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Reynolds Number Calculator

Reynolds Number estimate the ratio of intertial forces to viscous forces. Reynolds number is expressed as,
$R = \frac{\rho VD}{\mu}$

$\rho$ = density of the fluid
V = velocity of the fluid
D = diameter of the pipe
$\mu$ = viscosity of the fluid

This online Reynolds number calculator will determine Reynolds number, velocity, density, viscosity and characteristic diameter.


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Step 1: Note down the given values of parameters in the problems.

Step 2: Substitute the given values into the Reynolds number formula to get the desired unknown parameter value.
$R$ = $\frac{\rho VD}{\mu}$


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For your references, given below are some of the solved problems based on reynolds number.

Solved Examples

Question 1: A fluid of viscosity of 0.6 Ns/$m^2$ and 800 kg/$m^3$ density flows through 30 mm diameter pipe with velocity of 3.5 m/s. Determine its Reynolds number.
Step 1 : Given :
$\rho$ = 800 kg/$m^3$
$\mu$ = 0.6 Ns/$m^2$
D = 30 mm
V = 3.5 m/s
R = ?

Step 2 : Using the Reynolds number formula,
$R = \frac{\rho VD}{\mu}$

$R = \frac{800 kg/m^3 \times 3.5 m/s \times 30 \times 10^{-3}m}{0.6 Ns/m^2}$

$R = 140$

Therefore, Reynolds number is 140.

Question 2: A fluid flows at a rate of 4.5 m/s, through a pipe. The pipe is of 0.5 m diameter and the viscosity of the fluid is 1.2 Ns/$m^2$ and Reynolds number of 600. What is the density of the fluid?

Step 1: Given :
$\rho$ = ?
$\mu$ = 1.2 Ns/$m^2$
D =  0.5 m
V = 4.5 m/s
R = 600

Step 2: Using the Reynolds number formula,
R =$\frac{\rho VD}{\mu}$

$\rho$ = $\frac{R \times \mu}{V \times D}$

$\rho$ = $\frac{600 \times 1.2 Ns/m^2}{4.5 m/s \times 0.5 m}$

$\rho$ = 320 kg/$m^3$

Therefore, density of fluid is 320 kg/$m^3$.