Numerical study of twin-jet impingement upwash flow

Two horizontally spaced jets impinging normally on a flat surface create a fountain upwash flow due to the collision of the radially flowing wall jets. This fountain flow is of importance to the dynamics and propulsion of Short Take-off and Vertical Landings (STOVL) aircraft. The fountain flow influences the lift forces on the aircraft and the ingestion of hot gases and debris by the engine inlet. A multigrid based finite difference numerical procedure has been applied to solve the equations governing this three-dimensional flow. The calculations have been performed using a reasonably fine finite difference mesh and the results have been compared with experimental data. The standard k- epsilon turbulence model has been used. Comparisons with experimental data reveal that while the mean velocities are predicted with reasonable accuracy, the turbulent kinetic energies are seriously in error. The reasons for this discrepancy could be the intense unsteadiness and large scale structures of the flow in the near wall region, which cannot be captured well by any Reynolds averaged turbulence model. (A)