Forchheimer proposed a modification to
Darcy's Law, describing fluid flow through
packed beds in 1901. This also had a significant influence on the development of the
Ergun equation. -{dP \over dx}={\mu \over K}u+b\rho|u|u where: dP is the pressure drop across the bed, \mu is the viscosity of the fluid, K permeability (const.), u is the (area-averaged) velocity of the fluid, b is an empirical constant, \rho is the density of the fluid. A more general expression of the
friction factor follows from Forchheimers modification: f={1 \over Re}+C where Re is the
Reynolds number and C is a constant. ==Works==