Aeroacoustic Analysis of Slat Tones

High-lift device noise is one of the dominant airfram noise sources. Small scale experimental studies have show characteristic tonal behavior in slat noise. In the present study experiments were carried out to assess the aeroacoustic characteristics of a 30P30N high-lift device, with particular attention to this slat tonal noise. Three different types of slat modifications, namely slat cove filler, serrated slat cusp, and slat finlets have been experimentally examined. The results are presented for an angle of attack of α = 18◦ at a free-stream velocity of U∞ = 30 m/s, which corresponds to a chord-based Reynolds number of Rec = 7 × 105. The unsteady surface pressure near the slat region and far-field noise were made simultaneously to gain a deeper understanding of the slat noise generation mechanisms. The nature of the low-frequency broadband hump and the slat tones were investigated using higher-order statistical approaches for the baseline 30P30N and modified slat configurations. Continuous wavelet transform of the unsteady surface pressure fluctuations along with secondary wavelet transform of the broadband hump and tones were carried out to analyze the intermittent events induced by the tone generating resonant mechanisms. An understanding into the nature of the noise generated from the slat will help design the new generation of quite high-lift devices.