PROBLEM 2

Problem 3.19. Consider the roof of a car that is moving in still, atmospheric air with a speed of 100 km/h.

The air temperature is 300 K.

a) Assuming that the car's roof is adiabatic, calculate the temperature of the roof's surface temperature at

0.25 m behind the leading edge of the roof.

b) Assume that a bug, which can be idealized as a sphere with 0.29 mm diameter, is trapped in the

boundary layer at the location described in part a so that its center is 1.13 mm away from the wall.

Estimate the drag force experienced by the bug. Also estimate the velocity difference across the bug's

body.

You can find the drag coefficient for the bug from

C₁ = [√25/Re, +0.5407],

where d is the diameter of the bug.

c) How would you find the air temperature where the bug is located? (Note that you do not need to do

calculations. You only need to explain.)