D $=0\mathrm{.}6$ m diameter rotor with B $=16$ blades. Assume the

speed of sound to be a $=340$ m$/$s$.$

$1.$ We now place a cylindrical nacelle to test this rotor for a turbofan. Assuming that the

duct Mach number is Mx $=0\mathrm{.}5$ and using the zero of the Bessel function of J$16(18\mathrm{.}1)=0,$

what RPM does the rotor$-$locked tone become cut on$?$

$2.$ If we design the stator vane count such that the BPF due to the rotor$-$stator interaction

mode is cut$-$off until the rotor$-$locked tone is excited, what is the minimum stator vane

count which satisfies this condition?