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Surface tension is an important factor in the phenomenon of capillarity. Surface tension has the dimension of force per unit length, or of energy per unit area. [4] The two are equivalent, but when referring to energy per unit of area, it is common to use the term surface energy, which is a more general term in the sense that it applies also to ...
Even though this relationship is empirical and less precise than the surface tension of a homologous series of liquids, it is very useful considering it is a parameter of the solid surface. This method is especially used to compare and measure the critical surface tension of low-energy solids (mainly plastics) very quickly and easily.
An object or an insect can float on water due to surface tension if Bo < 1. Its inverse = =, is known as the Jesus number. [7] [10] [11] [12] Conversely, an insect can float over water if Je >1. This principle allows for animal locomotion on the surface of water.
The surface of a fluid is curved because exposed molecules on the surface have fewer neighboring interactions, resulting in a net force that contracts the surface. There exists a pressure difference either side of this curvature, and when this balances out the pressure due to gravity, one can rearrange to find the capillary length.
Water drops on a leaf A water drop falling from a tap. A drop or droplet is a small column of liquid, bounded completely or almost completely by free surfaces.A drop may form when liquid accumulates at the end of a tube or other surface boundary, producing a hanging drop called a pendant drop.
where g is the acceleration of gravity, is the viscosity of the surrounding fluid, the density of the surrounding fluid, the difference in density of the phases, and is the surface tension coefficient. For the case of a bubble with a negligible inner density the Morton number can be simplified to
Three examples of droplet detachment for different fluids: (left) water, (center) glycerol, (right) a solution of PEG in water. In fluid dynamics, the Plateau–Rayleigh instability, often just called the Rayleigh instability, explains why and how a falling stream of fluid breaks up into smaller packets with the same total volume but less surface area per droplet.
The spinning drop method is convenient compared to other widely used methods for obtaining interfacial tension, because contact angle measurement is not required. Another advantage of the spinning drop method is that it is not necessary to estimate the curvature at the interface, which entails complexities associated with shape of the fluid drop.