Institut f. Luft- u. Raumfahrt: Dissertations

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Acoustic optimization and analysis of nozzle designs with highly turbulent jets
Citation key	strasser_diss_2015_en
Author	Jean-Marie Strasser
Year	2015
DOI	10.14279/depositonce-4430
Location	Berlin
Month	April
Editor	DepositOnce - Institutional Repository for Research Data and Publications of TU Berlin
How Published	Creative Commons Namensnennung 3.0 Deutschland (CC BY 3.0 DE)
School	Technische Universität Berlin
Abstract	A numerical process chain for the acoustic design optimization of aircraft engine nozzles is presented here. This is done by using a parameterized nozzle model and a statistic acoustic cost function. Through the analysis of the influence of nozzle geometry on the emission properties of the nozzle flow, an acoustic and aerodynamic cost-benefit analysis is performed. The process chain is fully closed, and by varying the geometry function a vast number of different nozzle designs can be calculated in order to realize an acoustically optimal nozzle geometry. The parametric CAD (computer aided design) model of the nozzle is used as boundary condition of a CFD (Computational Fluid Dynamics) simulation. Then follows a rapid estimation of the the acoustic emissions from the spectrum of the resulting nozzle flow in respect to the design parameters. This is realized with the data of a steady RANS (Reynolds averaged Navier Stokes) calculation, combined with the SST (Shear Stress Transport) turbulence model and an integral CAA (Computational Aeroacoustics) method. The noise-optimized geometry parameters are finally presented in relation to the acoustic cost function for different geometry types. In the current version of the process chain, the acoustic cost function is valid for emission angle of 90° (sideline) and cold jets. The characteristics of the process chain are documented and validated here. Finally, it is shown how the process chain is applied to characterize and optimize nozzle geometries in terms of acoustic properties. Furthermore, physical aspects which cause a reduction of jet noise by adjusting the nozzle geometry, are discussed. The Nozzle design is crucial for the properties of the turbulent jet flow and jet noise. Jet noise is a key component of aircraft noise. The process chain can help to reduce jet noise if its used for predesign of noise efficient nozzles.