An application of the wavelet analysis technique for the objective discrimination of two-phase flow patterns

This paper presents an application of the wavelet analysis technique for two-phase flow pattern identification by using the void fraction signals obtained from a multi-channel Impedance Void Meter (IVM) in a vertical-upward air–water flow. A new method for the objective discrimination of the two-phase flow pattern has been developed to provide information regarding the local energy of void fraction signals at a given scale on the joint time–frequency diagram. The void signals are processed with Continuous Wavelet Transform (CWT) to get the local wavelet energy coefficients map on the time–frequency diagram. The effective local wavelet energy and the effective scale are then calculated. Then the criteria for flow pattern identification are, finally, obtained. A series of void fraction measurements were conducted over a wide range of air–water vertical-upward flow condition to provide an extensive database to cover several types of flow patterns. The results show that the proposed method has a high precision for characterizing different flow regimes in two-phase flow, and is considerably more promising for the online recognition of two-phase flow patterns due to the short time of data processing.