Variable Camber Continuous Trailing Edge Flap Research Articles

Actuator energy and drag minimization of a blended-wing-body with variable-camber continuous trailing-edge flaps

This article conducts a multiobjective optimization study for minimizing both the actuator energy and the total drag of a NASA aircraft, the Blended-Wing-Body (BWB), during cruising, by using the three-segment Variable-Camber Continuous Trailing-Edge Flap (VCCTEF) proposed by NASA. The metric for the electric drive actuators' energy for the BWB during cruising is characterized by summing the absolute hinge moments for all actuators. A local minimum is easily obtained for the optimization problem with a least absolute sum cost function when using a gradient-based optimizer. The minimization of the total actuator energy is converted to a linear programming problem by treating the absolute hinge moments as design variables. The induced and profile drags are considered to be the largest two contributions to the total drag. Design variables for the flap rotations and the absolute hinge moments with different orders of magnitude are scaled with respect to their maximum bounds in the optimization study to avoid numerical problems. Different VCCTEF configurations of varying deflection profiles and degrees of actuation independence and traditional flaps are studied and their performance is compared. For the BWB with four representative fuel levels, 80, 50, 20 and 0% of the maximum fuel loads, all during cruising, multiobjective optimization studies show that the VCCTEF with three individual segments can achieve a minimal total drag for the BWB while requiring a minimal total actuator energy to maintain its optimal shape for the minimal total drag.

Numerical Study of Variable Camber Continuous Trailing Edge Flap at Off-Design Conditions

Numerical simulations are performed to study the outboard airfoil of advanced technology regional aircraft (ATRA) wings with five different variable camber continuous trailing edge flap (VCCTEF) configurations. The computational study aims to improve the aerodynamic efficiency of the airfoil under cruise conditions. The design of outboard airfoil complies with the hybrid laminar flow control design criteria. This work is unique in terms of analysis of the effects of VCCTEF on the ATRA wing’s outboard airfoil during the off-design condition. The Reynolds–Averaged Navier–Stokes equations coupled with the Spalart-Allmaras turbulence model are employed to perform the simulations for the baseline case and VCCTEF configurations. The current computational study is performed at an altitude of 10 km with a cruise Mach number of 0.77 and a Reynolds number of 2.16 × 107. Amongst all five configurations of VCCTEF airfoils studied, a flap having a parabolic profile (VCCTEF 123) configuration shows the maximum airfoil efficiency and resulted in an increase of 6.3% as compared to the baseline airfoil.

Optimization of Variable-Camber Continuous Trailing-Edge Flap Configuration for Drag Reduction

The variable-camber continuous trailing-edge flap is a novel control surface technology designed to serve as an aeroelastic wing shaping control device. Capable of minimizing drag throughout an aircraft flight envelope, use of the variable-camber continuous trailing-edge flap technology is examined on a flexible-wing transport aircraft configuration known as the NASA generic transport model. Drag reduction studies at various flight conditions are conducted in order to examine the performance of different flap configurations with selected camber deflection profiles. Rapid optimization of the design space is achieved by using aerodynamic–structural modeling based on a vortex lattice method coupled with transonic small disturbance and integral boundary-layer solutions. The begin cruise optimization results show that a parabolic flap deflection profile configuration with three-cambered-segments achieves the largest drag reduction of 8.4% as compared to a clean wing configuration. The configuration is used to run additional optimizations measuring performance benefits at different flight conditions including 20% fuel end cruise, a design lift coefficient, and a Mach overspeed condition. The optimization framework and initial results produce insights that can be used to refine the optimization of variable-camber continuous trailing-edge flap configurations with higher-fidelity aerodynamic tools.

Robust Optimization of Variable-Camber Continuous Trailing-Edge Flap Static Aeroelastic Action

A robust optimization method is described in this paper, focusing on the optimization of a variable-camber continuous trailing-edge flap system for drag reduction in transonic cruise. The variable-camber continuous trailing-edge flap, through the rich combination of shapes it can attain, has the potential to provide greater design and operation freedom than conventional flap systems as well as greater efficiency in drag reduction and performance improvement. The deformation shape optimization of such a system, however, when based on rigorous computational fluid dynamics simulations, presents a significant computational challenge because of the high cost of repetitive analyses required. The construction of surrogate models and their use in the optimization process is one common way to tackle this challenge. Here, stochastic kriging is used, extending the commonly used deterministic kriging. Accounting for the intrinsic uncertainty of data, stochastic kriging and the optimization based on it are well suited for addressing uncertain flight conditions as well as math modeling limitations. An optimization process for the variable-camber continuous trailing-edge flap system that couples shape synthesis with high-fidelity aerodynamic simulations, accounting for static aeroelastic interactions and load distribution constraints, is presented. A potential for robust optimal drag subject to flight Mach number uncertainties is shown.

Static and Dynamic Aeroelastic Tailoring with Variable-Camber Control

This paper examines the use of a variable-camber continuous trailing-edge flap system for aeroservoelastic optimization of a transport wing box, the Common Research Model. Along with patch-level structural wing-box design variables, the quasi-steady and unsteady motions of the flap system are used as design variables, for maneuver load alleviation, cruise fuel burn reduction, and active flutter suppression. The resulting system is able to minimize structural weight and/or fuel burn while satisfying constraints upon elastic stresses, panel buckling, actuator hinge moments, flutter margins, actuator work, and control cost metrics. Limitations to this success are imposed by including load cases where the actuation system is not active (open-loop) in the optimization process. Large open-loop safety factors, for either maneuver loads or flutter, dilute the importance of the closed-loop actuation mechanism, whereas small open-loop safety factors may produce an overly flexible wing, prone to failure. Similar tradeoffs between system performance and actuator work constraints are provided. A final theme of the paper explores aeroelastic performance penalties that may arise if the shapes available to the variable-camber actuation system are limited (i.e., if certain control segments are linked together).