Hartmann Generatorによる放射音響特性に関する基礎実験

抄録

This paper describes the experimental investigation on the radiated acoustic characteristics using the powered resonance tube called “Hartmann Generator”. The generator is constructed with the jet flow from a nozzle and a tube opened at one end (resonance tube). When the jet flow streams directly to the cavity of resonance tube, the generator has a strong acoustic resonance on the discrete frequencies. After the acoustic resonator was discovered by Hartmann in 1918, researchers have conducted extensive studies over a century. It is well known that the acoustic characteristics would change depending on the jet flow strength and the relative position between the nozzle and resonance tube. This acoustic transition is identified in 3 sort of resonant mode, i.e., Jet Instability mode (JIM), Jet Regurgitant Mode (JRG), and Jet Screech Mode (SCM). Although many researches have already done, it remains that the characteristics related to the acoustic phenomena have not been enough investigated. In this study, the authors carried out the experiments measuring the acoustic spectra in the region of the supersonic jet flow in which the resonance of JRG is excited. The acoustic radiation efficiency calculated with these experimental results shows the effect of the cavity length and the spacing between the nozzle and cavity mouth.