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Numerical investigation on flow mechanism in a supersonic fluidic oscillator

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Chinese Journal of Aeronautics 2021年第5期34卷 214-223页

作者： Yongjun SANG Yong SHAN Jingzhou ZHANG Xiaoming TAN Yuanwei LYU College of Energy and Power Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China

A type of supersonic fluidic oscillator is proposed and its ability to generate pulsating supersonic jet is proved in this *** two-dimensional numerical simulations reveal that the fluid transforms from subsonic to supersonic condition in the mixing chamber of oscillator after the supplied flow pressure increases from 1.1×105 Pa to 5.0×105 *** the supersonic flow is formed inside the oscillator,the wall-attached flow represents expansion wave and compression wave *** oscillating frequency will saturate to a certain value with the increase of supplied *** of the internal fluid dynamics indicates that the flow direction inside the FeedBack Channel(FBC)is related to the change of the local pressure at the inlet and the outlet of the feedback *** vortices produced in the mixing chamber present different distribution characteristics with the change of the fluid’s direction in the *** sweeping jet is divided into two jets with varying flow rate over time by the *** the end of two channels,two jets are accelerated above sound speed by convergent-divergent ***,pulsating supersonic jets are produced at two outlets for this type of fluidic oscillator.

关键词： convergent-divergent nozzle Feedback channel Flow characteristics Supersonic flow Supersonic fluidic oscillator

Effect of Boundary Layer Trip on Reduction of Jet Noise in Over-Expanded nozzle Flow

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Journal of Thermal Science 2017年第5期26卷 448-452页

作者： Masayuki ANYOJI Issei TABARU Interdisciplinary Graduate School of Engineering Sciences Kyushu University 6-1 Kasuga-koen Kasuga-city Fukuoka Japan Department of Energy and Environmental Engineering Kyushu University 6-1 Kasuga-koen Kasuga-city FukuokaJapan

A flow resonance accompanied by the emission of acoustic tones occurs in an over-expanded convergent-divergent(C-D) nozzle when operated at comparatively low pressure ratios. This phenomenon is distinguished from conventional screech tones and is referred to as "transonic tones". In contrast to screech tones, the peak resonant frequency for transonic tones increases with pressure ratio; the peak sound pressure level exceeds 110 d B. In this study, we investigated the basic characteristics of transonic resonance and tones using a circular C-D nozzle in an anechoic room. The effects of the boundary layer trip were also evaluated using a tripping wire for the suppressing transonic resonance and tones. The results of acoustic measurements show that several predominant peaks correspond to transonic tones. However, the boundary layer trip inside the nozzle effectively eliminated these tones and suppressed the unsteadiness of the flow inside the nozzle.

关键词： Transonic tones convergent-divergent nozzle noise reduction boundary layer trip

Numerical simulation on turbulent flow field in convergentdiveroent nozzle

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Journal of Coal Science & Engineering(China) 2009年第4期15卷 434-439页

作者： LU Yi-yu LIU Yongc LI Xiao-hong KANG Yong ZHAO Jian-xin College of Resources and Environmental Science Chongqing Univerisity Chongqing 400030 China

Because of the complication of turbulence＇s mechanism and law as well as the jet pressure in nozzle is difficult to test by experiment, five turbulent models were applied to numerically simulate the turbulent flow field in convergent-divergent nozzle. Theory analysis and experiment results of mass flow rates conclude that the RNG k-ε model is the most suitable model. The pressure distribution in the convergent-divergent nozzle was revealed by computational fluid dynamic （CFD） simulating on the turbulent flow field under different pressure conditions. The growing conditions of cavitation bubbles were shown; meanwhile, the phenomena in the experiment could be explained. The differential pres- sure between the upstream and downstream in nozzle throat section can improve the cavitating effect of cavitation water jet.

关键词： numerical simulation convergent-divergent nozzle turbulent flow field cavitation water jet cavitating effect

RESEARCH ON HIGH PRESSURE AIR BLOWING VALVE FOR UNDERWATER VEHICLES

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RESEARCH ON HIGH PRESSURE AIR BLOWING VALVE FOR UNDERWATER V...