Numerical investigation of effects of gurney flaps on aerodynamic performance of multi-element airfoils

The 2D unsteady Reynolds-averaged Navier-Stokes equations together with the two-equation shear stress transport (SST) k-ω turbulence model are applied to the multi-block structured grids of a C-H type to investigate the effects of various Gurney flaps (GF) and their geometry parameters on the aerodynamic performance of multi-element airfoils for different flap riggings, including the main GF, the flap GF and the combination GF. The numerical results for different flap riggings of the multi-element airfoil show that the impact of the main GF mainly depended on the slot parameters. By reducing the adverse pressure gradient, the main GF could effectively eliminate flow separation on the flap when it is in a non-optimum position; therefore it could be used to re-optimize the slot parameters. The influence of the flap GF on the baseline configurations with different flap riggings is nearly identical. The lift coefficient and nose-down pitching moment coefficient are significantly increased in non-linear variation, but the drag coefficient changed little if the height of the flap GF is appropriate. In the linear region the combination GF on the main element and flap is approximately a linear combination of the changes caused by the two individual GFs.