Investigation of a Rib Structure Effect on the Aerodynamic Performance of a Plain Flapped Symmetrical Airfoil

In this paper, two-dimensional computational fluid dynamics analyses were conducted to examine the rib effect on the performance of the NACA 0018 plain flapped airfoil. A mesh independence study was carried out and the Spalart-Allmaras turbulence model was selected for validation. Four various airfoil models were designed: M1 (airfoil without plain flap and rib structure), M2 (airfoil with rib structure), M3 (airfoil with a plain flap) and M4 (airfoil with a rib structure and plain flap). The performance of designed airfoils was calculated in terms of lift-to-drag (C_L/C_D) ratio. As a result, the plain flap significantly increased the lift coefficient (C_L) and drag coefficient (C_D). While the rib structure enhanced the aerodynamic performance of the non-flapped airfoil when the attack angle was greater than 12°, it increased the performance of the plain flapped airfoil at almost all attack angles. Furthermore, it was seen that the rib structure decreased C_D values of plain flapped airfoil at all attack angles and increased C_L values of plain flapped airfoil when the attack angle was greater than 2°.