This is a follow-up to Prob. 7–37. The students measure the aerodynamic drag on their model submarine in the wind tunnel (Fig. P7–37). They are careful to run the wind tunnel at conditions that ensure similarity with the prototype submarine. Their measured drag force is 5.70 N. Estimate the drag force on the prototype submarine at the conditions given in Prob. 7–37.

Data from Problem 37

A student team is to design a human-powered submarine for a design competition. The overall length of the prototype submarine is 4.85 m, and its student designers hope that it can travel fully submerged through water at 0.440 m/s. The water is freshwater (a lake) at T = 15°C. The design team builds a one-fifth scale model to test in their university’s wind tunnel (Fig. P7–37). A shield surrounds the drag balance strut so that the aerodynamic drag of the strut itself does not influence the measured drag. The air in the wind tunnel is at 25°C and at one standard atmosphere pressure. At what air speed do they need to run the wind tunnel in order to achieve similarity?

FIGURE P7–37

Transcribed Image Text:

V Po P Wind tunnel test section Model Shield FD Drag balance - Strut