BUBBLE COUNTING USING AN INVERSE ACOUSTIC SCATTERING METHOD

A nuclei size measurement technique is developed, based on a dispersio n relation for propagation of sound waves through a bubbly liquid. Thi s is used to relate the attenuation and phase velocity of a sound wave to the bubble population, leading to two integral equations. These eq uations are ill posed, and require special treatment for solution. Alg orithms based on a minimization method that imposes a number of physic al constraints on the solution, rendering the equation well posed, are developed. The procedure is first tested on analytical data with vary ing artificial noise added, and found to be successful in recovering t he bubble density function, and to perform much better than other publ ished solution techniques. Then, bubbles were generated using electrol ysis and air injection through porous tubes, and bubble populations me asured. Short monochromatic bursts of sound at different frequencies w ere emitted and received using hydrophones. The received signals were then processed and analyzed to obtain the attenuation and phase veloci ty. The void fraction and known experimental errors were also obtained and were fed as constraints to the inverse problem solution procedure . This resulted in bubble populations which compare favorably to those obtained by microphotography. (C) 1998 Acoustical Society of America. [S0001-4966(98)05811-1].