1. n. [Enhanced Oil Recovery]

A relationship describing the pressure difference across an interface between two fluids at a static, curved interface. This relationship defines the capillary pressure difference at such an interface.

(1.) P_c = σ (1/R₁ + 1/R₂),

(2.) P_c = 2σ/r,

where
P_c = capillary pressure
σ = interfacial tension between the fluids
R₁, R₂ = principal radii of curvature of the interface
r = capillary radius.