Question

what is the renolds number

Answer 1

According to physics reynolds number is a dimensionless number used in fluid mechanics to indicate whether fluid flow past a body or in a duct is steady or turbulent.

Answer 2

Its a NUMBER calculated using the formulae :

         Inertial Force
 Re= ------------------
         Viscous Force

or

Re = σVD/μ

Re is the Reynold’s number

σ is the density of the fluid 

[I have taken sigma but u can also see the use of rho]

V is the velocity of flow of fluid

D is the diameter of the pipe

μ is the viscosity of the fluid

This number can tell us if the flow is 

1>LAMINAR

2>TURBULENT 

When the flow is less than 2000

flow is LAMINAR

WHEN the flow is MORE than 2000

the flow is TURBULENT