FRF-based transient wave analysis for the viscoelastic parameters identification and leak detection in water-filled plastic pipes

Plastic/viscoelastic pipes, such as polyvinyl chloride (PVC), polyethylene (PE) and high-density polyethylene (HDPE), have been increasingly used in water piping systems, which has stimulated the study of viscoelastic hydrodynamics in these pipe systems. An in-depth understanding of the pipe-wall viscoelasticity features is beneficial and necessary to the effective application and management of plastic pipes such as leak detection in urban water supply systems. This paper presents a frequency response function (FRF)-based transient wave analysis method (TWAM) for the identification of viscoelastic pipe properties as well as the detection of leaks in water filled plastic pipes. To this end, an analytical FRF expression is firstly derived for the interaction of transients with pipe-wall elasticity and leaks in plastic pipes, which is thereafter used for the identification of viscoelastic parameters and potential leaks in plastic pipes. Laboratory experiments are performed to validate the proposed FRF-based TWAM and thereby examining the effective range of injected wave bandwidth for accurate leak detection with existence of pipe-wall viscoelasticity. The validated method is further analyzed through extensive numerical applications to systematically examine the influences of different system and flow conditions. Application results confirm the feasibility and accuracy of the developed FRF-based TWAM method for the identification of viscoelastic parameters as well as the detection of plastic pipe leaks. The results also indicate that the proposed method in this study is more accurate to locate leaks than to size leaks in plastic pipes, which requires more attention to the future applications. (C) 2020 Elsevier Ltd. All rights reserved.