Comparing CFD and 1-D solvers for the classic laminar water-hammer event in a pipe-reservoir system, perspectives on energy transformations and wave reflection

The crucially-important but well-studied water-hammer event following the rapid closure of a downstream valve is considered again here, with reference to experimental data (courtesy of Bergant et al., 1990). Three model representations are compared: (i) one-dimensional (1D) Method of Characteristics (MOC) including unsteady friction terms; (ii) 3D CFD of the pipe-only; and (iii) 3D CFD of the pipe and reservoir. The models are compared in terms of energy transformations, as well as the treatment of the wave reflection at the reservoir. Discussion includes the key limitations of the MOC, and the challenges in developing a water-hammer model in CFD.