Numerical simulation of two-phase flow induced vibration

In nuclear power plants, steam generator tubes vibrate because of the steam/water cross flows. In order to understand this phenomenon, reduced scale experiments are performed. Numerical simulations have shown their ability to accurately reproduce the vibration induced by a single-phase flow in a tube bundle. The aim of the present work is to do the same with two-phase flow and to characterize the effect of the physical mixture properties on vibration. To do so, a CFD code based on a two-fluid approach is used. A 'discrete forcing' method is implemented in order to allow solid body motion in a two-phase flow. The validation is performed with simple and industrial cases using experimental data and theoretical results. Using an existing implicit algorithm, a fluid-structure coupling based on the developed interface tracking method is implemented. Validated for single and two phase flows, it is now possible to have a solid motion induced by fluid forces. The different numerical models dedicated to two phase flows are then evaluated on a freon/freon flow across an inclined tube bundle. The use of a multi-regime model is required. In order to investigate the role of the different physical properties on the vibration, three simple studies are performed. Finally, the industrial application, a freon/water flow across a square pitch tube bundle, is performed. First, it is compared to a steam water flow in order to characterize the discrepancies when we are using a modeling mixture. Then, the vibration induced by single and two-phase flow is reproduced by the developed method on feasibility test cases. (author)