Explain and interpret the following: (a) Air pollution is often trapped within the boundary layer. (b) Clear-air turbulence (CAT) experienced by airplane passengers is widespread, but usually not very strong in the boundary layer. It tends to be more sporadic and also more intense near the tropopause. (c) Air within the free troposphere exhibits only a small diurnal temperature range. (d) Boundary layers over deserts are often much deeper than over vegetated terrain. (e) The warmest and highest-

Returning to the conditions of Problem 5.34, where the boundary layer was assumed to be fully turbulent, let us now consider the real situation where the boundary layer starts out as laminar, and then makes a transition to turbulent somewhere downstream of the leading edge. Assume a transition Reynolds number of 500,000 . For this case, calculate the percentage of drag that is due to flow separation (form drag). | Numerade

11.5: A Day in the Life of the Boundary Layer