Results for a DNS of a horizontal, rectangular turbulent surface jet of aspect ratio 2:1 at a Reynolds number of 4,420 issuing into a quiescent medium are presented. The simulation is validated against experimental data. The DNS results are used to investigate sub-models used in the RANS “Basic Model” and TCL model. It is shown that the pressure-strain correlation and dissipation anisotropy models incompletely describe the near surface behaviour. These deficiencies negatively impact the prediction of the jet spreading rate and the existence of the surface layer associated with fast variations of the horizontal vorticity component
