Using the improved piston theory for the profile given in Problem 7.13 find the lifting pressure distribution. What can be the thickness ratio for the same profile at free stream of \(\mathrm{M}=3\) ?

Problem 7.13

What should be the minimum value of reduced frequency \(\mathrm{k}\) for a thin airfoil in a free stream Mach number of 6 so that the piston theory is valid?