Acoustic resonances and trapped modes in annular plate cascades

Abstract

As a stepping stone towards understanding acoustic resonances in axial flow compressors, acoustic resonances are computed numerically in fixed single and tandem plate cascades in an infinitely long annular duct. Applying perfectly matched layer absorbing boundary conditions in the form of the complex scaling method of atomic and molecular physics to approximate the radiation condition the resonance problem is transformed into an eigenvalue problem. Of particular interest are resonances with zero radiation damping (trapped modes) or very small radiation damping (nearly trapped modes). Such resonances can be excited by wakes from compressor cascades or struts. If the shedding frequency is sufficiently close to an acoustic resonant frequency, the latter may control the vortex shedding causing high-intensity tonal noise or occasionally even blade failure. All resonances are computed for zero mean flow approximating low-Mach-number flows. The influence of various cascade parameters on the resonant frequencies is studied and, whenever possible, our numerical results are compared with published experimental findings.

Vortical–acoustic resonance in an acoustic resonator: Strouhal number variation, destabilization and stabilization

“…Similar phenomena happen in many other configurations, such as a flow duct containing plates (Parker 1966; Stoneman et al. 1988) and a compressor (Hellmich & Seume 2008), leading to an extensive study of acoustic resonance without flow in open systems (Hein, Hohage & Koch 2004; Koch 2009; Hein, Koch & Nannen 2012).…”

Frequency lock-in mechanism in flow-induced acoustic resonance of a cylinder in a flow duct

“…It causes severe noise pollution issues, as well as leading to performance deterioration or even catastrophic damage to the facility. These problems, undoubtedly, should be avoided in various military and civil engineering applications, such as combustion chambers of rockets (Karthik, Chakravarthy & Sujith 2008), compressors of aero engines (Parker 1968;Koch 2009;Liu et al 2018), front grills of automobiles (Yokoyama, Kitamiya & Iida 2013) and tube banks of heat exchangers (Mohany 2013;Shaaban & Mohany 2018). Consequently, the current research has been greatly motivated.…”