Numerical simulation of grazing flow over a self-excited Helmholtz resonator

Abstract

Self-sustained oscillations of the grazing flow along the orifice of a Helmholtz resonator were considered numerically. These fluctuations are driven by hydrodynamic instabilities inside the shear layer and the resonant acoustical field. Quantitative prediction of this process requires accurate calculations of grazing flow characteristics over the three dimensional resonator. In this paper flow excitation phenomenon assumed to be associated with external pressure fluctuations within the turbulent boundary layer of grazing flow and acoustic response of the cavity. To this end a Large Eddy Simulation (LES) of the three dimensional shear flow over the orifice carried out at a low Mach number to allow predictions of the amplitude and frequency of the pressure and velocity fluctuations. For validation propose, for pressure fluctuations inside the cavity, a good quantitative agreement with published data was obtained. Therefore the simulations provide an ability to predict the resonating frequency, pressure and velocity field for different inlet conditions.