Question

The aerodynamic drag of a new volvo fh truck is to be predicted at a speed of 70 km/h at an air temperature of 25oc (=1.184 /m3, =1.849×10−5/m∙). volvo engineers build a 1/3 scale model of the fh to test in a wind tunnel. the temperature of the wind tunnel is also 25oc. the drag force is measured with a drag balance, and the moving belt is used to simulate the moving ground. determine how fast the engineers should run the wind tunnel to achieve similarity between the model and the prototype?

a) 23.33 km/h
b) 70 km/h
c) 210 km/h
d) 23.33 m/s

Answer 1

The engineers should run the wind tunnel at a speed of 23.33 m/s to achieve similarity between the model and the prototype.

Step-by-step explanation:

The engineers should run the wind tunnel at a speed of 23.33 m/s to achieve similarity between the model and the prototype.

We can use the principle of geometric similarity to determine the wind tunnel speed. The scale factor for the model is 1/3, meaning that the dimensions of the model are 1/3 of the dimensions of the prototype.

The speed in the wind tunnel should be scaled by the inverse of the scale factor, so the wind tunnel speed should be 3 times the target speed of 70 km/h. This gives a wind tunnel speed of 210 km/h, or 23.33 m/s.