Developments of aeroacoustic investigation on high-lift device for large aircrafts

Current method for airframe acoustic study can be categorized into prediction methodologies and experimental measurements. The experimental measurements include flight test and wind tunnel experiment. The noise prediction methodologies consist of fully analytic method, semi-empirical method, computational fluid dynamics (CFD) combining with acoustic analogy method, and fully numerical method. Over the last decades, a considerable amount of work has been conducted on noise source identification, noise mechanism, noise reduction techniques and so on. A high-lift device noise is generally categorized into three parts: low-frequency tones generated from the slat cove, mid-frequency broadband noise generated from the flap side edge, and high-frequency tones generated from the slat trailing edge. The noise reduction techniques for the high-lift device have active and passive types, including slat cove cover, slat cove filler, and continuous mold line for the passive one and blowing-suction air and plasma actuation for the active one.