Abstract
Underwater pipes conveying fluids are used to transport fluids such as oil, water, and other chemicals over long distances over the sea. One of the most frequent pipeline failures is cracking. Current studies mainly rely on dynamic properties, such as natural frequencies, deflection, mode shapes, and modal damping, and curvature mode forms, to detect the beginnings of faults/cracks in cascaded pipelines. The study looks at the varying natural frequencies of a non-uniform pipe carrying a hot, viscous fluid flowing in a laminar fashion determining the depth of the fracture. The pipe in operation is subject to gravity and a constant pre-stress. The structure of the subsea pipeline has been modeled and simulated in MATLAB and subsequently, the analysis has been carried out with CFX model in ANSYS®. It has been found that the natural frequency drops as the density of the fluid that flows through the pipe increases. It is observed that natural frequency depends inversely on fracture depth irrespective of ground support. The presence of a crack in the pipeline can be ascertained, as well as its depth, by monitoring the pipe’s natural frequency. Additionally, a frequency sensitivity analysis has suggested the effects of several parameters, such as the velocity ratio, pressure head, uncertainties of the stress range, and beginning crack size have been studied in the subsea pipeline.
