Self-sustained oscillations of the grazing flowalong the orifice of a Helmholtz resonator were considerednumerically. These fluctuations are driven by hydrodynamicinstabilities inside the shear layer and the resonant acousticalfield. Quantitative prediction of this process requires accuratecalculations of grazing flow characteristics over the threedimensional resonator. In this paper flow excitationphenomenon assumed to be associated with external pressurefluctuations within the turbulent boundary layer of grazingflow and acoustic response of the cavity. To this end a LargeEddy Simulation (LES) of the three dimensional shear flowover the orifice carried out at a low Mach number to allowpredictions of the amplitude and frequency of the pressure andvelocity fluctuations. For validation propose, for pressurefluctuations inside the cavity, a good quantitative agreementwith published data was obtained. Therefore the simulationsprovide an ability to predict the resonating frequency, pressureand velocity field for different inlet conditions.
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