Analysis of information sources in references of the Wikipedia article "Free surface" in English language version.
A simple example of irrotational flow is a whirlpool, which is known as a potential vortex in fluid mechanics.
In free-surface jets — a liquid jet in an atmosphere of air is a good approximation to a free-surface jet — the entrainment effect is usually negligible…
The term open channel flow denotes the gravity-driven flow of a liquid with a free surface.
Since, then, every molecule of a liquid is pulling on every other molecule, any body of liquid which is free to take its natural shape that is which is acted on only by its own cohesive forces, must draw itself together until it has the smallest possible surface compatible with its volume; for, since every molecule in the surface is drawn toward the interior by the attraction of the molecules within, it is clear that molecules must continually move toward the center of the mass until the whole has reached the most compact form possible. Now the geometrical figure which has the smallest area for a given volume is a sphere. We conclude, therefore, that if we could relieve a body of liquid from the action of gravity and other outside forces, it would at once take the form of a perfect sphere.
Since the molecules of liquids slide over one another readily, the force of gravity causes the surface of liquids to become level. If the force of gravity can be nullified, a small portion of free liquid will then assume a spherical form.
If a perfectly homogeneous mass of liquid be acted upon by a force which varies directly as the distance from the centre of the mass, the free surface will be of spherical form; if the mass rotates about an axis, the form assumed will be that of an oblate spheroid, which is the shape of the earth.
The free-surface vortex (whirlpool) that occurs during the draining of a basin has received different interpretations along its history;
In a partly filled tank or fish hold, the contents will shift with the movement of the boat. This "free surface" effect increases the danger of capsizing.
Surface of a body with no normal stress perpendicular or shear stresses parallel to it…
The free-surface vortex (whirlpool) that occurs during the draining of a basin has received different interpretations along its history;
