Development of Morphing Fairing for Semi-Aeroelastic Hinge winglets

近年来，减少飞机排放越来越受到重视。减少民用飞机排放的一个广为人知的方法是增加翼展。这减少了机翼的诱导阻力，从而减少了燃料消耗。这种方法的两个主要限制是(1)机场登机口尺寸的限制和(2)对较长机翼的结构要求的增加。半气动弹性铰链的概念旨在通过折叠翼尖来绕过上述两个挑战，其中折叠轴与自由流方向成张开角度。翼尖的折叠使飞机在接近机场登机口之前缩短了机翼，而耀斑角度使机翼减少了机翼根部的最大阵风载荷。以前的文献研究表明，低折叠刚度、低阻尼、低质量以及高张角的翼尖可以获得最好的阵风载荷缓解。在物理实现这种装置时的挑战之一是机翼内侧机翼和翼尖之间的蒙皮不连续。这种表面的不连续性容易产生漩涡和随后的流动分离，这侵蚀了可折叠翼尖的一些空气动力学优势。关节周围的柔顺整流罩将缩小缝隙，同时允许翼尖折叠。这种整流罩可以是一个集成的主结构，也可以作为关节；或者是铰链关节周围的二次蒙皮，它只承担空气动力载荷。选择后者是基于空间效率和最小化折叠刚度以更好地减轻阵风载荷。本研究项目专注于(1)研究折叠机翼几何形状上蒙皮的行为，并确定优化所需特性的蒙皮的特性，(2)识别具有所需特性的蒙皮的结构，以及(3)在折叠翼尖装置上实现所识别的蒙皮结构。总而言之，总体研究问题可以概括为“基于顺应性的、刚度定制的、变形的流线型能够为具有半气动弹性铰链翼片的全尺寸商业客机提供什么好处？”

In recent years, increasing emphasis has been placed on reducing aircraft emissions. One of the well-understood approaches to reduce emissions in civil aircraft is to increase the wingspan. This reduces the induced drag of the wing, hence, the fuel consumed. Two major constraints in the way of this approach are (1) the limited airport gate sizes and (2) the increased structural requirement of a longer wing.The Semi-Aeroelastic Hinge concept is aimed at circumventing the above-mentioned two challenges by having a folding wingtip where the folding axis is at a flare angle outward to the freestream direction. The folding of the wingtip allows the aircraft to shorten the wing before approaching the airport gate and the flare angle allows the wing to reduce the maximum gust load on the wing root. Previous research in the literature has shown that the best gust load alleviation is achieved for wingtips with low folding stiffness, damping and mass along with a high flare angle.One of the challenges in the physical realisation of such a device is the discontinuity of the wing skin between the inboard wing and the wingtip. This discontinuity of the surface is prone to the generation of vortices and the subsequent flow separation which erodes some of the aerodynamic benefits of the foldable wingtip. A compliant fairing around the joint will close the gap while allowing for the folding of the wingtip. This fairing could be an integrated primary structure that also acts as the joint; or a secondary skin around a hinge joint, which only carries the aerodynamic load. The choice of the latter is based on space efficiency and minimising the folding stiffness for better gust load alleviation.This research project focuses on (1) studying the behaviour of the skin on a folding wing geometry and identifying the properties of the skin which optimise the desired characteristics, (2) identifying the architecture of skins that has the desired properties and (3) implementation of the identified skin architecture on a folding wingtip device.In summary, the overarching research question could be summarised as "What benefits can compliance-based, stiffness tailored, morphing fairings provide to full-scale commercial airliners with Semi-Aeroelastic Hinge winglets?".