Surrogate-based robust design of asymmetric splitter plates for aerodynamic performance efficiency of flatback airfoils

Flatback airfoils are widely employed in the inboard regions of large wind turbine blades due to their structural advantages; however, their blunt trailing edges generate significant base drag and unsteady wake dynamics that degrade aerodynamic efficiency. While splitter plates reported in the literature are predominantly symmetric and center-mounted, this study introduces a surrogate-based optimization framework for the aerodynamic design of asymmetric trailing-edge (TE) splitter plates aimed to stabilize the wake and enhance aerodynamic performance. A parametric splitter geometry defined by length, inclination angle, vertical offset, and thickness is investigated for airfoils with 5% and 10% of chord TE thicknesses. Gaussian process regression models trained on Reynolds-averaged Navier–Stokes simulations are coupled with an expected improvement strategy to identify optimal configurations that enhance the lift-to-drag ratio. The results demonstrate that asymmetrically tuned splitter geometries can substantially improve aerodynamic performance by promoting base pressure recovery and suppressing unsteady wake interactions. Quantitatively, the optimized splitter for the airfoil with 10% TE thickness reduces drag by over 20% and increases the lift-to-drag ratio by more than 30% at the design Reynolds number. It also maintains robust off-design performance with lift-to-drag improvements of about 25%–28%, while the airfoil with 5% TE thickness exhibits more moderate gains of approximately 8%–9%. Unsteady simulations also reveal that the asymmetric splitters weaken shear-layer coupling and attenuate coherent vortex shedding, leading to a more stable wake structure over a range of operating conditions.