The flow net in the seepage of water through a soil medium is a network of flow lines and equipotential lines. The flow net is used to determine the seepage flow, hydro-static pressure, seepage pressure and exit gradient. A flow line or stream line in a seepage through a soil medium is defined as the path of particles of water through a saturated soil mass. The equipotential line in a seepage through a soil mass is defined as the line connecting the points of equal head of water. The direction of seepage is always perpendicular to the euipotential lines. The flow lines and equipotential line are intersecting lines at 90 degree to each other.
* The portion between any two successive flow line is known as flow channel. The potion enclosed between two successive equipotential line and successive flow line is known as field.
* The discharge (Q) passing throuh a flow net for isotropic soil is given by :
Q = KH * Nf/Nd
K = A constant
H = Total Hydraulic Head causing flow
Nf = number of flow channels
Nd = Number of potential drops