ANALYSIS OF FLOW IN GAS-LIQUID BUBBLE-COLUMNS USING MULTIRESOLUTION METHODS

The local structure and regime transition in a gas-liquid bubble colum n are studied via multi-resolution analysis of the local gas holdup si gnal. We show that the flow in a bubble column is characterized by the energy content of the measured gas holdup signal in the time-frequenc y plane, and intermittence of the gas holdup signal, as characterized by its multifractal nature. The measured signal is decomposed into its contributions in various regions of time and frequency using wavelet- based techniques. We show that the energy distribution in time and fre quency provides greater insight into the physical processes underlying the gas-liquid flow, and may be used for on-line regime identificatio n. The intermittence of the measured signal allows characterization of the transition of the flow from the homogeneous to the heterogeneous flow regime. Both, the time-frequency distribution of energy, and the intermittence of the local gas holdup signal, are extracted via techni ques. derived from wavelet theory. Thus, wavelet analysis provides a r igorous framework for unifying statistical, spectral and fractal analy sis methods.