From the Direct Numerical Simulation to Averaged Two-Fluid Models. How different Types of Models Can Contribute to the Next Generation of Codes?

In 1998, EDF and the CEA launched the ECUME project. The aim of this project is to answer the future needs of the French nuclear industry in terms of modeling and development of two-phase thermal-hydraulic codes. Present component codes for core and steam generators such as FLICA, THYC and GENEPI and the system code CATHARE use either the 1-D two-fluid 6-equation model or 3-D models in a porous medium approach with 3-equation to 6-equation. Advanced models are being developed including transport for the volumetric interfacial area, turbulence modeling, multi-field capabilities, in a 1-D approach, and in 3-D for both porous and open media. Direct Numerical Simulation techniques are also developed to investigate some small scale local phenomena and will be used as 'numerical experiments' for solving closure problems of averaged models. For each of these new models, a state of the art and examples of first developments and applications will be presented as well as the planned future developments. (authors)