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 center dot 10(4) and ReD = 1.1 center dot 10(5). 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-E, Realizable k-epsilon, SST k-omega, and RSM turbulence models are tested and compared.