Recognition of onset of slug using recurrence analysis of pressure signal

Abstract

Slug is produced when the roll waves on the liquid surface undergo constructive interference and the resulting wave height increases beyond the critical height. Slug flow is associated with large aeration that develops a sudden surge in pressure and associated mechanical impact on pipe wall and bends. Such phenomena lead to flow accelerated corrosion (FAC) which results in degradation of pipe thickness with time resulting in cracks from where the gas and liquid leaks. Hence, to reduce the chances of failure in industrial pipes that are mostly opaque (flow pattern cannot be visualized) and associated hazard in nuclear power plant industries, it is important to develop mechanisms for detecting the occurrence of slug flow. The present research proposes a methodology for recognizing the onset of slug in opaque industrial pipes using the pressure signals measured from the pipeline. Recurrence analysis of pressure signal establishes different kinds of recurrence plots for stratified-wavy flow and slug flow regime. Also, the transition can be identified using the recurrence quantification parameters. The quantified parameters like recurrence rate, determinism, and entropy show sharp jump in value at the onset of slug from wavy regime.