Validation of guidelines for cfd modelling of a single tube row and in-line tube bundles

This paper questions and improves commonly used guidelines for modelling a tube bundle in cross-flow at Re_D = 3.4·10⁴ and Re_D = 1.1·10⁵. Especially, when the locations of flow separation are of high interest. A major conclusion of this paper is that near-wall modelling (y⁺ < 5) is preferable and use of wall functions with y⁺ > 5 should be avoided in relation to flow separation behind tubes in cross-flow. CFD modelling of a tube bundle may be simplified with the use of symmetric or periodic boundary conditions to account for the full geometry. The present work reveals periodicity in vorticity formation between a double cylinder row, though the wake region behind a single cylinder row is neither characterised as in-phase nor reversed phase. Likewise, periodic boundary conditions may result in a modelling with large wake deflections for a full tube bundle. Furthermore, since there is no unequivocal answer to which turbulence model to apply for tubes in cross-flow, the RNG k-ε, Realizable k-ε, SST k-ω, and RSM turbulence models are tested and compared.