Ask a Teacher

Assuming that the critical velocity Vc of a viscous liquid flowing through a capillary tube depends upon the radius a of the tube,the density ? and the coefficient of viscosity ? of the liquid .Obtain a relation for Vc in terms of given quantities

In a steady flow, the viscous force between the layers of a flood is F = ? A(dv/dx), where ? is the coefficient of viscosity of the liquid, A the area of the layer of the liquid and (dv/dx) the velocity gradient.

The steady or streamline flow is possible only when the liquid velocity is less than a limiting value known as critical velocity.

The flow of a liquid is steady or streamline only when the velocity of the liquid is less than the critical velocity. It was Osborne Reynold who first showed that the critical velocity Vc of a liquid flowing through a narrow is given by the relation

Vc = Re? /PD

Where Re is a constant called Reynold’s number, ? the coefficient of viscosity of the liquid (fluid), D the diameter of the tube and P the density of the liquid.