Question

Water flows at a speed of 6 cm s⁻¹ through a tube of radius 1 cm. Coefficient of viscosity of water at room temperature is 0.01 poise. Calculate the Reynolds number. Is it a steady flow?

Answer 1

Given:
Speed of water, v = 6 cm/s = 6 × 10⁻² m/s
Radius of tube, r = 1 cm = 10⁻² m
Diameter of tube, D = 2 × 10⁻² m
Coefficient of viscosity, η = 0.01 poise

Let the Reynolds number be R and the density of water be ρ.

$$\begin{gathered} \Rightarrow R=\frac{vpD}{\eta } \\ =\left(6\times {10}^{-3}\right)\times {10}^3\times \frac{2\times {10}^{-2}}{{10}^{-2}} \\ =120 \end{gathered}$$

Here, the Reynolds number is less than 2000. Therefore, it is a steady flow.