Modelling the fluid structure interaction produced by a waterhammer duringshutdown of high-pressure pumps

Measurements of an experiment in a pipe system with pump shutdown and valve closing have been performed in the nuclear power plant KRB II (Gundremming en, Germany). Comparative calculations of fluid and structure including int eraction show an excellent agreement with the measured results. Theory and implementation of the fluid structure interaction (FSI) and the results of the comparison are described. The following measurements have been compared with calculations: (1) experiments in Delft, Netherlands to analyse the FS I; and (2) experiment with pump shutdown and valve closing in the nuclear p ower plant KRB II has been performed. It turns out, that the consideration of the FSI is necessary for an exact calculation of 'soft' piping systems; It has significant application in current waterhammer problems. For example , water column closure, vapour collapse, check valve slamming continues to create waterhammers in the energy industry. An important consequence of the FSI is mostly a significant increase of the effective structural damping. This mitigates-so far in all KED's calculations the FSI has taken into acco unt-an amplification of pipe movements due to pressure waves in resonance w ith structural eigenvalues. To investigate the integrity of pipe systems pi pe stresses are calculated. Taking FSI into account they are reduced by 10- 40% in the actual case. (C) 1999 Elsevier Science S.A. All rights reserved.