Computation of Aeroacoustic Resonance Characteristics in Low-Speed Turbulent Flow around a Spherical Resonator

Computations of a subsonic flow over a spherical resonator placed in a straight duct are performed with the use of the hybrid scale-resolving RANS–LES approach DDES in combination with various methods for preventing the reflection of pressure disturbances from the permeable boundaries of the computational domain. It is shown that the use of a combination of characteristic boundary conditions in the inlet section of the duct with a near-boundary absorbing layer in the vicinity of its outlet section or absorbing layers in the vicinity of both permeable boundaries virtually completely eliminates false reflections from the boundaries. The results obtained with these boundary treatments are in good agreement with the experimental data both in terms of the frequency and amplitude of the aeroacoustic resonance occurring in the flow past the resonator and in the broadband part of the pressure-fluctuation spectrum inside its cavity.