In a flight demonstration project for airframe noise reduction technology, FQUROH (Flight demonstration of QUiet technology to Reduce nOise from High-lift configurations), two flight demonstrations were conducted to evaluate effectiveness of noise reduction devices for main landing gear and flap side-edges using JAXA's experimental research aircraft, "Hisho". After the second flight demonstration in 2017, the validation studies of noise reduction designs have been conducted by follow-on acoustic wind tunnel tests and corresponding computational fluid dynamics (CFD) analyses. This paper presents computational studies for the flap side-edges to narrow down sources of differences among CFD, wind tunnel tests and flight test results. Influences of the geometry modifications and attachments of noise reduction devices for the flight test were investigated by CFD. The Reynolds number effects were also investigated by CFD and the importance of attention of the Reynolds number effects especially for tone noise were shown.
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