Identifying the intermittent flow sub-regimes using pressure drop time series fluctuations

From a literature survey, a deficiency has been noticed in objective methods to identify and distinct between the intermittent flow sub-regimes. Thus, the aim of this study is to analyze pressure drop fluctuations using statistical methods in order to propose simple tools to characterize the sub-regimes of the intermittent flow. The pressure drop time series were collected from experiments carried out using air–water mixture and 30 mm inner diameter pipe. The utilization of transparent pipes allowed to identify three sub-regimes which are plug flow, less aerated slug flow (LAS flow), and highly aerated slug flow (HAS flow). It was found that the probability density functions (PDF) displayed a unimodal distribution in all cases studied. Meanwhile, the representation of the base width and maximum values of PDF as functions of the gas-to-liquid superficial velocity ratio and the mixture Froude number, respectively, showed that the points for each sub-regime are clustered in the same zone. Therefore, these two feature spaces can be used to identify the sub-regimes. A third feature space, based on the statistical parameter standard deviation and kurtosis, was also proposed as a tool to distinguish between the three sub-regimes.