Flow Net Construction by Graphical Method

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  1. Introduction  

The flow net can be understood as the graphical representation of the flow of water through a mass of soil.

It is curvilinear in nature and formed by the combination of the flow lines and the equipotential lines.

The main applications of the flow net in geotechnical investigations can be listed as follows:

1. Determination of the seepage discharge.

2. Determination of the seepage force.

3. Determination of the hydrostatic pressure.

4. Determination of the exit gradient.

One of the most commonly adopted methods of flow net construction is the graphical method which has been briefly explained below.


  2. Flow Net Construction by Graphical Method  

Among the various methods of flow net construction, the most convenient method is the Graphical method.

The graphical method is the method in which the flow net is constructed by an intensive trial and error procedure.

It is the simplest and the quickest method of flow net construction.

It is also the least expensive method.

Since the method includes trial and error proceedings; a lot of practice is required for achieving accurate results.

Before commencing the calculation, the available published flow nets must be studied and duly analyzed so as to get a rough idea of the nature of the flow net.

Flow Net Construction by Graphical Method


Some of the key points that must be considered while using this method are as follows:

1. The boundary conditions must be duly established.

2. It must be ensured that each flow line cut the equipotential lines at right angles to each other.

3. The space enclosed by the adjacent equipotential lines and the flow lines must be curvilinear squares.


The steps involved in the graphical method of flow net construction can be listed as follows:

1. First of all, smooth curves representing the flow lines that meet the specified requirements are first marked.

2. Then, the equipotential lines are drawn such that they cut or intersect the flow lines at right angles. It must be ensured that the equipotential lines are drawn such that the fields form approximate curvilinear squares.

3. Any defect that may be present must be identified and duly rectified.

4. The flow nets will be finally satisfactory for practical uses when the fields are curvilinear squares.

Read Also: Irrigation and Its Types  


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