Hilbert–Huang Spectral Analysis of Cavity Flows Incorporating Fluidic Spoilers

Abstract

Numerical aero-acoustic analysis was conducted on an M219 cavity geometry, incorporating signature suppression features and leading-edge fluidic spoilers. The numerical model was validated against existing experimental data. The palliative properties of fluidic spoilers were investigated at Mach numbers of 0.85, 1.20 and 1.80 with blowing coefficients of 0.03 and 0.06. Results are presented for the acoustic spectrum and further analysis was conducted using the Hilbert-Huang methodology. The fluidic spoilers were able to reduce considerably the overall level of acoustic noise and to reduce and/or suppress the resonant modes typical of cavity flows. The effectiveness of the spoilers was a direct consequence of their effect on the detached shear layer, of which the trajectory and coherence was altered. The Hilbert-Huang spectral analysis provided an enhanced understanding of the complex nature of the aero-acoustic behavior of the cavity. Acoustic modes were identified that, together with the Rossiter-Heller tones, govern the behavior of the spectrum. This demonstrated how the generated tones, appearing inside the cavity, were a result of complex non-linear interactions between shear layer acoustic instabilities and centrifugal instabilities originating in the flow recirculating in the internal part of the cavity. This also demonstrated that the fundamental frequencies had frequency and amplitude modu-

Influence of Door Gap on Aeroacoustics and Structural Response of a Cavity

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“…To analyse the pressure signals in the time-frequency domain, the procedure (based on the Hilbert-Huang spectral analysis [36]) already used by Bacci [32] was adopted.…”

Transoni̇k Kavi̇te Akişinin Açik Kaynakli Hesaplamali Aeroakusti̇k Anali̇zi̇

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