Question

A horizontal pipeline carrying gasoline has a cross-sectional diameter of $5mm$. If the viscocity and density of the gasoline are $6\times {10}^{-3}$ poinse and $720kg/m^3$ respectively, the velocity after which the flow becomes turbulent is

• A. $>1.66m/s$
• B. $>3.33m/s$
• C. $>1.6\times {10}^{-3}m/s$
• D. $>0.33m/s$

Answer 1

The correct option is D $>0.33m/s$

$R=\frac{\rho d}{\eta }$
$v=\frac{R\eta }{\rho d}=\frac{2\times {10}^3\times \times {15}^4}{720\times 5\times {10}^{-3}}=\frac{1}{6}\times {10}^{-5}$
$\frac{2\times {10}^3\times \times {15}^4}{720\times 5\times {10}^{-3}}=\frac{1}{300}\times 100=0.333$