Modelling dump combustor flows with and without swirl at the inlet using Reynolds stress models

Numerical simulations were applied to suddenly‐expanding‐pipe flows,with and without swirl at the inlet, using an eddy‐viscosity type k‐ε model and Reynolds stress transport model variants. The predicted mean and turbulence results were compared with measurements. For the non‐swirling case, the flowfield was well represented by all the models, though the k‐ε predictions showed a slightly higher level of radial diffusive transport across the shear layer in the recirculation zone. As for the weakly swirling case, while all models, especially the stress models, give accurate values of the mean flow and turbulence fields in regions remote from the central vortex core; the biggest discrepancies between predictions and measurements occurred along the centreline in which all the models failed to reproduce correctly the strength of the decay of swirl‐induced deceleration of the axial velocity. The intensity of the turbulence along the centreline was also severely underpredicted by all the models and this contributed to the misrepresentations of the shear stresses and, hence, the mean flow development predicted by the stress models.