Parametric LES/SI Based Aeroacoustic Characterization of Tandem Orifices in Low Mach Number Flows

Abstract

Acoustic scattering and noise generation in tandem orifice configurations are examined and modelled. The modelling is carried out by a combination of Large Eddy Simulation (LES) and System Identification (SI). Hereby, an acoustically excited LES is performed. Afterwards, the acoustic data series extracted from the LES domain are post processed by means of parametric SI methods to concurrently identify both acoustic scattering and noise sources. Adopting a system theory perspective, the scattering matrix is represented by the so-called ``plant model'' whereas the noise sources are described using a ``noise model''. Here, two tandem orifice configurations are investigated to assess the influence of the distance between the two singularities on the acoustic power produced by the whole system. The acoustic power generated or dissipated across the double orifices is evaluated by means of the so-called whistling criterion. Hereby, the whistling potentiality of the two tandem orifice configurations is computed from the identified scattering matrix. The deduced acoustic power is subsequently compared against the whistling potentiality of one single orifice composing the ducted systems to evince the influence of the duct length between the singularities. Numerical results are validated against experimental data measured for the same geometries and for the same flow.