Darcy’s law
- Darcy’s law states that the discharge or rate of flow per unit time is proportional to hydraulic gradient
V ∝ i OR V = Ki
- Darcy’s law describes the relationship between the instantaneous rate of discharge through a porous medium and pressure drop at a distance.
Darcy’s law is expressed as:
V ∝ i OR V = Ki
i = dh/dl
Q = VA
q = Q/A = -K*(dh/dl)
Where,
q = The discharge rate
Q = The rate of water flow
K = The hydraulic conductivity
A = The column cross-section area
dh/dl = A hydraulic gradient
Limitations of Darcy’s law
- Darcy’s law is generally valid only when the flow is laminar i.e when the reynold’s number is less than on equals to 1. (Re ≤ 1)
- Darcy’s law is valid only for laminar flow, but not for turbulent flow.
- Darcy’s law is valid only for clay, silt and sand and not for gravels, cobbles etc. This is because the flow is always turbulant.
