Question

A model of a golf ball is to be studied to determine the effects of the dimples. A sphere 10 times larger in diameter than an actual golf ball is used in the wind tunnel study. What speed should be selected for the model to simulate a prototype speed of 50 m/s?
1. 0.2 m/s
2. 5 m/s
3. 50 m/s
4. 10 m/s

Answer 1

Correct Answer - Option 2 : 5 m/s

Concept:

To study the effect on model and prototype, the Reynolds number of both should be the same.

\({\left( {Re} \right)_m} = {\left( {Re} \right)_p}\)

\({\left( {\frac{{\rho VD}}{\mu }} \right)_m} = {\left( {\frac{{\rho VD}}{\mu }} \right)_p}\;\)

\( \Rightarrow {\left( {V \times D} \right)_m} = {\left( {V \times D} \right)_p}\)

V × 10D = (50 × D)

⇒ V = 5 m/s