Capillary Number - Christopher Sparages: Difference between revisions

[[Image:Capillary Number.png|thumb|upright=2.6|right|Figure 1: Shows a series of different forms of the capillary number equation used in literature.^{[https://perminc.com/resources/fundamentals-of-fluid-flow-in-porous-media/chapter-2-the-porous-medium/multi-phase-saturated-rock-properties/dominance-capillary-forces-viscous-forces/capillary-number/]}]]

The capillary number (Ca) is a dimensionless number and it represents the relation between viscous forces and capillary forces, which occur between two immiscible liquids. Over the years, the capillary number has been represented by a series of different forms across literature with one of the most common one being the formalism by Saffman and Taylor (Figure 1, No. 6). <ref>[1]</ref>

The Saffman-Taylor definition for capillary number describes the ratio of (vμ)/σ with v as the fluid velocity, μ as the fluid viscosity, and σ as surface tension between the two immiscible liquids or gas and liquid. The capillary number is used to determine which forces dominate in a specific scenario. When Ca>>1, surface forces are dominated by the viscous forces. When Ca<<1, surface forces dominate the viscous forces. making the viscous forces negligible. <ref>[1]</ref>