Development of Morphing Fairing for Semi-Aeroelastic Hinge winglets

近年来，人们越来越重视减少飞机排放。减少民用飞机排放的一个众所周知的方法是增加翼展。这减少了机翼的诱导阻力，因此，减少了燃料消耗。这种方法的两个主要限制是（1）有限的机场登机口尺寸和（2）更长机翼的增加的结构要求。半气动弹性铰链概念旨在通过具有折叠翼尖来规避上述两个挑战，折叠翼尖的折叠轴线在自由起落方向向外的张开角处。翼尖的折叠允许飞机在接近机场登机口之前缩短机翼，并且外展角允许机翼减小翼根上的最大阵风载荷。文献中以前的研究已经表明，最佳的阵风载荷减缓是在翼尖具有低折叠刚度、阻尼和质量沿着和大张开角的情况下实现的。这种装置的物理实现的挑战之一是内侧机翼和翼尖之间机翼蒙皮的不连续性。表面的这种不连续性易于产生涡流和随后的流动分离，这会侵蚀可折叠翼尖的一些空气动力学益处。接头周围的柔性整流罩将关闭差距，同时允许翼尖折叠。该整流罩可以是一个集成的主结构，也可以作为接头;或者是围绕铰链接头的次蒙皮，它只承载气动载荷。后者的选择是基于空间效率和最小化折叠刚度以更好地减缓阵风载荷。本研究项目的重点是（1）研究折叠机翼几何形状上蒙皮的特性，并确定优化所需特性的蒙皮特性，（2）识别具有所需特性的蒙皮结构，以及（3）在折叠式翼尖装置上实现所识别的蒙皮结构。这个首要的研究问题可以概括为：“对于采用半气动弹性铰链式小翼的全尺寸商用客机来说，基于柔度的、刚度量身定制的、变形的整流罩能够带来什么样的好处呢？".

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?".