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Updated: Jun 6, 2026

High-precision Electromagnetic Flowmeter with Empty Pipe Detection via Complex Programmable Logic Device-based Waveform Recognition
Published on: June 27, 2025
Modeling and simulation of enhanced pipe detection performance via zero group velocity combined harmonics generated
Xiewen Liu1, Wujun Zhu1, Yanxun Xiang1
1Shanghai Key Laboratory of Intelligent Sensing and Detection Technology, School of Mechanical and Power Engineering, East China University of Science and Technology, Shanghai 200237, China.
None:
Pipes typically suffer from material degradation during service, necessitating reliable nondestructive inspection. Recently, zero group velocity (ZGV) combined harmonic generated by guided waves mixing was recognized as a potential mode for localized damage evaluation, but has rarely been developed. This work systematically investigates the generation mechanism and enhanced inspection performance of ZGV combined harmonics induced by counter-directional guided waves mixing in pipes, with comparative analysis against conventional combined harmonics. Theoretical analysis and modeling present that the nonlinear response of ZGV resonance is merely determined by the surface and volume power flux at the corresponding probe, endowing it exceptional sensitivity to localized degradation. Additionally, the non-propagating nature of ZGV combined harmonics eliminates cumulative effect-induced interference, overcoming a key limitation of conventional combined harmonics in degradation localization. With the optimized mode pairs and excitation conditions, numerical simulations compare the nonlinear responses and detection capabilities of ZGV and conventional combined harmonics. The nonlinear response of the ZGV combined harmonic greatly exceeds that of the conventional one, and increases more rapidly with the degradation severity or length. For both single localized degradation and two adjacent degradations, the peak positions of ZGV combined harmonic response align precisely with the degradation centers. In contrast, those of conventional combined harmonics exhibit large deviations from preset degradation centers due to cumulative effects. This study confirms that ZGV combined harmonics provide enhanced pipe inspection performance both sensitivity and localization accuracy. The findings provide an insight into advancing guided wave-based nondestructive testing techniques for localized degradation detection in pipes.
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