Aeroacoustic simulation of transient vortex dynamics inside double-degree-of-freedom orifice-cavity structure subjected to high-intensity acoustic waves

As a noise reduction device commonly used for aero-engines at present, the double-degree-of-freedom acoustic liner has the advantage of broadband noise elimination, which is related to the energy transformation during the process of vortex generation and shedding from its dual orifice-cavity unit when subjected to high-intensity acoustic waves. Based on the compressible linear Navier-Stokes equations with the influence of nonlinear thermo-viscous acoustics, this study simulated the three-dimensional acoustic-vortex coupling field of dual orifice-cavity structures with different orifices' distances under high-intensity acoustic waves with different frequencies. The first and second resonance frequencies of the structures were found by the transmission loss coefficient. Then, through the vortex dynamics analysis, the interference behavior of the vortex shedding with fusion and shifting was observed under the first resonance frequency when the orifices' distance was close. By establishing an energy transfer model, it was found that the energy transfer was concentrated at the upper orifice under the second resonance frequency, and the interference effect increased the vortex kinetic energy and viscous dissipation energy here under the first resonance frequency. The relevant research results provide a theoretical basis for the structural optimization of aerodynamic noise control devices of modern aircraft.