Question

Value of Reynolds number for flow to be Laminar is
A. $<2000$
B. $>4000$
C. Between $2000$ and $4000$
D. Cannot be detected by Reynolds number

Answer 1

Hint: We know that fluid dynamics is a subdiscipline of fluid mechanism where we study about the flow of fluids. It is the foundation of the flow and movement of liquids and gases. As we know that there are three types of fluid flows: laminar flow, transient flow and turbulent flow.

Complete answer:
We can define Reynolds number as the ratio of inertial forces to viscous forces. It is a dimensionless term. Here inertial force can be defined as the force that allows the particles to follow the same path if any external force is not applied to the particle.

Mathematical expression of Reynolds number is given as; $R={\displaystyle \frac{\rho VD}{\mu }}$ where $V$ is the flow of velocity, $D$ = characteristic linear dimension, $\rho$ is fluid density, $\mu$ is dynamic viscosity.

Laminar flow is the flow of particles of a fluid in a straight line path or parallel to each other. In this flow layers of water flow over one another at different speeds. For laminar flow the value of Reynolds number is less than 2000 and for turbulent flow the value of Reynolds number is greater than 4000.

So, the correct answer is “Option A”.

Note:
When the viscosity increases it restricts the flow of fluid. the It is a convenient parameter for predicting if a flow condition will be laminar or turbulent. When the inertial force dominates over the viscous force that means the flow of fluid is fast, then the flow is known as turbulent.