Experimental study of wavy trailing edge serrations on flat rotor blades



A detailed experimental study is conducted to observe the effect of various parameters like wavelength, depth of serrations, and pitch angle on serrated blades’ acoustic emissions at low speeds up to 2000 rpm. Experiments are conducted on flat blade rotors with sinusoidal serrations on the trailing edge of blades with different amplitudes and wavelengths. A total of 7 blades with different serration configurations, including a base configuration, are studied, five of them have serrations throughout the span of the blade, and one configuration has serration of varying amplitude on the farther half of the blade. It is observed that some blade configurations have resulted in tonal noise reduction noise as much as 8dB, whereas some of the serration configurations reduce very little to none, there is no significant effect of T.E serrations on the broadband noise emitted by the rotor. Directivity of noise generated from the rotor, the effect of serrations on the directivity of the noise is studied.