16:00
Movables
Chair: Raymond kolonay
16:00
30 mins
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Experimental and numerical assessment on the aeroelastic behavior of a NLF airfoil with oscillating control surfaces
Carlos Sebastia Saez, Mirko Hornung
Abstract: The potential based Doublet Lattice Method (DLM) is a state-of-the-art tool to model unsteady aerodynamic loads in the flutter analysis. However, it does not account for viscous or non-linear effects. In the subsonic regime, thickness and boundary layer effects may only play a minor role in aeroelastic analysis. This is no longer the case when oscillating control surfaces are involved. In these cases, DLM overpredicts the efficiency of the control surface, as it neglects the effects of an increasing boundary layer thickness and overpredicts the pressure distribution over the control surface. The unsteady flap hinge moment can deviate as much as 20% between theoretical and experimental results. Correcting DLM with higher fidelity methods or wind tunnel experiments can increase the accuracy of the flutter prediction if control surfaces are involved.
Most of the related studies are performed on a NACA0012 airfoil. The uncertainties regarding the effect of an oscillating natural transition location or a laminar separation bubble on the aerodynamic efficiency of a sailplane Natural Laminar Flow (NLF) airfoil due to oscillating control surfaces and the resulting hinge moments are still considerable.
The goal of this investigation is to reduce uncertainties in the aerodynamic behavior of a modern NLF airfoil due to flap oscillations and correct the pressure distributions predicted by lower-fidelity methods. Wind tunnel experiments at low turbulence intensities and CFD simulations with the Gamma transition model have been conducted to investigate the impact of an unsteady transition on the pressure distribution. The results are compared to DLM predictions and are used to correct the DLM pressure distribution.
The chosen correction method is based on a post-multiplication of the aerodynamics influence coefficient matrix by a correction matrix, formulated so that the pressure loads predicted by DLM are equal to the ones of the higher fidelity method.
The analysis of the pressure distributions shows good agreement between the experimental and CFD results. The pressure magnitude predicted by DLM shows the most significant deviations near the leading edge and the hinge line, demonstrating the need to correct the DLM results. The impact on the flutter results is analyzed with Nastran.
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16:30
30 mins
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Control surface sizing and design through integrated MDO approach: Enhancing load alleviation while preserving handling quality criteria
Daniel Muradas Odriozola, Sylvie Marquier, Joseph Morlier, Christian Gogu
Abstract: As part of ongoing efforts for cleaner and more efficient aviation, this research introduces a novel Multidisciplinary Optimization (MDO) strategy for the weight optimization of High Aspect Ratio (HAR) wings involving active load alleviation. The study focuses on implementing a Load Alleviation Function (LAF) to reduce wingbox structural loads during manoeuvres or gust encounters by redistributing lift inboard using movable control surfaces [1]. Building upon previous work [2], this MDO process aims to redefine control surface sizing and positioning for an optimised load alleviation while preserving the primary goal of ensuring effective aircraft manoeuvrability. An HAR wing concept is an enabler for enhancing the aircraft performance, however it is typically heavier than its lower aspect ratio counterpart. Additionally, it leads to greater flexibility in the wing, directly influencing the efficiency of the control surface and potentially leading to control surface reversal phenomena. The challenge thus lies in defining a control surface concept to allow a weight reduction through load alleviation thanks to the an optimal position and size of control surfaces, while simultaneously satisfying certification criteria for aircraft manoeuvrability across a diverse set of flight scenarios, including failure cases such as engine or actuator failure. To achieve this, an MDO approach is being considered in this work, intended to cover relevant Loads conditions and Handling Quality (HQ) criteria considered for certification, covering also overall aircraft design considerations such as the detrimental effect on Horizontal Tail Plane (HTP) weight impacted by the tuning of the Loads Alleviation. The implemented MDO approach considers the following disciplines, static aeroelastic analysis, discrete tuned gust encounter, aircraft manoeuvre trimming, HTP load monitoring, control surface reversal analysis, handling qualities efficiency assessment, and its associated validation between classic wing concept versus high aspect ratio.
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17:00
30 mins
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Continuous parametrisation of wing movable layout for design optimisation
Stefan de Boer, Jurij Sodja, Roeland De Breuker
Abstract: In line with recent advancements in aviation, which lead to more fuel-efficient
aircraft, this paper presents a novel continuous movable parameterisation methodology. The methodology takes advantage of the ability of the doublet lattice method (DLM) to describe aerodynamic forces using downwash. The movables are described in the continuous space using a downwash distribution generated using a B-spline surface. To demonstrate and assess the movable modelling methodology, the U-HARWARD aircraft model has been used, with the performance of the continuous parameterisation compared to a reference movable parameterisation for roll control, manoeuvre load alleviation and cruise performance. The results show that the continuous parameterisation can determine a downwash distribution that is at least equal in performance – during roll – or has better performance – for manoeuvre load alleviation and cruise performance – than the reference parameterisation. The continuous parameterisation showed a 3 percentage points improvement with respect to the reference parameterisation for manoeuvre load alleviation and a 2.4 percentage points improvement for the induced drag coefficient. The results in the paper demonstrated the successful application of a movable parameterisation methodology, which can be applied to an aircraft for which only the planform and initial structural parameters are known.
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17:30
30 mins
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Application of aeroelastic tailoring for control surface reversal
Evangelos Filippou, Jurij Sodja, Roeland De Breuker
Abstract: This research investigates the application of aeroelastic tailoring to enhance the post-control surface reversal regime on a mid-range aircraft. Conventionally, active Maneuver Load Alleviation (MLA) is achieved through control surface actuation, while passive MLA utilizes structural modifications at the material or layout level to exploit wing wash-out deformation. Previous studies have demonstrated the significance of high control effectiveness in active MLA and the limitations of composite tailoring in passive MLA due to roll control authority constraints which typically result in stiffer wings with moderate mass savings. The aeroelastic optimization framework PROTEUS, developed at TU Delft, is employed to enhance operation in the post-control surface reversal regime. This is done to capitalize on increased control authority and thus promote load alleviation. The approach taken in this study is to identify critical constraints and assess the advantages of this strategy while acknowledging the technology’s immaturity, particularly its challenges in maintaining roll control effectiveness in certain flight envelope sectors. The results demonstrate significant mass savings in active MLA within the post-control surface reversal regime compared to conventional active MLA and highlight the substantial impact of the cruise-twist constraint on enhancing this regime.
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