Abstract: Detachment size determination with an acoustic method has been carried out for two
interacting bubble plumes formed at neighboring needles in quiescent water. Two sets of
needle pairs, one with 1.5mm and 0.8mm inner diameters and the other with the equal 1.5mm
inner diameters, were separately used as the bubble pair injectors in the experiments.
Consequently, four typical patterns of bubble plumes interaction could be observed in the
two cases of needle pair matches. Through measuring the pressure pulses radiated by the
bubble pairs immediately after their "pinching-off " and by making use of a sophisticated
relation between oscillation frequency of volume mode and radius of gas bubble, the
detachment size of the bubble plumes have been determined from the amplitude/frequency
spectrum of the sound pressure pulses. The experimental results demonstrate that the
acoustical method is valid in both of the interacting and non-interacting circumstances in
bubble field and the bubble size measurements by this acoustical method agrees well with
the measurements from photographic analysis. Finally, a comparison has been made on the
strong and weak points of the acoustical method with the other size determination methods.

Key words: detachment size determination, sound pressure pulses, acoustical method, bubble interaction, bubble plumes

摘要： Detachment size determination with an acoustic method has been carried out for two
interacting bubble plumes formed at neighboring needles in quiescent water. Two sets of
needle pairs, one with 1.5mm and 0.8mm inner diameters and the other with the equal 1.5mm
inner diameters, were separately used as the bubble pair injectors in the experiments.
Consequently, four typical patterns of bubble plumes interaction could be observed in the
two cases of needle pair matches. Through measuring the pressure pulses radiated by the
bubble pairs immediately after their "pinching-off " and by making use of a sophisticated
relation between oscillation frequency of volume mode and radius of gas bubble, the
detachment size of the bubble plumes have been determined from the amplitude/frequency
spectrum of the sound pressure pulses. The experimental results demonstrate that the
acoustical method is valid in both of the interacting and non-interacting circumstances in
bubble field and the bubble size measurements by this acoustical method agrees well with
the measurements from photographic analysis. Finally, a comparison has been made on the
strong and weak points of the acoustical method with the other size determination methods.

关键词: detachment size determination;sound pressure pulses;acoustical method;bubble interaction;bubble plumes