Question

In model similarity, if gravitational and inertia forces are the only important forces, then what is the discharge ratio (Note: L_r is the ratio of length dimension)?
1. L_r^3/2
2.  L_r ^1/2 
3. Lr ^5/2
4. L_r^1/3

Answer 1

Correct Answer - Option 3 : Lr ^5/2

Explanation

Given, if gravitational and inertia forces are the only important forces. So it corresponds to Froude Number.

In Froude Model law,

• Scale ratio for velocity (V_r = V_m/V_p) = (L_r)0.5
• Scale ratio for time, Tr = (Lr)0.5
• Scale ratio for discharge, Qr = (Lr)2.5
• Scale ratio for Force, Fr = (Lr)3
• Scale ratio for Power, Pr = (Lr)3.5