Comparative CFD Analysis of Different Angles of Trailing-Edge Fowler Wing Flaps

This paper focuses on a case study to compare the performances of Fowler wing flaps that are used on the trailing edge of modern-day commercial airliners. The aim is to observe trends in coefficients of lift (C_l) and drag (C_d) with varying flap angles of release on a single-slotted Fowler flap and arrive at the most efficient flap configuration for flight. A series of two-dimensional analyses are carried out using computational fluid dynamics (CFD) to examine the flow separation and occurrence of stalls between the different angles of flap deflection. A two-equation, k-ω shear stress transport (SST) turbulence model is used as it helps in better prediction of flow separation and boundary layer studies. Since the study is carried out for such passenger carriers, the study focuses on the lower transonic ranges of Mach number 0.7-0.9 with a Reynolds number range of 400,000 to 500,000 considering a scaled-down model and upon taking inspiration from related literature. The flaps are analyzed at various angles of release (α) such as 0°, 15°, 25°and 50°, which are selected considering the angles that they are commonly deflected to during take-off and landing scenarios. A NACA0012 symmetrical airfoil is chosen with a fixed chord length for the wing and kept at 0° Angle of Attack (AoA) with subsequent trailing edge Fowler flaps employed for examination. A data-driven approach is followed for the investigation of characteristics represented by the different designs of the Fowler flap, thus typical lift curve plots (C_l vs α), drag plots (C_d vs α), and lift-to-drag ratio (C_l/C_d) plots (C_l/C_d vs α) graphs are presented to understand the comparative study. The results are discussed with respect to the data observed in the graphs and a viable conceptual configuration for the single-slotted Fowler flap is selected. This insight, research, and design have led to the development of the research paper and it is hoped that this comparative study can be used to conduct further research in the field of aeronautics.