Aerodynamic Performance of Different Trailing-edge Serrations for High Reynolds Number Flows around Wing-flap System

In the present work different trailing-edge serration models are designed and their aerodynamic performances at realistic landing conditions around a wing-flap system are investigated. The serration model with the best performance is then introduced. The NLR 7301 wing and single-slotted flap is selected as reference geometry and three types of serrations in the form of sinusoidal, square, and triangular shapes are cut into the trailing edge of the main element. The flow at Mach number 0.185 and the Reynolds number 2.51 million is calculated by numerical solution of incompressible Navier-Stokes equations using k-ϵ realizable turbulence model. Results show that the serration has exceptional positive effects on the aerodynamic characteristics of the system by generating vortices that modify the flow structure downstream of the main airfoil. All serrated models experience a reduction in drag coefficient compared to the baseline model at incidence angles before stall. Additionally, the maximum lift coefficients for all serrated models are increased. Among the serrated models, the sinusoidal serration exhibits the best performance with 6.8% increase in the maximum lift coefficient, a 10.6% decrease in the drag coefficient, and 2 degrees increase in the stall angle of attack of the wing-flap system compared to the baseline geometry. Moreover, the effect of wavelength on the performance of square shape serration is investigated and its aerodynamic advantages and disadvantages are presented.