Control of Wake-Airfoil Interaction Noise Using Slotted-sawtooth Trailing-edge Serrations

This paper presents a study on the effectiveness of the application of a trailing-edge serration as a passive control method for reducing the wake-airfoil interaction noise from two airfoils in tandem. Two chambered airfoils, a NACA 65-(12)10 and a NACA 65-710 airfoil have been set up in tandem configuration in this study. To better understand the aerodynamic and aeroacoustic effects of wake interaction noise, an adjustment mechanism has been designed to allow free vertical movement of the rear airfoil. A slotted-sawtooth serration has been applied on the trailing-edge of the front airfoil as it has proven to be effective from our previous studies. The rear airfoil was equipped with several pressure taps and surface pressure transducers. Far-field and near-field noise have been measured using the far-field microphone array and remote sensing probe technique. The results show that the use of slotted-sawtooth serration at the angle of incidence 10 degree can lead to a significant reduction of the far-field noise as the rear airfoil starts to interact with the wake of the front airfoil. The overall noise reduction level is up to 10dB, which is believed to be due to a faster turbulence kinetic energy decay of the wake from the serrated trailing-edge. Results have also shown that a significant reduction of surface pressure fluctuation and the near-field and far-field coherence can be achieved over the leading-edge area of the rear airfoil.