Search results
Results from the WOW.Com Content Network
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 ...
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 surface energy of a liquid may be measured by stretching a liquid membrane (which increases the surface area and hence the surface energy). In that case, in order to increase the surface area of a mass of liquid by an amount, δA, a quantity of work, γ δA, is needed (where γ is the surface energy density of the liquid).
Damage stability calculations are much more complicated than intact stability. Software utilizing numerical methods are typically employed because the areas and volumes can quickly become tedious and long to compute using other methods. The loss of stability from flooding may be due in part to the free surface effect.
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".
Bubbles in pure water are unstable. The addition of surfactants, however, can have a stabilizing effect on the bubbles (see Marangoni effect). Surfactants actually reduce the surface tension of water by a factor of three or more. Emulsions are a type of colloidal dispersion in which surface tension plays a role. Tiny droplets of oil dispersed ...
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.
The air columns above the liquid in the two tanks are also connected by a duct. As in the free surface tanks, as the ship begins to roll the fluid flows from wing tank to wing tank causing a time varying roll moment to the ship and with careful design this roll moment is of correct phasing to reduce the roll motion of the ship.