A numerical study of a plane turbulent wall jet in a coflow stream

•Velocity ratio effect on the behavior of a turbulent plane wall jet is studied.•Turbulence modeling is performed by a modified low-Reynolds number k–ε model.•Numerical results are found to be in good agreement with experimental data.•Potential core length decreases with the velocity ratio.•Inertial and buoyancy forces influence the non-isothermal flow. This work is a numerical study of an isothermal and a non-isothermal turbulent plane wall jet emerging in a coflow stream with different velocity ratios ranging from 0 to 0.2. Turbulence modeling is performed by using a modified low-Reynolds number k–ε model. The numerical resolution of the governing equations was carried out via finite difference method. The present predictions are compared with those suggested in the literature. It was found that the studied model reasonably predicts the mean flow proprieties of the flow field. The main purpose of this work is to determine the influence of the velocity ratio on the dynamic, thermal and turbulent characteristics of the flow. A comparison with a simple wall jet is made. Besides, the influence of Reynolds and Richardson numbers on the wall jet emerging in a coflowing stream is examined. As far as the isothermal flow is concerned, results show that the potential core length decreases in accordance with the velocity ratio. It was also found that, downstream from the jet exit (in the established region), the longitudinal distributions of the normalized forms of the excess maximum x-velocity and the turbulent maximum kinetic energy converge to a single curve at different velocity ratios. The present investigation suggests that the effect of coflowing jet on the dynamic, thermal and turbulent parameters is negligible in the potential core area (ZFE) and the jet is similar to that of a simple jet. Further downstream of this region, the velocity ratio affects the flow as far as the high coflow streams are concerned.