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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 ...
Flatness refers to the shape of a liquid's free surface. On Earth, the flatness of a liquid is a function of the curvature of the planet, and from trigonometry, can be found to deviate from true flatness by approximately 19.6 nanometers over an area of 1 square meter, a deviation which is dominated by the effects of surface tension.
Here σ is the surface tension, n, t and s are unit vectors in a local orthogonal coordinate system (n,t,s) at the free surface (n is outward normal to the free surface while the other two lie in the tangential plane and are mutually orthogonal). The indices 'l' and 'g' denote liquid and gas, respectively and K is the curvature of the free surface.
The range of positive stability will be reduced to the angle of down flooding resulting in a reduced righting lever. When the vessel is inclined, the fluid in the flooded volume will move to the lower side, shifting its centre of gravity toward the list, further extending the heeling force. This is known as the free surface effect.
Capsizing – Action where a vessel turns on to its side or is upside down; Free surface effect – Effect of liquids in slack tanks; Inclining test – Test to determine stability, lightship weight, and center of gravity of a ship; Kronan (ship) – Swedish Navy ship of the 1670s; Mary Rose – English Tudor warship (1511–1545)
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".
An illustration of fluid simulation using VOF method. In computational fluid dynamics, the volume of fluid (VOF) method is a family of free-surface modelling techniques, i.e. numerical techniques for tracking and locating the free surface (or fluid–fluid interface).
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]