Predictions of the Acoustic Nearfield on a Carrier Deck Navy SBIR FY2010.2 Sol No.: Navy SBIR FY2010.2 Topic No.: N102-128 Topic Title: Predictions of the Acoustic Nearfield on a Carrier Deck Proposal No.: N102-128-0538 Firm: Hersh Acoustical Engineering, Inc. 22305 Cairnloch Street Calabasas, California 91305-5875 Contact: Alan Hersh Phone: (818) 224-4699 Abstract: On a carrier deck, navy personnel operate in close proximity to high-speed jets. They are, therefore, exposed to high intensity jet noise resulting in possible severe loss of hearing. The objective of the project is to develop jet noise prediction capability for quantitative assessment of the acoustic environment on an active carrier deck. Such assessment would allow the identification of noise hot spots to be avoided. Jet noise consists of three principal components; the fine-scale turbulence noise, the large turbulence structures noise and the broadband shock-cell noise. For military jets, the large structures noise is most intense and dominant. It is the focus of this project. Specifically, the aim is to develop a physics-based prediction method. It is known that large turbulence structures are spatially and temporally coherent. The noise is highly direction. The mechanism is Mach wave radiation. All these important characteristics will be incorporated into the model prediction theory. The theory will follow the highly successful Tam and Auriault (1999) fine-scale turbulence noise theory with the characteristics of fine scale turbulence replaced by those of the large turbulence structures. The Green's function method will be used to propagate noise from source to the near and far field. Benefits: Results of Phase I work will make it possible for Navy to have a reliable prediction method for the noise of military (single stream supersonic) jets. Currently, available jet noise prediction methods such as the SAE method, the NASA ANOPP codes and various company proprietary methods are largely empirical. The method to be developed will take into account all essential physics of jet aeroacoustics. That is, it is physics-based. Commercial jet engines are quite different from military engines. They are designed for efficiency and not for thrust alone. In spite of the basic differences, however, successful development of an accurate, reliable jet noise prediction method for single stream jets would be a good starting point for extension to dual stream jets for commercial jet engine application. Return