Work Programme and Goals

  • Improved accuracy for the simulation of two-phase flows by validating existing models and by developing new two-phase flow models
  • Definition and coordination of experiments, necessary for the model development
  • Implementation and provision of new models and corresponding numerical methods within a special module of the CFD software ANSYS CFD
  • Reduction of user influence on the accuracy of CFD simulations by development and application of Best Practice Guidelines and checklists
  • Integration of CFD-module into the system code ATHLET
  • Because of the complexity of the flow physics and the geometries in nuclear reactors, a step-by-step approach was chosen. Initially, physical models for single-effect phenomena are developed and validated. Then combinations of flow phenomena and realistic reactor applications are considered
  • The project concept defines test cases with increasing physical complexity as follows:
  • Two-phase flows with low void fraction of the second phase
  • Two-phase flows with high void fraction of the second phase
  • Two-phase flows with free surfaces or stratification
  • Two-phase flows with phase change, for instance condensation or evaporation.

In a first step, the project partners have provided requirement specifications for these flows, describing the important physical phenomena, which need to be captured in the experiments and in the numerical simulations. These Global Software Requirement Specifications (GSRS) are the basis for the definition of a test case matrix with increasing complexity ranging from simple validation to complex industrial cases. The test cases are first simulated with existing two-phase flow models in ANSYS CFD (and other codes). The results of these calculations define the starting point for model and software improvements. They provide also information about additional experiments to obtain missing data. In addition, the CFD network develops a concept for quality assessment, ensuring a scientific validation of the software. This includes error and sensitivity analysis of experimental data and numerical results.