Numerical eduction of active multi-port data for in-duct obstructions

• Published in: Journal of sound and vibration Vol. 411; pp. 328 - 345
• Main Authors: Sack, Stefan, Shur, Michael, Åbom, Mats, Strelets, Michael, Travin, Andrey
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Ltd 22.12.2017; Elsevier Science Ltd
• Subjects: Acoustics; Aeroacoustic; Aircraft components; Channel flow; Compressible flow; Computational fluid dynamics; Computational method; Computer simulation; Detached eddy simulation; Duct acoustic; Flow simulation; IDDES; Linearity; Linearized Navier Stokes; Mathematical models; Multi-ports; Navier-Stokes equations; Network modeling; Numerical methods; Obstructions; Orifice; Power spectra; Propagation modes; Scattering; Simulation; Sound sources; Source; Turbulence; Turbulence modeling; Ventilation; Duct acoustic; Linearized Navier Stokes; IDDES; Turbulence modeling; Aeroacoustic; Multi-ports; Scattering; Orifice; Computational method; Network modeling; Source
• ISSN: 0022-460X; 1095-8568; 1095-8568
• DOI: 10.1016/j.jsv.2017.09.012

A numerical method for aeroacoustic source characterization of in-duct components at frequencies beyond the cut-on frequencies of several acoustic modes is presented. Assuming linearity and time invariance, any ducted component can be fully characterized using a network (multi-port) model including source strength and scattering. A two-step multi-source approach is applied to numerical data in order to educe the multi-port characteristics. First, a scale resolving compressible flow simulation, here the Improved Delayed Detached Eddy Simulation (IDDES), is run to compute the channel flow that also contains the acoustic sources. Second, a linear acoustic computation, here the Linearized Navier Stokes Equations (LNSE), around a mean flow is solved for different acoustic loads to determine the component's scattering. The work uncovers the high potential of two-step numerical multi-port eduction methods. Particularly, it is shown that the acoustic source power spectra can be accurately extracted from IDDES data and the total acoustic power prediction is very good. Furthermore, a good result in the scattering data obtained from a second computationally inexpensive LNSE computation is achieved. The approach is interesting when describing mid-size duct systems, for example ventilation systems in aircraft and buildings, with a moderate number of higher order modes propagating in the considered frequency range. Therefore, the increasing availability of compressible flow data opens a wide field of applications.