The paper examines the performance of three discretization schemes for convection and three turbulence-model variations when used to simulate the recirculating flow in an annular and a plane twin-parallel jet in still air. The discretization schemes considered are: (i) the hybrid central/upwind differencing scheme (CUDS), (ii) the hybrid central/skew-upwind differencing scheme (CSUDS) and (iii) the quadratic, upstream-weighted differencing scheme (QUDS). Of these, the second and third were proposed recently as superior alternatives to the first in respect of numerical diffusion. The turbulence models examined are the standard k-ε model and two variants of this. The first accounts for effects of streamline curvature on turbulence and the second for the preferential influence of normal stresses on the dissipation of turbulence energy. It is shown that numerical scheme (i) results, particularly in conjunction with the turbulence-model modifications, in severe solution errors and in a generally anomalous response to changes in the modelled viscosity field. In contrast, schemes (ii) and (iii) yield, in all cases, similar results and respond in an expected manner to the modifications. The modifications, particularly that accounting for streamline curvature, reduce, in some cases drastically, the discrepancies between computed and experimental data and yield for both jets examined generally satisfactory results.

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