Laminar Flow or Turbulent flow

 

SOIL WATER 

The water present in the voids of the soil mass is called soil water. 

The soil water is further classified as follow :-

(1) Free water

(2) Held water

(1)Free Water : The water which is free to move through the soil mass in called free water. It is also called gravitational  water as the movement is caused by the action of gravity only.

 (2) Held Water :- The water held in the soil pores by some forces acting in the pores of soil mass is called held water. It is in the form of structural water, capillary water or adsorbed water.

          The adsorbed water or hydroscopic water or contact moisture or surface bound moisture is that part of water which the soil particles freely adsorb from atmosphere by the physical forces of attraction. It is held by the force of adhesion.

                Capillary water is that soil  moisture which is located within the voids or capillary zone of soil . It is held due to capillary forces. Capillary action is the phenomenon of movement of water in the voids of soil due to capillary forces. The small pores of soil serve as capillary tubes through which the soil moisture rises above the ground water table. The capillary forces depends on the following:

I.        Surface tension of water

II.      Pressure of water w.r.t. atmospheric pressure.

III.    Size of capillary tubes i.e. soil pores.

Laminar Flow : The flow in which all the particles of water move in parallel paths without  crossing the path of other particles is  called a laminar flow. In such flows, the resistance to flow is  mainly due to viscosity of water only.

                Renold found a number 'N' which indicates whether the flow is laminar or turbulent. This number is known as Reynold's number and given as :

 

 

Renold number

 

For Laminar flow, N must not exceed 2000.

 Turbulent flow : The flow in which all the particles of water move in zig-zag path is called turbulent flow.