This is a follow-up to Prob. 7–42E. The aerodynamic drag on the model in the wind tunnel (Fig. P7–42E) is measured to be 33.5 lbf when the wind tunnel is operated at the speed that ensures similarity with the prototype car. Estimate the drag force (in lbf) on the prototype car at the conditions given in Prob. 7–42E.

Data from Problem 42

The aerodynamic drag of a new sports car is to be predicted at a speed of 60.0 mi/h at an air temperature of 25°C. Automotive engineers build a one-third scale model of the car (Fig. P7–42E) to test in a wind tunnel. The temperature of the wind tunnel air is also 25°C. The drag force is measured with a drag balance, and the moving belt is used to simulate the moving ground (from the car’s frame of reference). Determine how fast the engineers should run the wind tunnel to achieve similarity between the model and the prototype.

FIGURE P7–42E

Transcribed Image Text:

Vm Wind tunnel test section Moving belt Pm² μm Lm Drag balance FD.m