Question

The velocity of the fluid relative to an immersed solid body sufficiently far from the body (outside the boundary layer) is called the free-stream velocity. With your own understanding, relate the relationships between streamline fluctuations and critical Reynold number, Rc

Answer 1

The critical reynolds number is defined as the limit where the flow regime changes from laminar flow to turbulent flow.In general,the flow is said to be laminar flow,if the calculated reynolds number is less than the Critical Reynold's number.If the calculated reynold's number is greater than the Critical Reynold's number,then the flow is said to be a turbulent flow.For flow of Newtonian Fluids in pipes,the Critical Reynold's number is set to 2100.Depending upon the type of the fluids,the Critical Reynold's number varies from 2100 to 4000.

Reynold's number is given by

N_Re=(Density*Diameter*Velocity)/(Viscosity)

The Critical Reynold's number is calculated by using the following expression:

N_Rec = (3470-1370*n)

where,n is the parameter called as power law fluid index.

The value of n varies as follows,depending on the types of flow regimes:

For Newtonian fluids, n=1, for Pseudoplastic n<1,and for Dilatant type of fluids n>1.