A Far-field Noise and Near-field Unsteadiness of a Simplified High-lift-configuration Model (Slat)

Airframe noise generation at the flap-edge is investigated on a simplified three elements high-lift configuration wing model. Lowspeed wind tunnel experiments for aerodynamics measurements in JAXA-LWT2 and noise measurements in Large scale anechoic facility of Railway Technical Research Institute as well as steady-state Reynolds-Average NavierStokes computation (RANS) has been implemented. Cross spectrum analysis and computational results connect the far-field noise and the near-field unsteadiness, and then show the noise generation mechanism around a flap-edge. Flap-edge noise component around 2.5kHz is caused by the oscillation of the merged longitudinal vortex, which is formed by the top-side vortex and the side-edge vortex, in downstream area. The vortex is excited by shear layer instability at a lower corner of the flap-edge. In addition, three kinds of the flap-edge shape modification are tested. As a result, reduction of the far-field noise is achieved with specific shapes. Most effective modification is LowerRound flap-edge which has rounded corner at the lower side and a sharp-edge at upper side. Furthermore, variations in the vortical structures at the flap-edge with/without low noise shape are discussed using the data provided by PIV measurement and computation.

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