Noncontact Detection of Water Hammer Pressure Damping in Model Pipeline with Leakage Using Digital Image Correlation and Continuous Wavelet Transform Methods

Among various diagnostic methods for leakage detection, transient test–based techniques have gained significant recognition for their ability to detect anomalies. Building upon this foundation, we propose a noncontact and nondestructive approach that integrates digital image correlation (DIC) into transient testing. DIC was employed to capture hoop strain in a 65-m-long PVC pipeline subjected to transient pressure waves generated by rapid valve closure. Laboratory experiments were conducted under four conditions: one nonleakage case and three leakage cases with leaks introduced at different upstream locations. The measured hoop strain signals were analyzed using the continuous wavelet transform. A single-degree-of-freedom model was applied using a Gabor wavelet function to estimate damping ratios from both theoretical and experimental signals. Thus, hoop strain signals under leakage conditions consistently exhibited greater damping than those under nonleakage conditions. This finding demonstrates that strain-derived damping behavior correlates with leakage presence under controlled laboratory conditions. This study examined the method under controlled laboratory conditions. These findings demonstrated the feasibility of using DIC-based noncontact strain measurement to capture damping signatures consistent with leakage in a polymeric pipe. Although field application requires further development including numerical baseline simulation, decomposition of multiple damping sources, and field validation, this study provides an experimental foundation for noncontact transient pipeline diagnostics.