Passive flow control of multi-element airfoils using slat mini-trailing edge device

Based on the McDonnell Douglas Aerospace three-element high lift configuration, two-dimensional unsteady Reynolds averaged Navier-Stokes equations together with shear stress transport (SST) k-ω turbulence model are employed on the multi-block structured grid of C-H type to investigate application of slat mini-trailing edge device (MTED) to passive flow control of multi-element airfoils. Considering that the actual slat slot parameters would be changed due to addition of slat MTED, effects of the slat gap, as the primary parametric variation, on the aerodynamic characteristics of the studied three-element airfoil are investigated. The results show that the maximum total lift coefficient is reduced by about 4.61% when the slat gap increases from 2.95%c to 3.98%c. The same slat MTED presents qualitatively consistent impacts on individual elements of these basic configurations with different slat gaps, namely increasing slat lift, decreasing main-element lift and almost negligible effects on flap lift. The combination of these lift changes leads to very slight change in the linear region of the total lift coefficient, but more significant variation depending on the slat gap in the stall region. When the slat gap is 3.98%c, the maximum total lift coefficient increases by about 6.98% for the configuration with the slat MTED height being 0.50%c.