# Blake Number

Written by Jerry Ratzlaff on . Posted in Dimensionless Numbers

Blake number, abbreviated as Bl, a dimensionless number, is proportional to inertial force and viscous force and is used in momentum transfer and flow through beds of solids.

## Blake Number formula

 $$\large{ B = \frac{ v \; \rho \; d_h }{ \mu \; \left( 1\;-\; \epsilon \right) } }$$

### Where:

 Units English Metric $$\large{ Bl }$$ = Blake number $$\large{dimensionless}$$ $$\large{ \rho }$$   (Greek symbol rho) = density of fluid $$\large{\frac{lbm}{ft^3}}$$ $$\large{\frac{kg}{m^3}}$$ $$\large{ \mu }$$  (Greek symbol mu) = dynamic viscosity of fluid $$\large{\frac{lbf-sec}{ft^2}}$$ $$\large{ Pa-s }$$ $$\large{ d_h }$$ = hydraulic diameter $$\large{ ft }$$ $$\large{ m }$$ $$\large{ v }$$ = velocity of fluid $$\large{\frac{ft}{sec}}$$ $$\large{\frac{m}{s}}$$ $$\large{ \epsilon }$$   (Greek symbol epsilon) = void fraction $$\large{dimensionless}$$

Tags: Equations for Force