###
*Hello*

###
*Flow Lines *

-are the paths which water particle follow in the course of seepage. Water flows from the point of higher head to low head.

###
*Equipotential lines *

-are the lines formed by joining the points of same head or potential on the flow lines.

###
*FLOW NETS: *

If we draw the flow lines and the equipotential lines for a given flow of water through a given soil we get a net like sketch which is known as flow net. Flow lines are always at 90 degrees to the equal potential lines.

###
**Properties of Flow net:**

- Flow lines and equal potential lines intersect each other at 90 degrees.
- The areas bounded by the flow lines and equal potential lines form approximate squares.
- Flow nets must satisfy the boundary conditions of flow field.
- Quantity of water flowing through each flow channel is the same.
- The potential drop in any two consecutive equal potential lines is same/constant.
- Flow lines and equal potential lines are smooth curves.
- Flow lines do show refraction at the interface between two soils having different coefficient of permeability.

###
**Application of Flow Net:**

**(i) Determination of seepage:**For the seepage through a flow net for isotropic condition Total Discharge, q = k.h.Nf/Nd

where, k = co-efficient of permeability

h= head causing flow

Nf= Total numbers of flow channels

Nd= Total numbers of potential drops.

**(ii) Determination of seepage pressure:**The change in the effective pressure due to flow of water is known as seepage pressure. The seepage pressure at any point can be determined by

Ps= H.Yw

where, H= hydraulic potential at any point

= h - n.h/Nd = (Nd-n).h/Nd

n = numbers of potential drops.

Thanks!

Reference: