GROUND WATER HYDRAULICS

GROUND WATER HYDRAULICS

Ground water hydraulics refers to movement of ground water into and out of geological formation (aquifer). Aquifer properties and fluid properties control the movement of water. The Darcy’s law is the principle of all type of ground water hydraulics

DARCY’S LAW

Law: The specific discharge (v) through the cylindrical porous media is directly proportional to head loss and inversely proportional to the length of the flow path when the flow is laminar in nature.
ig 1: Darcy’s Law experimetns





\
and


k is constant – ve sign indicate that, hydraulic gradient decreases with increase in head.



Q= - KiA
Where
i - hydraulic gradient

Darcy law is valid for ground water flow in any direction is space. In 1956 Hubert pointed out that the constant k is not a function of porous medium but also of the fluid. The new version of Darcy’s law becomes





In above equation cd2 is function of medium where rg/m is properties of fluid alone.

\ k = cd2 and K = k rg/m
Where

k - intrinsic permeability

Validity of Darcy’s Law

Darcy’s law is valid only for linear flow. The lower and upper limits of Darcy’s law are represented by Reynold’s number (Re). Darcy’s law is valid as long as Re is between 1 and 10. In most of the ground water flow conditions it is less than one.