Question

Value of Reynolds number for flow to be transition flow is:
A) <2000
B) >4000
C) Between 2000 and 4000
D) Cannot be decided by Reynolds number

Answer 1

Hint: The Reynolds number is used to determine whether a fluid is in laminar or turbulent flow.
Mathematically Reynolds number is defined as:
${N_{\operatorname{Re} }} = \dfrac{{\rho vd}}{\mu }$ , d is the diameter of the pipeline, $\rho $is the density of the fluid, $\mu $ is the viscosity of the fluid, v is the velocity with which fluid is flowing.

Complete step by step solution:
Let us discuss the Reynolds number in details:
Reynolds numbers help predict flow patterns in different fluid flow situations. At low Reynolds number, flows tend to be dominated by laminar flow, while at high Reynolds number flow of the fluid tends to be turbulent.
The turbulence of the fluid results from the differences in the velocity of the fluid which may sometimes intersect or move counter to the overall direction of the flow. Reynolds numbers are an important dimensionless quantity of the fluid mechanics.
Now we will discuss the options given in the question.
Flow with Reynolds number less than 2000 is considered as the Laminar flow but in the question we have to answer about transition flow.
Reynolds numbers which are greater than 4000 have the turbulent flow.
Therefore, the transition flow will be between 2000 and 4000.

Option, (C) is correct.

Note: Reynolds number plays an important part in the calculation of the friction factor, It is used when modeling the movement of organisms swimming through water. Atmospheric air is also considered to be a fluid, hence its Reynolds number is also calculated, It plays an important part in the testing of wind lift on aircraft.