Abstract
Sunlight impinging on an aircraft interacts with the shock waves that form due to the high-speed flow and produce an optical phenomenon comprising of a shadow and caustic pattern extending along the wing span. This direct natural shadowgraph feature is visible under particular observer, vehicle operation and illumination conditions. Despite similarities to simulations of traditional fluid flow visualisation images, the phenomenon has not been replicated in its entirety before this research. The capability to simulate the phenomenon in a realistic manner is a prerequisite for future research. This work will allow the relationship between the observed visual artefacts, and the trans/super sonic compressible flow over an aircraft, to be established.In this research, a computational framework to simulate the behaviour of light in compressible flow is developed. Underpinned by the discipline of geometrical optics and based on underlying computational fluid dynamics solutions, the framework is composed of physically accurate models of all of the elements of the shock wave shadow formation and visualisation. These are used to predict the flow field, replicate light scattering and digitally generate realistic shock wave shadow images.
In a fully tested working implementation, both natural and artificial (wind tunnel) shadowgraphy experiments are accurately reproduced. To obtain representative synthetic shockshadows, it is determined that light must reach the shock waves in a grazing incidence condition. Moreover, it is found that the computation of the final illumination distribution depends on the spatial sampling and on the radiant energy gathering characteristics used in an adaptive statistical density estimation method.
| Date of Award | 12 May 2022 |
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| Original language | English |
| Awarding Institution |
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| Sponsors | Engineering and Physical Sciences Research Council & Airbus (United Kingdom) |
| Supervisor | Dorian P Jones (Supervisor) & Ann L Gaitonde (Supervisor) |