Aerodynamic and aeroacoustic characteristics of propellers with different pitch

The present study investigates the effects of blade pitch on the aerodynamic loads and acoustic characteristics of propellers. Thrust and torque of propellers with different pitches are measured for a wide range of rotational speeds. Far-field acoustic pressures are measured for a wide range of rotational speeds and for different incoming flow velocities to show the effect of pitch on noise radiations at different advance ratios. Directivity and spectral analysis are performed, and results are presented to understand the distribution of acoustic radiations with frequency and emission angles, respectively. With an increase in pitch, the OASPL increases and reaches the maximum for the highest pitch setting of the propellers tested. The incoming flow significantly alters the broadband acoustic behavior of propellers. The tests are also carried out for the constant thrust conditions, and the results show that an increase in the pitch to diameter ratio leads to an increase in the sound pressure levels for the same thrust conditions for both static and dynamic thrust conditions.