A Practical Method of Measurements System for the improving Stealth Fighter Acoustic Passive Performances (Nozzle)

So far, to this point after having optimized from a passive acoustic and vibrational point of view the performances of the nacelle and the duct of our the propulsor system (you see article precedent), we have to pass to optimize the acoustic performances of the nozzle; in fact the third contribution to the issue of the noise radiated is due to the interaction of the notable flow of exhaust gas to the nozzle opening, with the surrounding atmosphere.In this first phase is begun with numerical simulations through software ANSYS Fluent (CFD) on different typologies of nozzles (whose shape is also optimized obviously for the not electromagnetic detectability by the radars) doing well attention to avoid, in our numerical model, an alteration of the performances fluid dynamics of the same propulsor system; the author already has in mind different typologies of special nozzles on which to begin to work; in the following and experimental phase, obviously we cannot use the loudspeaker fed by a generating of signal with white noise that we had previously foreseen with no-flow (you see article precedent) since for our physical model we now have need of a not negligible gas flow to the nozzle,but we will have, to begin with a sound source type impulsive that allow us to also have a notable flow of gas that will cross our experimental nozzle (the sound source type impulsive it has the same ample acoustic spectrum in frequency as that of the signal produced by the generator of white noise);the experimental simulation, in this phase, can be effected, also with fit check explosive positions and calculated, comprised air etc. To this point it will be had to study the field of speed and turbulence to the exit of the nozzle as also that acoustic due to the interaction fluid dynamics of the gas flow with the surrounding air; the dynamic fluid experimental study will be had to effect with techniques of Laser measurement Doppler and Pulsed Laser velocimetry (it will also serve us for to provide validation of our flow model CFD computational fluid dynamics) and with measures of acoustic intensimetry for to measure the acoustic power radiated; the acoustic transfer function between two locations in the duct of our propulsor system used to determine the acoustic intensity as along the nozzle for to determine the acoustic intensity since has been established that the net acoustic power transmitted increases along the duct of the propulsor system and along the nozzle as the Mach number increases while the acoustic power radiated to the nozzle opening remains unchanged with increasing Mach number; such phenomenon of difference between transmitted power and the radiated power to the nozzle opening would seem due to the acoustic absorption caused by vorticity shedding at the nozzle opening. (for such motive they will be had to experimentally study the fields of vorticity with Optical Laser techniques Doppler and Pulsed Laser Velocimetry).

P.S.: The author accepts Job proposals with relocation (contract roles or hire roles) from countries extra EU / EU (mail to [email protected]) for a program "Stealth Fighter and Bomber" of Research and Development in circle , University, Industry, Military Defense and particularly: development and integrating advanced technology to reduce the detectability of aircraft in the electromagnetic, infrared, visual and acoustic spectrums working closely with engineers of other disciplines to optimize the integration of this technology on existing (www.at-aerospaceservice.com) and future aircraft .

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