The Reynolds" number is a dimensionless ratio used extensively in flow correlations and "loss" computations. Reynolds number is very important and probably most frequently used non-dimension number in fluid dynamics. To find out if the flow of gas, air, watter or any other fluid is laminar or turbulent calculation of Reynolds number (Re) is necessary.

Reynolds number is one of the most frequently used dimensionless number to find the fluid's flow regime. The Reynolds number is often regarded as the ratio of inertial forces to viscous forces - the tendency to keep moving versus the tendency to slow down.

Fluid flow can be laminar flow or turbulent flow.

Laminar flow: Re < 2000

Transitional flow: 2000 < Re < 4000

Turbulent flow: Re > 4000

Equations

Re=\frac{\rho V D}{\mu} Where:

\rho fluid density \frac{lb}{ft^3}
V fluid velocity \frac{foot}{second}
D flowing diameter ft
\mu dynamic viscosity of the fluid \frac{lb}{foot-second}

Re=92.1\frac{SG Q_1}{d \mu} Where:

SG specific gravity
Q_1 liquid flow rate BPD
d flowing diameter inches
\mu dynamic viscosity of the fluid centipoise

Re=7,738\frac{SG d V}{\mu}

Where:

SG Specific Gravity
d flowing diameter inches
V fluid velocity \frac{foot}{second}
\mu dynamic viscosity of the fluid centipoise
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