Jet Noise Shielding for Advanced Hybrid Wing-Body Configurations

*† We present an experimental study of jet noise shielding with an advanced design for the Hybrid WingBody airplane. The design, called N2AEXTE, features an extended trailing edge over its predecessor, the N2A. Static acoustic tests were conducted at a scale factor of 90 with realistic exhaust conditions of a bypass ratio 10 nozzle. The acoustic data show cumulative (downward +sideline) EPNL reductions of up to 10 dB with the nozzle at its nominal position and up to 13 dB with the nozzle traversed upstream by one fan diameter. These reductions are 2-3 dB better than with the basic N2A design. Redistribution of the jet noise source and incorporation of inboard vertical fins are essential elements for achieving those reductions. Devices used to alter the jet noise source comprised aggressive chevrons, a porous wedge fan flow deflector, and their combination. Two shapes for the vertical fins were tested - a nominal design and an alternate design featuring longer chord and shorter height. The alternate fin design offered slight noise benefits.