VISCOSITY

The property of fluids by virtue of which a backward dragging force or a viscous drag acts tangentially on the layers of the fluids in motions and it tries to destroy the motion of liquid is known as viscosity .
                   

                                            
      The viscosity of liquid decreases with increase in temperature and vice versa . 
             FLOW LINE:The path of an individual particle in a moving fluid is called a flow line.
          STEADY FLOW:If the overall flow of pattern does not change with time,the flow of liquid is called steady flow.

                                  

              

                                  STREAMLINE AND TURBULENT FLOW :

The flow of liquid is said to be a streamline flow if  each particle of liquid follows exactly the same path and the same velocity as its predecessor . A streamline may be defined as a curve, the tangent to which at any point gives the direction of flow of the liquid at that point
       This holds good,however,only so long as the velocity of the liquid does not exceed a particular limiting value,called its critical velocity,beyond which the flow of the liquid loses all its steadiness and becomes zigzag,acquiring what is called a turbulent motion .