Darcy's Law

An empirical linear relation in porous media stating that the volumetric flux (specific discharge) is proportional to the applied pressure (or hydraulic head) gradient and to the medium's permeability, commonly written in continuum form as q = - (k/μ) ∇p for a Newtonian fluid under conditions where viscous forces dominate.

A continuum relation for slow, viscous flow through a porous medium stating that the volumetric flux is proportional to the pressure gradient: q = −(k/μ)∇P, where q is Darcy flux (volume per area per time), k is the medium permeability, μ the fluid viscosity and ∇P the pressure gradient. It assumes laminar pore‑scale flow and a homogenizable porous matrix.