Development of backward transient analysis in visco-elastic pressurized pipes

This paper aims to develop a backward analysis version of the inverse transient leak detection method for plastic pipes. To carry out the analysis, the structure of the Kelvin-Voigt model is modified to match the numerical structure of the backward model. Brunone unsteady friction is also discretized to make it correspond to the numerical structure. In order to investigate the performance of the improved backward transient model for pipes with visco-elastic properties, the results of this model are compared to the results of the inverse transient model applied to two cases of considering and neglecting the unsteady friction effects. The results show that in the case with a larger leak size, both models performed well. In the case with a smaller leak size, the advantage of eliminating uncertainties in the backward transient analysis (BTA) model led to the success of the model in two of three runs of leak detection; while the inverse transient analysis (ITA) in this case encountered a significant error. The unsteady friction has a negligible effect on the quality of the leak detection process in both cases. Due to the effects that the use of laboratory data with known and simple structure can have on the quality of the results, more real-life data are required to better evaluate the BTA's performance against the ITA.