upper stages), and the free surface effect (cargo slosh) in ships and trucks transporting liquids (for example oil and gasoline). However, it has become common to refer to liquid motion in a completely filled tank, i.e. without a free surface, as "fuel slosh".