VARIABLE-DENSITY EFFECTS IN AXISYMMETRICAL ISOTHERMAL TURBULENT JETS - A COMPARISON BETWEEN A FIRST-ORDER AND A 2ND-ORDER TURBULENCE MODEL

The standard k-epsilon model and a second-order Reynolds stress model (RSM) are used to investigate variable density effects in axisymmetric turbulent jets. Without buoyancy, both models predict no effect of th e varying density on the far Field turbulence parameters and the class ical effective diameter concept works for the decay rates. No conclusi ve disagreement with experimental data is observed. Effects of turbule nce production due to buoyancy are found to be small compared to the e ffect of the mean buoyancy term in the momentum equation. However, thi s turbulence product:on has a large influence on the axial scalar flux , for which the experimental trend is predicted with the second-order model but not at all with the k-epsilon model. Copyright (C) 1996 Else vier Science Ltd.