Chapter 9, Problem 18P

A laboratory wind tunnel has a test section 25 cm square and 50 cm long. With nominal air speed U₁ = 25 m/s at the test section inlet, turbulent boundary layers form on the top, bottom, and side walls of the tunnel. The boundary-layer thickness is δ₁ = 10 mm at the inlet and δ₂ =30 mm at the outlet from the test section. The boundary-layer velocity profiles are of power-law form, with u/U = (y/δ)^1/7.     Evaluate the freestream velocity, U₂ at the exit from the wind-tunnel test section. Determine the change in static pressure along the test section.