Acoustic Wind Tunnel Test with 18 Scale Half-span Model toward FQUROH Second Flight Demonstration

摘要

In the FQUROH (Flight demonstration of Quiet technology to Reduce Noise from High-lift configurations) project launched by Japan Aerospace Exploration Agency (JAXA), two times of the flight demonstration using JAXA's flying test bed "Hisho" based on the Cessna Model 680 (Citation Sovereign) were carried out in 2016 and 2017. During a design process of airframe noise reduction devices, low speed wind tunnel test campaigns were conducted. This paper focuses on results of an acoustic test with 18% scale high-fidelity half-span model in RTRI-Maibara low noise wind tunnel for the FQUROH 2nd flight demonstration. At first, several shapes of the flap lower side device "PRLE" and the upper side device "VG" were compared individually, then the final combination was determined. As an assessment of the MLG devices contribution in full aircraft configuration, "wheel holes closing" and "deflector" at the leading-edge of the MLG bay which were developed in the full-scale MLG test were applied. Additional noise reduction in PNLT for the modified configuration of the 2nd demonstration predicted in the wind tunnel was l~2dB in every flyover direction. In the FQUROH 2~(nd) flight demonstration implemented in September 2017, noise reduction was successfully achieved, and two prominent benefits which were intended in the design process with CFD and the wind tunnel test were apparent. One of the benefits was disappearance of sharp peaks on the frequency spectra and the other was additional l~2dB broad band noise reduction. In a comparison of the flap noise reduction between the flight test and the 18% scale test, they had good agreement in the frequency spectra of the SPL not only at 90° flyover position but also 60°(forward) and 120°(backward) positions.