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Numerical investigations of flow in nuclear fuel assembly with spacer grid and OpenFOAM validation

  • Hemish Mistry EMAIL logo
From the journal Kerntechnik


Spacer grids with mixing vanes have complex geometry and are used to support the fuel rods in nuclear fuel assemblies as well as to improve heat transfer by generating turbulence downstream of the spacer grid in the cores of the pressurized water reactors. To validate the CFD code OpenFOAM for relevant spacer grid geometries, numerical analyses on the OECD/NEA MATiS-H benchmark were performed. The flow behind two different types of spacer grid designs was analysed: split- and swirl-type. Initially, an appropriate inlet velocity profile was generated. In a next step, Computer-Aided Design models of the spacer grids were prepared and then meshed using ANSYS Mesher 19.2. Transient URANS simulations were performed with the k-ω-SST turbulence model and the results were compared with data. Good agreement was obtained for the mean velocity profile and the vorticity in the swirl-type configuration, while the numerical results slightly overestimated the transverse velocity profile at some measurements locations of the split-type configuration.[1]

Corresponding author: Hemish Mistry, Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) gGmbH, Boltzmannstrasse 14, 85748 Garching at Munich, Germany, E-mail:


The author would like to thank KAERI for providing the detailed description of the MATiS facility and the experimental data. This work was supported by the German Federal Ministry for Economic Affairs and Energy based on a decision of the German Bundestag.

  1. Author contributions: The author has accepted responsibility for the entire content of this submitted manuscript and approved submission.

  2. Research funding: The presented work is part of the project RS1591 financed by the German government.

  3. Conflict of interest statement: The author declares no conflicts of interest regarding this article.


Baglietto, E. and Ninokata, H. (2005). A turbulence model study for simulating flow inside tight lattice rod bundles. Nucl. Eng. Des. 235: 773–784, in Google Scholar

Buchholz, S., Palazzo, S., Papukchiev, A., and Scheuerer, M. (2016). Development and validation of three-dimensional CFD techniques for reactor safety applications. Final report (GRS–375). Germany.Search in Google Scholar

Cinosi, N., Walker, S.P., Bluck, M.J., and Issa, R. (2014). CFD simulation of turbulent flow in a rod bundle with spacer grids (MATIS-H) using STAR-CCM+. Nucl. Eng. Des. 279: 37–49, in Google Scholar

Dominguez-Ontiveros, E.E. and Hassan, Y.A. (2009). Non-intrusive experimental investigation of flow behavior inside a 5×5 rod bundle with spacer grids using PIV and MIR. Nucl. Eng. Des. 239: 888–898, in Google Scholar

Frank, T., Jain, S., Matyushenko, A.A., and Garbaruk, A.V. (2012). The OECD/NEA MATIS-H benchmark—CFD analysis of water flow through a 5x5 rod bundle with spacer grids using ANSYS FLUENT and ANSYS CFX. Page 12 In: Conference on experimental validation and application of CFD and CMFD codes in nuclear reactor technology, OECD/NEA and IAEA Workshop.Search in Google Scholar

Gandhir, A. and Hassan, Y. (2011). RANS modeling for flow in nuclear fuel bundle in pressurized water reactors (PWR). Nucl. Eng. Des. 241: 4404–4408, in Google Scholar

Guerrero, J. (2022). OpenFOAM advanced training. Introduction to the FVM method. Standard practices in general CFD with applications to OpenFOAM. figshare, in Google Scholar

Košmrlj, S. and Končar, B. (2012). Simulation of turbulent flow in horizontal rod bundle with split type grid spacers. In: 21st international conference nuclear energy for New Europe, September 5–7, 2012, Ljubljana, Slovenia.Search in Google Scholar

Menter, F.R. (1994). Two-equation eddy-viscosity turbulence models for engineering applications. AIAA J. 32: 1598–1605, in Google Scholar

Mikuz, B., Košmrlj, S., and Tiselj, I. (2012). OpenFOAM simulations of the turbulent flow in a rod bundle with mixing vanes in. In: 21st international conference nuclear energy for New Europe, September 5–7, 2012, Ljubljana, Slovenia.Search in Google Scholar

OECD Nuclear Energy Agency (NEA) (2015). Best practice guidelines for the use of CFD in nuclear reactor safety application – revision. OECD Publishing, Paris.Search in Google Scholar

OECD/NEA (2013). Report of the OECD/NEA-KAERI Rod Bundle CFD Benchmark Exercise, NEA/CSNI/R(2013)5 Report. OECD Publishing, Paris.Search in Google Scholar

Podila, K. and Rao, Y. (2016). CFD modelling of turbulent flows through 5×5 fuel rod bundles with spacer-grids. Ann. Nucl. Energy 97: 86–95, in Google Scholar

Smith, B.L., Song, C.H., Chang, S.K., Lee, J.R., and Kim, J.W. (2013). Report of the OECD/NEA KAERI rod bundle CFD benchmark exercise. NEA/CSNI, Paris, France, p. 5.Search in Google Scholar

Yang, S.K. and Chung, M.K. (1996). Spacer grid effects of turbulent flow in rod bundles. J. Korean Nucl. Soc. 28: 56–71.Search in Google Scholar

Received: 2022-11-21
Published Online: 2023-03-24
Published in Print: 2023-04-25

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