Question

Where does the Mach number finds its maximum significance?
1. Flow in closed conduit pipe
2. In cavitation studies
3. Where fluid compressibility is important
4. In capillary studies

Answer 1

Correct Answer - Option 3 : Where fluid compressibility is important

Explanation:

Number	Definition	Significance
Reynolds No	\(Re = \frac{{Inertia\;Force}}{{Viscous\;Force}} \Rightarrow \frac{{\rho VL}}{\mu }\)	Flow in closed conduit i.e. flow through pipes.
Froude No	\(Fr = \sqrt {\frac{{Inertia\;Force}}{{Gravity\;Force}}} \Rightarrow \frac{V}{{\sqrt {gL} }}\)	Where a free surface is present and gravity force is predominant. Spillway, Open Channels, waves in the ocean.
Euler No.	\({E_u} = \sqrt {\frac{{Inertia\;Force}}{{Pressure\;Force}}} \Rightarrow \frac{V}{{\sqrt {\frac{p}{\rho }} }}\)	In cavitation studies, where pressure force is predominant.
Mach No.	\(M = \sqrt {\frac{{Inertia\;Force}}{{Elastic\;Force}}} \Rightarrow \frac{V}{C}\)	Where fluid compressibility is important. Launching of rockets, airplanes and projectile moving at supersonic speed.
Weber No.	\({W_e} = \sqrt {\frac{{Inertia\;Force}}{{Surface\;tension\;Force}}} \Rightarrow \frac{V}{{\sqrt {\frac{\sigma }{{\rho L}}} }}\)	In Capillary studies i.e. where Surface tension is predominant.