Reynolds Number

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reynolds number 1Reynolds number, abbreviated as Re, a dimensionless number, measures the ratio of inertial forces (forces that remain at rest or in uniform motion) to viscosity forces (the resistance to flow).

 

Reynolds Number Range

Laminar flow = up to Re = 2300

Transition flow = 2300 < Re < 4000

Turbulent flow = Re > 4000

 

Reynolds number formula

\(\large{ Re = \frac{ \rho \; v \; l_c }{ \mu }  }\)
Symbol English Metric
\(\large{ Re }\) = Reynolds number \(\large{ dimensionless }\)    
\(\large{ l_c }\) = characteristic length or diameter of fluid flow  \(\large{ in }\) \(\large{ mm }\)
\(\large{ \rho }\)  (Greek symbol rho) = density of fluid \(\large{ \frac{lbm}{ft^3} }\) \(\large{ \frac{kg}{m^3} }\)
\(\large{ \mu }\)  (Greek symbol mu)  = dynamic viscosity \(\large{\frac{lbf-sec}{ft^2}}\) \(\large{ Pa-s }\)
\(\large{ v }\) = velocity of fluid \(\large{ \frac{ft}{sec} }\) \(\large{ \frac{m}{s} }\)

 

Reynolds number formula

 \(\large{ Re = \frac{ v \; l_c }{ \nu }  }\)
Symbol English Metric
\(\large{ Re }\) = Reynolds number \(\large{ dimensionless }\)    
\(\large{ l_c }\) = characteristic length or diameter of fluid flow  \(\large{ in }\) \(\large{ mm }\)
\(\large{ \nu }\)  (Greek symbol nu) = kinematic viscosity \(\large{ \frac{in^2}{sec} }\) \(\large{ \frac{mm^2}{s} }\)
\(\large{ v }\) = velocity of fluid \(\large{ \frac{ft}{sec} }\) \(\large{ \frac{m}{s} }\)

 

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Tags: Flow Equations Viscosity Equations Orifice and Nozzle Equations