Designing of Slat Cove Filler as a Noise Reduction Device for Leading-edge Slat

Abstract

The purpose of this study is to design noise reduction devices for leading-edge slat which is called as a slat cove filler (SCF), from both aerodynamic and acoustic points of view. From the previous studies, a SCF seems to have an effect on reducing broadband noise by forming substantially continuous shape instead of a slat cusp configuration. However, there are some studies which indicate the decrease of aerodynamic performance when the SCF is attached. Since the primary feature of high-lift-devices is to increase aerodynamic performance, reduction of maximum lift coefficient or stall angle etc. is not acceptable even if the device is effective in reducing noise. In order understand both features, two kinds of flow solver, UPACS and UPACS-LES codes, are used to simulate steady and unsteady flows around slats. The UPACS code is used mainly for aerodynamic force prediction, and UPACS-LES is used to understand the noise generation and reduction mechanism. Based on the simulations, it became apparent that if the SCF is designed while maintaining the geometry around the slat trailing edge and the main element leading edge, the aerodynamic performance will be the same as that of the baseline. Also, to suppress the noise as much as possible, it is important to reduce small separation along the lower surface of a SCF, which seems to be caused by adverse pressure gradient. Additionally, wind tunnel experiments are performed for verification purpose. The SCF designed in this study satisfies both aerodynamic and acoustic performance successfully.