Fluid-Structure Interaction in Transient-Based Extended Defect Detection of Pipe Walls

This paper investigates the effect of fluid-structure interaction (FSI) on the efficiency of transient-based reflections analysis (TBRA) applied to the detection of extended deteriorations in a reservoir-pipe-valve system. A waterhammer-with-FSI solver, based on the method of characteristics (MOC) and the finite-element method (FEM), is used and validated against available numerical and experimental results. Analytical expressions for the magnitudes of pressure reflections caused by FSI are derived. They tell how the system parameters affect FSI. The results obtained for the considered situation reveal that both pipe wall vibration (FSI) and pipe wall deteriorations may affect transient pressure in a similar, and possibly indistinguishable, way. Neglecting FSI in TBRA would skew the estimated locations, lengths, and numbers of the deteriorations in systems with considerable pipe wall axial vibration, thus making TBRA a more complicated method in flexible pipe systems.