An airplane wing is mounted in a subsonic wind tunnel with 10:1 contraction ratio.

An airplane wing is mounted in a subsonic wind tunnel with 10:1 contraction ratio. The wing is of uniform cross-section with a NACA 1412 airfoil and completely spans the test section so that the flow sees essentially an infinite wing. The wing planform area is 0.5 m2. The lift is measured with a mechanical balance that is rated for a maximum force of 5,000 N; that is, if the lift of the wing exceeds 5,000 N, the balance will be damaged. During a given test of this airfoil, the plan is to rotate the model through its entire range of angle of attack, including up to that for maximum cl.Calculate the maximum pressure difference allowable between the wind tunnel settling chamber and the test section, assuming standard sea level density in the test section (=1.23 kg/m3 and =1.8x10-5 kg/m s).