Numerical investigation of high-frequency wave-leak interaction in water-filled pipes

摘要

Actively generated pressure waves are widely studied and applied in transient-based leak detection for pipe systems. High-frequency waves (HFW), where the wavelength is of the order of pipe diameter or smaller, provide the required resolution to pinpoint defects. However, the mechanism of how HFW interact with a leak is not yet well understood. This paper investigates the effect of a leak on the HFW 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 are considered. The interaction between the leak and the two modes are analyzed. The group velocity of the first high mode is measured to verify the cut-off frequency shift. However, such shift could not be observed and therefore it is concluded to be very small if at all. The results show that the leak tilts the plane wave and reduces the amplitude of both the plane wave and the first high mode wave. Moreover, mode scattering occurs at the leak and might be used as an indication of defect signature.