Experimental assessment of wing lower surface buffet effects induced by the installation of a UHBR nacelle

Abstract The installation of large bypass ratio engines on classical under wing configurations may lead to shock/boundary layer interaction the lower surface, limiting flight envelope in a similar way buffet occurring suction side at high incidences transonic flight. In this study, effects surface induced by Ultra-High-Bypass-Ratio through flow nacelle are assessed means wind tunnel testing. Unsteady pressure sensitive paint measurements were used assess field with temporal and spatial resolution. Strong unsteady shock motion associated separation was found for various combinations Mach number, Reynolds number angle attack. increase reducing attack present over wide range numbers. Preliminary spectral analysis suggests an upper limit frequency Strouhal about 0.4.