Abstract
Local fluctuations in optical transmittance and dynamic pressure signals induced by different patterns of bubble flow are examined simultaneously to extract physical information specific and common, if any, to each signal via both conventional power spectral and having recently evolved wavelet analyses. Passages of bubbles are viewed/registered at a fixed region or point in a two-dimensional (2-D) bubble column through a video camera, thin parallel laser sheet and differential pressure transducer. Apparent signal energy at each level of wavelet decomposition is utilized to determine the dominant frequency. It is found that the wavelet analysis provides more distinct values of the dominant frequencies than those evaluated from the Fourier-transform analysis in terms of power spectrum density. More importantly, the wavelet analysis is explored for further extraction of detailed information, especially time-dependent (such as shift in frequency with time) characteristics of the signals, thus providing better physical interpretation of bubbling phenomena.
