Determination of bubble characteristics in bubble columns using statistical analysis of acoustic sound measurements

A systematic procedure to utilize experimental acoustic measurements in bubble columns for bubble characterization is given. Statistical tools based on zero crossings are employed to detect the bubble pulsation count and frequency. Autocorrelation functions are also exploited to provide accurate estimation of the bubble frequency. The detected bubble frequency can be used to compute the bubble size. On the other hand, the pulsation count is used to determine the bubble-size distribution. The homogeneous-heterogeneous regime transition was observed visually and confirmed by Richardson and Zaki (1954) and Ruzicka et al. (2001a) slip velocity models. Analysis of the column acoustics in the homogeneous flow regime showed a narrow bubble-size distribution, which confirms the findings from the slip velocity models. The root mean square of the acoustic pressure is used to estimate the void fraction, which revealed excellent agreement with the experimental values. The results show that acoustic hydrophones have strong potentials as 'information' sensors for on-line control of bubble columns operating at moderate conditions, and when foaming fouls classical sensors causing major control problems.