Darcy's Law

Question 1

What is a basic instrument used to measure hydraulic head in the field and in the lab?

Answer 1

Field: Piezometer
Lab: Manometer

Question 2

What is the equation for specific discharge?

Answer 2

Specific discharge (v) = Q/A
where Q = outflow in [L3/T]
and A = cross sectional area [L2]

Question 3

Describe the relations of proportionality for specific discharge with changing head and distance.

Answer 3

The specific discharge is directly proportional to h1-h2 when dl is held constant. and inversely proportional to dl when h1-h2 is held constant

Question 4

What does Darcy’s Law describe?

Answer 4

Darcy’s law describes the flow of a fluid through a porous medium.

Question 5

What is the hydraulic conductivity (K)?

Answer 5

K is a constant of proportionality. K is a function of the media and also the fluid flowing through it. K has the dimensions of velocity [L/T].
High K = porous (sand/gravel)
Low K = low porosity

Question 6

What is the relation of K, dh/dl and v?

Answer 6

If the hydraulic gradient (dh/dl) is held constant, the specific discharge (v) is proportional to hydraulic conductivity (K).

Question 7

What is the validity of Darcy’s Law assume?

Answer 7

laminar flow
saturated homogeneous isotropic media
steady state flow conditions
incompressible fluid with constant density
neglecting the kinetic energy
low Re number