Research on Cavitation and Noise Characteristics of Convergent-Divergent Nozzle Based on Hybrid LES/FW-H Method
In this paper,numerical simulations about the cavitation phenomena related to a convergent-divergent nozzle are performed by adopting large eddy simulation(LES)turbulence model and Rayleigh-Plesset cavitation model.The transient physical phenomena associated with the flow field are captured,and the basic characteristics concerning the cavitation noise are also obtained through the Ffowcs Williams-Hawkings(FW-H)acoustic analogy model.By regarding the pressure coefficient as a special parameter to estimate the cavitation of flow field,it is found that the cavitation inside the nozzle is caused by a combination of the shear-induced vortex structure and the Venturi effect at the nozzle throat,and the cavitation outside the nozzle is affected by a combination of the low-pressure regions due to the vortex structure and the high-pressure regions generated by the jet impinging effect.During the analysis process of cavitation noise,a decomposition method is established for the vortex and vacuole signals of a cavitation nozzle in this paper,which can successfully separate the vortex frequency components from the pressure spectrum of the cavitation flow field by monitoring and analyzing the time-domain signal of Qmax at the nozzle exit interface in the frequency domain.
CavitationLarge eddy simulationPermeable FW-H methodConvergent-divergent nozzleCavitation noise decompositionVortex shedding frequency