Wavelet transform analysis of pressure fluctuation signals in a pressurized bubble column

Abstract

Several industrial bubble column reactors are operated at high pressures and it is important to understand its influence on the hydrodynamics and mass transfer. Pressure fluctuation signals in a pressurized bubble column are very complex since a bubble column behaves highly irregularly. The characteristics of the pressure fluctuations have been studied by several analytical methods. The recently developed technique of wavelet transform based on localized wavelet functions is applicable to the analysis of nonlinear or nonstationary pressure fluctuation signals: the time series of pressure fluctuation signals have been analyzed by means of discrete wavelet transform coefficients and multiresolution decomposition. By resorting to this wavelet transform, a pressure signal in a pressurized bubble column can be decomposed into its approximations and details at different resolutions. The energy of the details provides a measure of irregularity of the signal at various resolutions. And this wavelet transform enables us to obtain the frequency content of objects in a pressurized bubble column locally in time. In this work, the wavelet transform technique has been applied to the characterization of the fluctuating pressure signals generated in a pressurized bubble column, which are directly connected with the bubble phenomena in it. (C) 2001 Published by Elsevier Science Ltd.