École Nationale Supérieure de
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Résumé

In nuclear power plants, the vibrations of steam generator tubes are induced by steam/water cross-flows. The fluid’s forces acting on these tubes can potentially lead to wear and fatigue, causing damage to the steam generator (SG) tubes. Over the past 50 years, international experimental campaigns have been undertaken to to gain a better understanding of two-phase flow induced vibrations on tube bundles. However, conducting experiments under real conditions (water at 285°C and 65 bar) remains impractical due to cost constraints, necessitating the use of simulating fluids. Consequently, the precise understanding of local-scale two-phase phenomenology within tube bundles remains relatively limited. In this context, local-scale numerical simulations emerge as valuable tools for comprehending these phenomena and investigating data that remain inaccessible through experimentation. The recent development of "multi-regime" models in the field marks a pivotal advancement, allowing the simulation of both dispersed bubbles and large-scale gas structures. This study aimed to conduct a numerical/experimental comparison across various two-phase flow regimes, utilizing the neptune_cfd calculation code. The central objective was to evaluate the neptune_cfd multi-regime model’s capacity to accurately represent two-phase cross-flows in tube bundles. Simulations were conducted for two distinct geometries: a simple pipe configuration with a cylindrical obstacle and a more complex tube bundle setup. Results derived from the neptune_cfd multi-regime model have shown a good coherence between numerical and experimental data. Notably, the model exhibited a good capacity to replicate the complex oscillatory dynamics characteristic of the slug and churn regimes. Encouragingly, these findings were achieved despite the limitations of the multi-regime model, which doesn’t take into account factors like wettability and surface tension. This aspect is particularly promising for the forthcoming thesis, which will delve into enhancing the multi-regime model of neptune_cfd by incorporating these crucial parameters.

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• Caractérisation et modélisation d'écoulements diphasiques autour d'un faisceau de tubes (deposited NON SPÉCIFIÉ)
  • Caractérisation et modélisation d'écoulements diphasiques autour d'un faisceau de tubes (deposited 30 oct. 2023 16:48) [Actuellement Affiché]