CFD INVESTIGATION OF A SINGLE SUBSONIC JET IN UNCONFINED CROSS-FLOW FOR ASTOVL FLOW APPLICATIONS

The behavior of turbulent jets in cross-flowing flow fields is of considerable importance to the performance of ASTOVL (Advanced Short TakeOff and Vertical Landing) aircraft. Theoretical analyses of the complicated flow field produced by jet streams in proximity to the airplane and/or the ground surface must be formulated in terms of solving the full Reynolds-Averaged Navier-Stokes (RANS) equations. This paper presents predictions of a single jet in unconfined cross-flow using the standard two-equation k-f turbulence model. The main focus is on the prediction of the static pressure coefficient on the wall from which the jet emerges. This places emphasis on the aspect of most importance in the current application, i.e., to what extent is the surface pressure field (which leads to lift) distorted by the presence of the bent-over jet. Preliminary studies were made to investigate numerical accuracy aspects of the calculations. These involved grid-refinement studies, and examination of the effect of switching from first-order (Hybrid) to second-order (Quick) convection discretization. The results presented are sensibly independent of numerical influence and represent a true assessment of the performance of the turbulence model. The CFD model performs well enough to offer designers an alternative route for estimation of jet-induced suction forces on aircraft surfaces.