Optimisation of a variable sweep morphing wingtip

In recent years, there has been a great push to reduce emissions in all sectors, creating a drive in the aviation community to create more efficient aircraft. The efficiency of an aircraft can generally be increased by lengthening its wingspan, however the span for larger aircraft is limited by a maximum value set by airports. Due to this, some large aircraft, most notably the Boeing 777X, having folding wingtips which allow them to artificially reduce their wingspan to meet airport regulations, whilst retaining the efficiency benefits. On current aircraft, such folding wingtips are used purely to reduce span and are secured "open" during flight. Research has shown potential to make wingtip hinges active during flight to improve some of the aircraft's characteristics, through either passive (free/sprung hinge) or active (actuated) control at the hinges. Current research is underway to investigate hinging the wingtips vertically, with the aim of this project being to investigate alternative geometries and kinematics of such hinged tips. Variable sweep angle has for example been applied to the whole wing in various aircraft in the past, as it allows for efficient flight at both low and high speeds. The wingtip design will involve optimisation of the wing external geometry and hinge placement for a range of required flight conditions, aiming to create a wing with increased efficiency.

For aircraft with longer and more slender wings than a traditional aircraft, the wing structure has a lower bending and torsional stiffness, which leads to them demonstrating larger deformations in flight. When the deformations are significantly large, the deformed aircraft has different aerodynamic characteristics, creating a coupled problem. With very large deformations, non-linear structural models are used for the aircraft as they can simulate effects which are not present in a typical linear model, such as geometric stiffening and follower force effects. This structural and aerodynamic coupling can become very significant under some flight conditions, with effects ranging from undesirable noise to catastrophic structural failure or loss of control. The aerodynamic and structural coupling is known as aeroelasticity, and at Imperial College an open-source, non-linear solver has been created to simulate aircraft with such effects. During this project, new modules will be implemented and used on the existing tools to simulate the wingtip characteristics. The non-linear aeroelastic characteristics of the variable sweep wingtips on highly flexible wings will be analysed to ensure both static and dynamic stability across the flight envelope.

A common issue with current non-linear aeroelastic solvers is they are slow to run, and so are often not practical for use in a non-research environment. An additional aim of this project is to implement data-driven methods and models with such solvers, allowing for faster generation of data with minimal accuracy loss. This involves extracting the dominant features from the aircraft's response, truncating the less significant effects to create a greatly reduced-order model of the problem. This also opens the possibility of creating real-time models, which can be used onboard aircraft for use with a control system for more optimal control strategies. The preferred strategies to achieve this are to be investigated and developed.