09:40
Aeroservoelasticity 2
Chair: Cedric Liauzun
09:40
30 mins
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Wing shape control on the D150 model with aspect ratio tradeoffs for fuel efficiency improvement
Fanglin Yu, Milán Barczi, Carlos Sebastia Saez, Béla Takarics, Yasser Meddaikar, Mirko Hornung
Abstract: In the scope of FLIPASED (Flight Phase Adaptive Aero-Servo-Elastic Aircraft Design Methods) project, this work focus on wing shape control on the D150 model with the primary goal of enhancing fuel efficiency. The model represents a market-demanding short-tomedium-range aircraft type.
Throughout the aircraft's mission, the fuel stored in the wing is gradually consumed, leading to changing wing loading and varying lift distributions due to aeroelastic effects. Typically, wings are designed for intermediate mass cases. As a result, the aerodynamics of the aircraft during off-design mass conditions are suboptimal. Wing shape control plays a crucial role in such scenarios, restoring optimal lift distribution via trailing edge control surfaces and thereby improving overall aerodynamic performance.
For an accurate assessment of wing shape control effects, it is essential to model drag. Given the imperative for swift calculations in the MDO process, following potential theory-based methods are employed.
a. Vortex Lattice Method (VLM) based near-field implementation: AVL, serving as a aerodynamic solver, is coupled with the MSC.Nastran structural solver to account for aeroelastic effects.
b. Doublet Lattice Method (DLM) based far-field implementation: The induced drag is computed on the Trefftz plane situated downstream of the aircraft, using the span-wise lift distribution which is derived from MSC.Nastran and projected onto the Trefftz plane.
c. 3D Panel Method based implementation: In contrast to the VLM/DLM methods mentioned earlier, which model the wing as a flat panel, the software Panukl models the wing using a 3D panel geometry, which can account for camber, jig twist, and thickness.
Furthermore, aircraft with varying aspect ratios (AR), spanning from 9.4 (baseline case) to 18.4, will be investigated, to assess the drag reduction impact in both the current aircraft configuration and potential future high AR wings. The assessment will extend to the evaluation of aircraft range to demonstrate improvements in fuel efficiency.
The preliminary results indicate a potential 2% drag reduction for the baseline model. Given the increased flexibility in high AR wings, it is expected that the impact could be even more pronounced. Consequently, wing shape control emerges as a crucial solution for the near-term enhancement of the current aircraft configuration without necessitating significant structural or aerodynamic design changes. This becomes particularly relevant in light of growing concerns about the climate impact of the aviation sector and the pressing need for immediate actions to curb CO2 emissions.
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10:10
30 mins
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Automated Tuning of a Baseline Flight Control System with Maneuver Load Alleviation for an Energy-Efficient Passenger Airplane
Till Strothteicher, Nicolas Fezans
Abstract: The aeroelastic design process of modern aircraft concepts involves the airframe sizing based on sizing loads, which are identified through simulation of selected load cases, e.g., gust encounters or maneuvers. Alleviation of the sizing loads offers potential for lightweight construction and thus an improved aircraft efficiency. Load alleviation concepts are investigated in the SE²A cluster employing an aeroelastic simulation framework for an energy-efficient passenger aircraft [1].
Generally, for the inboard portion of the wing, sizing loads are defined by the gust and maneuver loads. An active Gust Load Alleviation (GLA) system has been developed in [2]. To further reduce the sizing loads, the maneuver loads need to be lowered as well. For this purpose, an active Maneuver Load Alleviation (MLA) function is applied here. It mitigates the bending moment at the wing root by shifting the lift distribution along the wingspan towards the symmetric plane.
Modern passenger aircraft are typically equipped with a flight control system including a flight control law. The dynamic loads depend on said law, which is not yet considered in [1]. In order to simulate the dynamic load cases more accurately, a representative flight control law is designed and added to the loop. On this basis, the effectiveness of the MLA function is investigated.
Decreased sizing loads allow for a redesign of the airframe, which alters the aircrafts flight dynamics, in turn necessitating an adjustment of the flight control law. The interdependence implies that the Multidisciplinary Optimization (MDO) loop of both the flight control law and the structure must be iterated, which is only feasible if their design is fully automated. Hence, this work presents a practical approach to the multi-objective tuning of flight control laws for the automated design of a representative C* Control Augmentation System (CAS) including an active MLA function for a flexible aircraft. A comprehensive closed-loop performance analysis based on a linear model is conducted to validate the control design approach, regarding robustness and aeroelastic stability among others. Finally, the controller is evaluated for the nonlinear aeroelastic flight dynamics model [1].
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