Experimental Study of Far-Field Aerodynamic Noise Characteristics of Serrated Slat

High-lift airfoil slat and passive control noise were studied experimentally. A serrated slat with different parameters was installed on the trailing edge. Far-field noise was measured in an aeroacoustic wind tunnel using a microphone array. The results showed that the generation mechanism of discrete noise in slat noise was closely related to the feedback loop in the slat cove. As the Mach number increased, the pure tone frequency moved to the right, and the peak value gradually increased, whereas the pure tone frequency was not affected by the angle of attack. Serrated slats with different sawtooth angles had different effects on the aerodynamic noise of the slat, and the frequency of discrete noise also changed. The serrated slat needed to reach a certain value in the sawtooth angle to have the effect of noise reduction. When the sawtooth angle was large, the effect of noise increase also occurred, and there was a phenomenon of mode switching. The selection of the dominant mode was also determined by the time of modal occurrence. The smaller the sawtooth angle, the more obvious the effect of slat noise. When the sawtooth angle reached a certain angle, the discrete noise disappeared, and the noise reduction effect was basically the same. The serrated slat had little effect on the lift coefficient at a low angle of attack.