A dual-mesh hybrid Reynolds-averaged Navier-Stokes/Large eddy simulation study of the buoyant flow between coaxial cylinders

Abdelmagid Emad Abdelmagid Ali, Imran Afgan, Dominique Laurence, Alistair Revell

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This study is concerned with the investigation of the suitability of the dual-mesh method for the buoyancy driven flow inside a cylindrical annulus with one internal cylinder. This flow situation can occur, for instance, in gas cooled nuclear reactors and is characterized by complex features, including a buoyant plume and a negatively buoyant wall-jet. The buoyancy forces in this flow are generated by the temperature difference between the inner and outer cylinders. The dual-mesh approach is a hybrid RANS-LES method in which an unsteady Reynolds-averaged Navier-Stokes (RANS) simulation and a coarse Large eddy simulation (i.e. an LES that is under-resolved near walls) are run simultaneously on two different grids. In this approach, a criterion is used to determine the locations at which each simulation is expected to perform better than the other. Consequently, at every location the less accurate simulation is forced and corrected towards the more accurate one. This correction is done using source terms that are included in the equations of the flow and thermal fields of the two simultaneous simulations. It is observed that the buoyancy-extended lengthscale resolution criterion behaves satisfactorily in defining the regions where the LES is corrected towards the RANS and vice versa. Moreover, both quantitative and qualitative analyses of the results are conducted using quasi direct numerical simulation results from the literature. It is shown that the dual-mesh method has the potential to yield results that are better than the results of the pure RANS and the pure coarse LES simulations.
Original languageEnglish
Article number111789
JournalNuclear Engineering and Design
Publication statusPublished - 1 Jul 2022


  • Hybrid RANS/LES
  • Buoyant plume
  • Negatively buoyant wall-jet
  • Cylindrical annulus
  • LES resolution
  • OpenFOAM


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