Rod bundle flows are commonplace in nuclear engineering, and are present in&nbsp;light water reactors (LWRs) as well as&nbsp;other more advanced concepts. Inhomogeneities in the bundle cross section can lead to complex flow phenomena, including varying local conditions of turbulence. Despite the decades of numerical and experimental investigations regarding&nbsp;this topic, and the importance of elucidating the physics of the flow field, to date there are no publicly available direct numerical simulations (DNS) of the flow in multiple-pin rod bundles with heat transfer.&nbsp;In fact, there are&nbsp;only few&nbsp;data available for single-pin infinite-lattice bundles, which are of limited use in practical applications as wall effects in the cross section are always important. Thus a multiple-pin DNS study can provide significant value toward reaching&nbsp;a deeper understanding of the flow physics. Such a study would also allow for more detailed assessment and design&nbsp;of various reduced-resolution analysis techniques in the presence of heat transfer. To this end, DNS of a square 5x5 rod bundle has been performed using the highly-parallel spectral element code Nek5000. The geometrical&nbsp;dimensions were representative of typical LWR fuel designs. The DNS was designed using scales estimated from an advanced Reynolds-Averaged Navier-Stokes (RANS) model which were confirmed with LES also performed with Nek5000. The behavior of the velocity and temperature fields, as well as the Reynolds stresses,&nbsp;is presented in detail for various regions of the bundle. Finally, these results are compared and contrasted with the RANS results to identify some potential areas for further&nbsp;model development.


ICONE Competition - ICONE28-POWER2020-16643: Direct Numerical Simulation of Fluid Flow in a 5x5 Square Rod Bundle Using Nek5000

Division / Sponsors: 
Power Division & Nuclear Engineering Division (NED)

Power Conference
Paper Proceedings: https://asmedigitalcollection.asme.org/POWER/POWER2020/volume/83747

International Conference on Nuclear Engineering
Paper Proceedings: https://asmedigitalcollection.asme.org/ICONE/ICONE2020/volume/83761

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