Question

What is Reynold’s number? What is its significance?

Answer 1

Turbulent flow is less likely for viscous fluid flowing at low rates. A dimensionless number, whose value gives one an approximate idea of whether the flow would be turbulent. This number is called the Reynold’s Re.
$R_e=\rho vd/\eta$
$\rho \to$ density of the fluid
speed v,d stands for the dimension of the pipe.
$\eta \to$ viscosity of the fluid. Significance is that,
flow is lamina’s/streamline for $R_e<1000$ flow is turbulent for $R_e>2000$.