Validation of Neptune_Cfd for Single-Phase Natural Convection

Abstract

Computational Fluid Dynamics (CFD) is widely used in nuclear engineering for safety related studies, providing a mechanistic solution approach in support of the system and sub-channel numerical scales applied in the safety demonstration. Co-developed by four of the biggest players of the French nuclear industry, the NEPTUNE CFD code is specialized in nuclear thermal-hydraulics applications allowing to simulate single and two-phase flows on complex geometries. The increasing protagonism of passive systems in new generation reactors demands specific studies regarding its operation and safety. Passive systems are engineered to rely on natural physical phenomena, such as buoyancy or natural convection and to operate without the need of active mechanical components or external power sources. This paper focuses on the validation of NEPTUNE CFD over experimental data of a vertical flat plane immersed in water - and semi-empiric correlations from the literature to simulate single-phase natural convection to validate the use of NEPTUNE CFD for simulating passive systems over a wide range of Rayleigh numbers from laminar to turbulent regimes.

Keywords: NEPTUNE_CFD, Natural Convection, CFD, passive systems, single-phase