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Computational Thermal Sciences: An International Journal
ESCI SJR: 0.249 SNIP: 0.434 CiteScore™: 0.7

ISSN Imprimir: 1940-2503
ISSN En Línea: 1940-2554

Computational Thermal Sciences: An International Journal

DOI: 10.1615/ComputThermalScien.2016015855
pages 441-457

VALIDATION OF A MULTIFIELD APPROACH FOR THE SIMULATIONS OF TWO-PHASE FLOWS

Solène Fleau
Electricite de France, R&D Division, Chatou, France; Laboratoire de Modélisations et Simulations Multi-Echelle, Université Paris-Est Marne-la-Vallée, France.
Stephane Mimouni
Electricite de France, R&D Division, MFEE, 6 Quai Watier, 78400 Chatou, France
Nicolas Merigoux
Electricité de France, R&D Division, Chatou, France
Stephane Vincent
Laboratoire de Modélisations et Simulations Multi-Echelle, Université Paris-Est Marne-la-Vallée, France.

SINOPSIS

Safety issues in nuclear power plant involve complex bubbly flows. To predict the behavior of these flows, the two-fluid approach is often used. Nevertheless, this model induces a numerical diffusion of interfaces, which results in a poor accuracy in the calculation of the local parameters. Therefore, to simulate large interfaces such as slugs or free surfaces, interface tracking methods have been developed using the single-fluid model. In this paper, the two approaches have been coupled in the CMFD code NEPTUNE_CFD to simulate adiabatic separated flows. The averaged momentum balance equations are solved for each field and are followed by an artificial compression step, which fixes the interface thickness and ensures mass conservation. Moreover, since the two-fluid model defines a velocity per field in the whole computational domain, a drag force is used to couple the velocity of each field at the interface. This article proposes also a new formulation for this force, to take into account the physical properties of the flow. To validate this approach, an analytical test case with a static bubble has been simulated with a mesh refinement test. Then, the simulations of a rising bubble, an oscillating bubble, and the Kelvin-Helmholtz instability have been performed to highlight the effect of the modification of the drag force. Finally, model comparisons are proposed with the Kelvin-Helmholtz and the Rayleigh-Taylor instabilities.


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