Question

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

• 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$
$v=\frac{100\times 10^{-3}}{60} \times \frac{1}{\pi \times25 \times 10^{-4}}$
$ v= \frac{2}{3\pi } m/s $
Reynolds Number $ = \frac{ 10^{3} \times2 \times10 \times10^{-2}}{10^{-3}\times3\pi} $
$\simeq 2 \times10^{4} $
order $10^4$