Investigation of Confluent Boundary Layers in High-Lift Flows

Abstract

The confluent boundary layers over a three-element high-lift airfoil are studied using both numerical and experimental approaches. The results suggest that wake prediction is crucial to the convergence and accuracy of the overall solution. At maximum lift, unsteadiness is observed in the experiment, which is not captured by computations. However, solutions at maximum lift indicate that, although the flow is attached over the flap, the separation bubble at the leading edge of the slat upper surface is coupled with inviscid flow reaching the compressibility limit. The thickened slat wake results in a displacement of near-surface flow over the main element and limits the main element from gaining more lift. The trends in the confluent boundary layers development require all aspects of the physics be modeled appropriately, including transition, turbulence, and inviscid-viscous interaction