Fluid–structure interaction with different coupled models to analyse an accident occurring in a water supply system

Fluid–structure interaction (FSI) means that neither a fluid nor a structural system can be solved independently due to the unknown forces in the interface region. The solution for such problems is based on relations of continuum mean mechanics, solved based on finite element methods, being a computational challenge due to its complex geometry, physics of fluids and the interaction between two physic means (i.e., fluid and structure). FSI simulations are mainly divided into simultaneous (direct) and partitioned (iterative) solution procedures. While in the simultaneous procedure a two-way coupled model was used, in the partitioned procedure the one-way coupled model was chosen to work with. This paper analyses an accident that occurred in a main water supply system, in Lisbon, where due to pressure variation, the pipe system suffered successive movements provoking major displacements and leading to rupture of concrete support blocks. According to the diagnosis made in situ after the accident, several analyses were developed addressing different procedures to simulate the accident and to understand the main causes behind this event.