Capillary length
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In fluid mechanics, capillary length is a characteristic length scale for fluid subject to a body force from gravity and a surface force due to surface tension.
The capillary length is defined as[1]:
- ,
where g is the acceleration due to gravity and ρ is the density of the fluid, and γ is the surface tension of the fluid-fluid interface.
For clean water at standard temperature and pressure, the capillary length is ~2mm.
A capillary surface that has a characteristic length smaller than the capillary length can be considered a low Bond number surface. A sessile drop whose largest dimension is smaller than the capillary length, for example, will take the shape of spherical cap, which is the solution to the Young-Laplace equation with gravity completely absent.
[edit] See also
[edit] References
- ^ G.K. Batchelor, 'An Introduction To Fluid Dynamics', Cambridge University Press (1967)