A very complicated three-dimensional (3D) flow field is generated beneath a Vertical/Short Take-Off and
Landing (VSTOL) aircraft when it is operated near the ground. This flow field can be represented by the configuration of
twin impinging jets along the spanwise direction in a cross-flow. This paper describes a Computational Fluid Dynamics
(CFD) study of this flow using the Reynolds Averaged Navier-Stokes (RANS) approach with a Reynolds Stress Model
(RSM). The use of an RSM potentially offers a compromise between the computational efficiency of a two equation
turbulence model and accuracy closer to that of Large Eddy Simulation (LES) although it will not be as accurate as LES.
The current numerical results are validated against experimental data and the mean velocity profiles are reasonably well
predicted by both the standard k-ε model and the RSM with slightly better prediction by the RSM. However, the Reynolds
stress prediction by the RSM is poor compared with the experimental data, indicating that to capture the detailed unsteady
flow features an LES is needed.