# Reynolds Number

In 1883, Osborne Reynold proved experimentally that in case of viscous liquid, critical velocity is given by

Vc =

Where D is diameter of tube, η coefficient of viscosity of liquid, ρ its density and N is a number, called Reynoldâ€™s number. From equations we have

N =

For a viscous liquid, flow is observed to be laminar, when N lies between 0 to 2000. The flow of liquid becomes turbulent, when the value of N is above 3000. For N between 2000 and 3000, the flow of liquid is unstable and may change from laminar to turbulent and vice-versa.

Discussion of the results
1. From the above equation it follows that for a liquid having large value of coefficient of viscosity, low value of density and flowing through a tube of narrow bore, the value of critical velocity may be too large to be possessed by the liquid. Hence, such a liquid will possess streamlined flow.
2. On the other hand, for a liquid having low value of coefficient of viscosity, large value of density and flowing through a tube of wide bore, the value of critical velocity will be very low. As this velocity can be easily attained by the liquid, the motion of such a liquid would be turbulent in nature.