Self-sustained oscillation and cavitation characteristics of a jet in a Helmholtz resonator

Self-sustained oscillations resulting from a sudden expansion in geometry, as encountered in cavities, occur in a broad array of engineering applications. In the present study, the turbulent flow past a 120°-impinging edge Helmholtz nozzle was investigated. A modified theoretical model accompanied by numerical simulation was proposed to obtain the range of the oscillation frequency and was verified using experimental results. It was found that the cavitation clouds in the chamber dominate the oscillating frequency under the low pressure-high flowrate condition. Based on the simulation results, the details of cavitation development, the motion of vortex structures, and the fluid injection and reinjection were investigated in one typical cycle. The interaction between the cavitation and the vortex formation was analyzed with the vortex transport equation. The dilatation term, which is related to the mass transfer rate through the linkage of velocity divergence, has a high value only around the bulk flow; while the baroclinic torque is predominant due to the unremitting collapse and coalescence of the cavitation clouds.