Aeroacoustics of High-Speed Jet Impingement

The noise from the turbulent, hot, supersonic jets at take-offs and landings dominates noise emanating from other powerplant components and has significant safety implications for launch personnel, as well as by the integrity of the structural components of the deck itself. With the impending induction of the JSF/F-35B into the US Navy in the near-future, concerns regarding noise emissions have taken added prominence. Unique to the JSF/F-35B is the requirement for it to operate in short takeoff and vertical landing mode on smaller ships, with the exhaust nozzle being vectored vertically downwards to produce lift. Jet impingement on the deck gives rise to resonant tones that are produced by a powerful acoustic feedback loop formed between the ground plane and trailing edge of the exhaust nozzle via the ambient medium. Similar noise issues also exist with regards to exhaust impingement on the jet blast deflector (JBD) on carriers. CRAFT Tech and Purdue University are implementing an innovative high-fidelity LES method for characterization of the noise sources associated with high-speed impinging jets. The farfield noise emissions are obtained with an integral technique that has been extended for jet impingement, including the effects of noise scattering from surfaces.