In a station 3 meters downstream a flat plate, the boundary layer thickness was measured and found to be 7 cm. If this boundary layer is the result of a parallel flow of air at room temperature at a speed of 5 m/s, is the boundary layer turbulent or laminar?

Question 1

In a station 3 meters downstream a flat plate, the boundary layer thickness was measured and found to be 7 cm. If this boundary layer is the result of a parallel flow of air at room temperature at a speed of 5 m/s, is the boundary layer turbulent or laminar? what is the characteristic velocity scale and Kolmogorov length scale at this station?

Question 2

The jet engine of a commercial airplane produces 50 KN of thrust in preparation for take – off. The engine is 4 meters above the ground and has an exhaust diameter of 1 meter. What is the minimum distance for a man to stand behind the engine so that he would not encounter gusts greater than 10 m/s? (mean plus fluctuations). For simplicity, assume ambient air density at the exhaust of the engine. Also, assume the maximum fluctuating axial velocity less than three times the r.m.s velocity.