Question

Water from a pipe is coming at a rate of $100$ litres per minute. If the radius of the pipe is $5cm$, the Reynolds number for the flow is of the order of : (density of water = $1000kg/m^3$, coefficient of viscosity of water = $1mPas$)

• A. $10^6$
• B. $10^3$
• C. $10^4$
• D. $10^2$

Answer 1

Answer: (C)

Reynolds Number = $\frac{\rho vd}{\eta }$
Volume flow rate = $v\times \pi r^2$
$v=\frac{100\times 10^{-3}}{60}\times \frac{1}{\pi \times 25\times 10^{-4}}$
$v=\frac{2}{3\pi }m/s$
Reynolds Number $=\frac{10^3\times 2\times 10\times 10^{-2}}{10^{-3}\times 3\pi }$
$\simeq 2\times 10^4$
order $10^4$