Correct Answer - Option 2 : Froude Number
Explanation:
Froude Number,
\({{\rm{F}}_{\rm{r}}} = \sqrt {\frac{{{\rm{Inertia\;force}}}}{{{\rm{Gravity\;force}}}}} = {\rm{\;}}\frac{{\rm{v}}}{{\sqrt {{\rm{gL}}} }}\)
Use in open channel design i.e free surface flows
Mach Number,
\({\rm{M}} = \sqrt {\frac{{{\rm{Inertia\;force}}}}{{{\rm{Compressibility}}}}} = \frac{{\rm{V}}}{{\sqrt {\frac{{\rm{K}}}{{\rm{\rho }}}} }}\)
Use in the compressible flow
Weber Number,
\({\rm{W}} = \frac{{{\rm{Inertia\;force}}}}{{\rm{\sigma }}} = \frac{{{\rm{\rho VL}}}}{{\rm{\sigma }}}\)
Use in capillary action & surface tension
Reynold Number,
\({{\rm{R}}_{\rm{e}}} = \frac{{{\rm{Inertia\;force}}}}{{\rm{\mu }}} = \frac{{{\rm{\rho VD}}}}{{\rm{\mu }}}\)
Use in determine the flow type i.e Laminar or turbulent
Euler Number,
\({\rm{E}} = \sqrt {\frac{{{\rm{Inertia\;force}}}}{{{\rm{Pressure}}}}} = \sqrt {\frac{{\rm{V}}}{{\frac{{{\rm{\Delta P}}}}{{\rm{\rho }}}}}} \)
Use in water hammering.
∴ Model analysis for free surface flow is based on Froude’s number.
