Role of length of probing waves for multi-scale defects detection in pipes

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Moez Louati, Mohamed S. Ghidaoui

Thursday 2 july 2015

14:20 - 14:35h at South America (level 0)

Themes: (T) Hydro-environment, (ST) Rehabilitation of water systems

Parallel session: 12C. Engineering - Industrial

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Partial blockages are common in engineered as well as natural pressurized conduit systems that transport liquids. Blockages in water supply systems often result in wastage of energy and financial resources, reduction in carrying capacity, increased potential for contamination. Transient-based defect detection methods (TBDDM) are highly promising because they are long range, non-intrusive, efficient and cost-effective. There are a number of past researches that focus on developing techniques and algorithm that use TBDDM to detect blockages, but there is little focus on understanding the physics of wave-blockage interaction. This paper analytically investigates the wave-blockage interaction for a single and multiple blockages with varying length scales. A harmonic wave with wavelength _ is injected into an unbounded pipe of area A containing N blockages. Each blockage is modeled as a pipe segment of length li and area Ai, where i=1,2,…N. The theoretical results are corroborated with the numerical results. As expected, _ and the intact pipe diameter are found to be the natural length scales in the longitudinal and radial direction, respectively. For blockages with small radial extent (i.e., Ai/A ~ 1), strong interaction between the injected wave and all blockages only occurs if the probing wavelength is such that the minimum li / _>>1/40. Any probing wave and blockage whose length scales do not satisfy this criteria do not interact (i.e., a wave passes through without interaction with any blockage whose length is significantly smaller than _). For blockages with Ai / A<<1, strong interaction between the injected wave and all blockages occurs provided that minimum (li / _)×(A/Ai) is of order 1.