Drag Optimization Study of Variable Camber Continuous Trailing Edge Flap (VCCTEF) Using OVERFLOW

Abstract

This paper reports the results of a computational study that was conducted to explore the effect of various Variable Camber Continuous Trailing Edge Flap (VCCTEF) configurations on the lift and drag of a NASA Generic Transport Model (GTM) wing section at a span-wise location called the break station that marks a sharp change in the wing trailing edge slope. The OVERFLOW solver with the the one-equation Spalart-Allmaras (SA) turbulence model 1 and the two-equation (k − ω) Shear Stress Transport (SST) turbulence model 2 was first applied to a NACA0021 airfoil case and the results were compared with experimental data of Harris 3 and ARC2D results 4 . The comparison showed good agreement between earlier results 3,4 and the SA model. Therefore, SA model was used for all the simulations in this study. Design cruise condition at 36,000 feet at free stream Mach number of 0.797 and Reynolds number of 30.734x10 6 was simulated for an angle of attack (AoA) sweep from -3 deg. to 10 deg. Five VCCTEF configurations with varying camber in the flap region were considered along with an unmodified (no flap deflection) airfoil as the baseline case. Comparison of lift and drag corresponding to these configurations with baseline configuration (retracted flaps) showed a definite trend in the results. Although the baseline configuration produced the lowest lift at a given AoA among the set under investigation, it produces stall after about 5 deg AoA, whereas with the VCCTEF settings, stall occurs earlier between 3 and 4 deg AoA. The lift enhancement was significant with the extended flaps, but it was accompanied with a drag penalty, as expected. But, the lift versus drag L/D results showed that at the design cruise lift coefficient of 0.51, the L/D characteristics improved from the baseline to four of the five VCCTEF configurations. Among these four configurations, the configuration which reflects a parabolic-like camber is more optimal than the other three configurations in terms of improved L/D and well-behaved C p distribution. The lift prediction is compared against theoretical lift prediction from potential flow theory. Excellent agreement between computed and theoretical incremental lift is shown.

Optimized Off-Design Performance of Flexible Wings with Continuous Trailing-Edge Flaps

“…The flap system layout for this work is shown in Figure 12 and has a total of 16 flaps each with 3 segments adding up to 48 possible flap settings. Preliminary investigations 18 have suggested that a "circular deflection" of the three segments of a flap is most effective in cruise. This deflection pattern is illustrated in Figure 13, where 2 = 2 1 and 3 = 3 1.…”

Geometric Definition and Ideal Aerodynamic Performance of Parabolic Trailing-Edge Flaps

“…For example, the Air Force Research Lab has developed a variablecamber compliant wing (VCCW), capable of changing camber from a NACA 2412 to a NACA 8412 through the use of an embedded actuator [1,2]. A similar technology, currently under development at NASA, is the variable camber compliant trailing edge (VCCTE) [3,4], which can produce variable flap geometries from a series of incremental flap sections. Additionally, shape-memory alloy (SMA) technology can be used for actuation to produce changes to airfoil shape during flight [5].…”

Estimation of morphing airfoil shape and aerodynamic load using artificial hair sensors

“…The studies showed that highly flexible wing, if elastically shaped in-flight by active control of wing twist and bending, may improve aerodynamic efficiency through drag reduction during cruise and enhanced lift performance during takeoff and landing. 8 Nguyen and Ting 9 identified the flutter characteristics of the wing using a linear beam formulation and vortex-lattice aerodynamics. Their study also indicated the reduction of flutter boundary of the wing with increased structural flexibility.…”