Numerical Investigation of High Frequency Wave-Leak Interaction in Water-Filled Pipes

Abstract

Actively generated pressure waves are studied widely and applied in transient-based leak detection for pipe systems. High-frequency (HF) waves, the wavelength of which is on the order of the pipe diameter or smaller, provide higher resolution to pinpoint defects. However, the mechanism of how HF waves interact with a leak is not yet well understood. This paper investigated the effect of a leak on the HF waves in a water-filled pipe using computational fluid dynamics (CFD) simulations. To facilitate the analysis, only the plane wave and the first high-order radial modes were considered. The interaction between the leak and the two modes was analyzed. The group velocity of the first high mode was analyzed to investigate the effect of the leak on the cut-off frequency. However, the shift in cut-off frequency was not observed for the moderate leak size investigated in this paper. Therefore, it was concluded that the shift of the cut-off frequency is very small and should not be used as a signature for leak detection. On the other hand, the results showed that the leak induces very significant scattering of the excited modes. Such scattering provides clear information that may be utilized for leak detection.