Browsing by Author "Changfoot, Donovan M"

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    Towards a hybrid CFD platform for investigating aircraft trailing vortices
    (2017) Changfoot, Donovan M; Malan, Arnaud G; Nordström, J
    This dissertation outlines the development of a parallel 3D hybrid finite-volume- finite-difference solver. As motivation for such a scheme, the specific application area under consideration is modeling the trailing vortices shed from the wings of aircraft under transonic flight conditions. For this purpose, the Elemental® finite volume code is employed in the vicinity of the aircraft, while the Essense finite difference software is employed to accurately resolve the trailing vortices. The former method is spatially formally 2nd order and the latter set to 6th order accurate. The coupling of the two methods is achieved in a stable manner through the use of Summation-by-Parts operators and weak imposition of boundary conditions through Simultaneous-Approximation-Terms (SBP-SAT). Accordingly, a special parallel SBP-SAT interface library is developed in Elemental®. In addition, the code is extended to impose boundary conditions in a weak manner via the SBP-SAT framework; as well as interface volume definitions changed to allow coupling with the 6th order code. The developed hybrid solver is successfully validated against analytical test-cases. This is followed by demonstrating its ability to model the flow field, including trailing vortex structures, around the NASA Common-Research-Model (CRM) under transonic flow conditions. Inviscid flow was assumed and the trailing vortices from both wing and horizontal stabiliser accurately resolved to 3 and 1 reference chords downstream of the lifting surface respectively. The robustness of the interface treatment is demonstrated by the smoothness of the flow solution across an interface boundary in the presence of high flow gradients and rapidly changing mesh topology. In addition, high vortex axial flow gradients were predicted while the vortex core speed is 6 % slower than free-stream.