Numerical analysis of flow in the bare rod bundle of the MATIS-H test facility

In nuclear energy, continuous developments aim for safer operation and higher efficiency. Therefore determination of the distribution of thermohydraulic characteristics of the coolant flowing in fuel assemblies has been always of great importance. Lately, the usage of Computational Fluid Dynamics (CFD) codes in this field has become more and more widely spread. In this paper CFD calculations for the bare rod bundle of the MATIS-H (Measurement and Analysis of Turbulent Mixing in Subchannels-Horizontal) test facility are carried out. The effect of choice of model details is examined in order to determine the proper inlet boundary conditions needed for spacer grid calculations. First, a CFD model has been developed for a single subchannel of the test facility. This model is resolved with different meshes and effect of the mesh density on the results is studied in detail. Based on the mesh sensitivity study, a model for the full cross-section of the test bundle is developed. Using this model, effect of the turbulence model is studied. The results of the simulations are compared with data measured with Laser Doppler Anemometry (LDA).