Abstract
Abstract
Highlights
Deep cavity oscillations are often found in many engineering applications, such as safety valves (Coffman & Bernstein 1980; Galbally et al 2015), closed side-branches in gas transport systems (Bruggeman et al 1989; Ziada 2010) and turbomachineries (Ziada, Oengören & Vogel 2002; Aleksentsev, Sazhenkov & Sukhinin 2016), as well as in riverine 917 A17-1Y.W
The common cavity oscillation involves the self-sustained oscillation that ensues from the feedback mechanism of Rossiter (1964), where Kelvin–Helmholtz disturbances are amplified in the free shear layer and the impingement of disturbances on the downstream corner produces acoustic waves, which propagate upstream to excite further instabilities in the shear layer to close the feedback loop
The present paper aims to provide an extended understanding of the feedback mechanism that reinforces the self-sustained oscillation in a deep cavity, with a particular interest in the modulation process of the shear layer oscillation and the vortex dynamics in the presence of acoustic resonance
Summary
Deep cavity oscillations are often found in many engineering applications, such as safety valves (Coffman & Bernstein 1980; Galbally et al 2015), closed side-branches in gas transport systems (Bruggeman et al 1989; Ziada 2010) and turbomachineries (Ziada, Oengören & Vogel 2002; Aleksentsev, Sazhenkov & Sukhinin 2016), as well as in riverine 917 A17-1Y.W. The presence of airflow over a deep cavity can excite a self-sustained oscillation which couples with an acoustic mode to generate intense aerodynamic noises. The acoustic reinforcement near the upstream corner amplifies the flow instabilities into coherent vortices The interaction of the latter with the downstream corner of the cavity translates into unsteady structural loadings and undesirable aerodynamic noises. Cavity oscillations that involve the interplay between the shear layer oscillation and acoustic resonance are referred to as fluid-resonant oscillations according to Rockwell & Naudascher (1978) In this oscillation regime, the flow behaviour and the speculated mechanism that enables the self-sustained oscillation differ from the conventional Rossiter’s feedback model. It is suggested that the resonant acoustic mode is the primary component that provides the upstream feedback, which strongly reinforces the shear layer oscillation (Tam & Block 1978; Tonon et al 2011; Ziada & Lafon 2014)
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