### Darcy velocity field

(vector field indicating a kind of seepage in a porous medium)

A **Darcy velocity field** is a mathematical field
corresponding to fluid seepage through a porous medium,
specifically if it is following **Darcy's law**.
Darcy's law applies to non-compressible fluids
passing through a porous medium if the seepage is
sufficiently slow that inertia and turbulence
are insignificant. It describes a **Darcy velocity**,
an overall throughput rate per unit cross-section,
slower than the mean velocity of the fluid because
of the porous material through which it is passing.
It relates this to the pressure difference, gravity,
and length of the porous medium through which it
is passing.
One form:

κAΔp
Q = - ————
μL

- Q - Darcy velocity, volume per unit time.
- κ - permeability of the medium.
- A - cross-sectional area of the medium.
- Δp - difference in pressure.
- μ - viscosity of the fluid.
- L - length of the flow through the medium.

Navier-Stokes equations are more general, and Darcy's law can be
derived from them.

(*hydrology,fluid dynamics,field*)
**Further reading:**

http://en.wikipedia.org/wiki/Darcy's_law

**Referenced by pages:**

permeability (κ)

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