Second-Moment Closure Predictions of Buoyant Jets in Neutral and Stratified Cross-Flows

Abstract

The paper considers the problem of the modelling of scalar mixing in buoyant jets discharged into neutral and stratified cross-flowing streams via a second-moment closure turbulence model. Emphasis is placed on the near-field where the 3D spatial structure is most complex. Comparisons between k - ε eddy viscosity predictions and calculations where the Reynolds stresses are modelled using the Gibson-Launder stress transport closure (but retaining an eddy diffusivity model for the scalar fluxes) indicate a noticeable improvement in comparison with measured data for the decay of peak mean density excess levels, plume spread and also the variance of density fluctuations. For the case of discharge into a linearly stratified crossflow, the current predictions show a rapid damping of the plume centreline about its equilibrium level, in agreement with measurements, but in contrast to integral models for such flows, which indicate significant oscillations.