A fan has a bladed rotor of 30 cm outside diameter and 12 cm inside diameter and turns at rate ω = 180 rad/s. The width of each rotor blade is 2.7 cm and the volume flow rate is Q = 0.1 m3 /s. The absolute velocity of the air (rho = 1.23 kg/m3 ) at blade inlet, V1, is purely radial. What would be a reasonable blade inlet angle (measured with respect to the tangential direction at the inside diameter of the rotor)?