Darcy's law

From Glossary of Meteorology



Darcy's law

The relationship for movement of fluids through permeable or porous media, such as soil, which states that at low Reynolds numbers the flow velocity V is proportional to hydraulic gradient dh/dl, where the constant of proportionality K is the hydraulic conductivity:
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The hydraulic head h is the height of fluid in a manometer, which is proportional to the fluid pressure, while l is the slant length in the medium along the flow streamline. The velocity V is really a specific discharge (volume flow rate of fluid per unit cross-sectional area of medium), and is sometimes called the Darcy velocity or Darcy flux. The hydraulic conductivity depends both on the permeability k of the medium (e.g., sand vs clay), and on the kinematic viscosity ν of the fluid:
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where g is gravitational acceleration.

Freeze, R. A., and J. A. Cherry 1979. Groundwater. 15–18.