Control of flow structure on VFE-2 delta wing with passive bleeding using CFD

Sayılır, Serdar Emin
The utilization of slender delta wings on military platforms like fighter jets and missiles has been a great topic of aerodynamics research for many decades from both experimental and numerical point of view as a result of their superior contributions to the flight performance. Second Vortex Flow Experiment (VFE-2) was carried out by NATO Research and Technology Organization between 2003 and 2008 to judge the realistic capability of the CFD codes which had been developed for simulating the leading edge vortices and their breakdowns occurring on this type of wings. In the present study, the turbulent vortical flow and its breakdown in incompressible conditions over a generic VFE-2 wing were modeled using commercial code, ANSYS Fluent. First, the grid independence study was conducted for the sharp edged 65° swept VFE-2 wing to ensure the results of the simulations do not vary with mesh density. Then, different RANS based turbulence models including Spalart-Allmaras (S-A) and SST k-ω with curvature corrections were used for validation purposes where the results of the current study were compared with both Detached Eddy Simulation (DES) results and the experimental data available in the literature. The results indicated that SST k-ω model with curvature correction was quite successful in simulating the vortical flow particularly in terms of the secondary separations and predicting the vortex breakdown location. Once a complete confidence of the grid and the turbulence model was ensured, flow control using passive bleeding was tested to check the effectiveness of bleeding on manipulating the flow field and delaying the location of vortex breakdown. The bleeding method bases on the idea of letting the air stream from the pressure side of the wing to the suction side through the holes on the wing body and injecting it into the vortical flow field to strengthen the vortex structure and delay its breakdown. For delta wings, only a limited number of applications of this passive approach yet have been implemented up until now. In the present study, the control technique was applied in three sets of investigation including variation in sizes, inclination angles and shapes of bleed holes; where in each set one parameter was altered with keeping the others constant. For each investigation set, a delay of breakdown to about 10% of the chord wise location compared to the no-control case as well as a slight improvement in the lift force and coefficient was achieved. Combining the best case parameters from each set, however, resulted a less retardation compared to the each parameter’s individual control performance.
Citation Formats
S. E. Sayılır, “Control of flow structure on VFE-2 delta wing with passive bleeding using CFD,” M.S. - Master of Science, Middle East Technical University, 2018.