Suppression of junction flow effects in half model wind tunnel testing
2013-01-28T10:27:14Z (GMT) by
Half model testing is considered a valuable wind tunnel technique that offers many benefits over conventional full span testing. The technique suffers from aerodynamic losses due to flow separations on the model surfaces near the model/floor junction. Computational Fluid Dynamics, employing the Spalart-Allmaras turbulence model, and experimental investigations were carried out to evaluate the losses and to investigate the effect of localised suction on the junction flows. The wind tunnel model used was a rectangular and untwisted wing having a NASA LS(1)-0413 cross section and with a physical aspect ratio of 3. Tests were conducted at 10.00 incidence at a Reynolds number of 0.44 x 106. Aerodynamic performance of the wind tunnel half model was obtained by surface flow visualisation and pressure measurements on the wing surface in the junction region. CFD predictions showed significantly large losses compared to the experimental findings and therefore CFD predicted significant influence and benefits of suction. These were seen as elimination of the model surface separation and also recovery of the wing surface pressure distributions. In contrast to this, experiments showed much smaller separation than CFD without suction and applying suction in experiments, showed only a marginal effect on the flow separations, which also further deteriorated the pressure distributions. Future CFD studies on junction flows should be conducted using more advanced turbulence models such as Large Eddy Simulations (LES). In addition, to validate these CFD studies, velocity and turbulence measurements in the wing/floor junction region are also needed.