# WELL HYDRAULICS

- The velocity of flow and consequent discharge through a soil
- Depends upon various factors, such as the type of soil, the arrangement of the grains, viscosity of water etc.
- The various physical factors decide as to whether the flow will be laminar or turbulent.
- In hydraulics, the flow in pipes is generally turbulent but in soils the flow is usually laminar.
- We know that in laminar range of flow the velocity (V) of flow is proportional to hydraulic gradient (I).
- This fact was confirmed by Mr. Darcy and hence later on it was called Darcy’s law of flow.
- This law states that the rate of flow (Q) is proportional to hydraulic gradient

Q ∝ I

= KIA

\[\frac{Q}{A}= V= KI\]

**where **

- K = Darcy’s coefficient of permeability, I being dimensionless the dimension or unit of K is that of velocity (usually cm/sec.)
- V = Velocity of flow and
- A = Total cross-sectional area of soil mass perpendicular to direction of flow.
- Hence these days whole of well hydraulics is dependent upon Darcy’s law of flow through soils. This law is applicable for Laminar flows only.