| Urban pipeline leakage has long been a fatal problem in water supply systems.There are many reasons for leaks in pipelines,such as environmental factors,human factors,and material factors.The leak detection of plastic pipelines is mainly based on acoustic detection.The related research and application of this test method only considers the single-point leakage of fluid-filled pipelines,but does not consider the timely disposal of pipelines when there is leakage in the dark.Long-term leaks can cause changes in the medium around the pipe,causing errors in the test results.Combined with the theoretical study of single leakage signal of buried water supply pipeline,this paper analyzes the vibration characteristics and experimental research of plastic pipeline when single or multiple source leakage occurs in underwater fluid-filled pipeline based on cross-correlation delay algorithm.The main contents are as follows:(1)Combining the acoustic characteristics of n=0 fluid wave,combined with the cross-correlation delay algorithm,establishes a theoretical model of single leakage signal for underwater fluid-filled pipeline.According to the characteristics of the leakage source,the theoretical model of multi-leakage signal of underwater fluid-filled pipeline is established,and the corresponding cross-power spectral density function is solved.(2)Based on the actual engineering application,the theoretical model of the leakage signal in the presence of reflected waves is established,and the influence of the reflected wave on the single and multi-source leakage signals is analyzed,and the positional relationship between the leakage source and the reflective surface is summarized.(3)Through the multi-physics coupled finite element analysis software of COMSOL Multiphysics,the two cases of single source leakage and multi-source leakage in underwater pipeline are simulated and analyzed.The stress map and phase diagram of the vibration displacement of the pipeline are obtained,and the accuracy of the theoretical model is verified.(4)Using B&K acoustic test software,the experimental platform was built to carry out the underwater pipeline leakage experiment,and the propagation characteristics of the leakage signal under water were verified by MATLAB software.Based on experimental tests,the acoustic characteristics of the leakage signal of the fluid-filled pipe are further explored under different leakage conditions(such as the size of the aperture,the size of the water pressure inside the tube,etc.).Based on the above research,it is found that the wave velocity of the leakage signal is much lower than the wave velocity of the acoustic wave in the free water,so the leakage signal cannot be radiated into the water in the underwater free field;The leakage signal is approximately non-dispersive,and its phase is approximately linear with frequency.The slope of the phase spectrum can be used to determine the delay of the leakage signal to the hydrophone.Due to the influence of the reflected wave,the slope of the phase of the frequency response function of the multi-source leakage signal is smaller than the slope of the single source leakage phase;When multiple sources leak from a pipeline,the multiple leak source can be equivalent to a new single leak source,and the location of the equivalent leak source is affected by the size of the old leak hole.The larger the size of the old leak hole,the closer the equivalent new leak source is to it.The theoretical research of this paper has played a positive role in the future research of multi-source leakage detection of pipelines.Figure [44] Table [1] Reference [66]... |
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