Measurements of natural frequency and damping constant of single steam bubble oscillating in water.
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概要
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The natural frequency <I>f<SUB>n</SUB></I> and damping constant σ of a bubble in liquid have been deter-mined by observing the resonance of the bubble to forced oscillation. The bubble was re-tained under a rigid plate horizontal disk, and the oscillation was applied by underwater speaker. The applied frequency <I>f</I> was kept constant while letting the bubble increase its volume and vary its radius R. Bubble resonance was detected by observing wrinkles appear-ing on the bubble due to surface waves. Resonance curves relating the amplitude of bubble radius variation to the intensity of applied oscillation is derived theoretically.<BR>Good agreement was seen between the data obtained from experiment and the theoreti-cally derived resonance curves at test to the validity of the method proposed of determining <I>f<SUB>n</SUB></I> and σ from bubble resonance. The values of σ and of the resonant bubble radius <I>R</I><SUB>0</SUB> of large steam bubbles (8.5 mm<<I>R</I><11.5 mm) in water were determined at <I>f</I>=270, 290 and 358Hz. The results support the assumption that for large bubbles the value of <I>f<SUB>n</SUB></I> is little influenced by the exchange of mass between liquid and gaseous phases through evaporation and condensation accompanying bubble pressure oscillation. On the other hand, σ is found to be one order of magnitude higher than calculated for steam bubbles without taking into evaporation and condensation the interphase exchange of mass. The effect brought on 5 by the interphase mass exchange can be taken into account by adding a new constant O<SUB><I>ph</I></SUB> to the terms constituting the total damping constant.
- 一般社団法人 日本原子力学会の論文