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.