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Reliable and Adaptive CFD Framework for Airship Design

Abstract : This thesis is devoted to the modeling and the numerical simulation of unsteady, turbulent flows relevant to external aerodynamic applications. The proposed study aims at developing methods suited to incompressible, monophase and multiphase flows around various slender and non-slender bodies. The latter rely on the Variational Multiscale (VMS) stabilized finite element method, that introduces an a priori decomposition of the solution into coarse and fine scale components. The general idea is that only the large scales are fully represented and resolved at the discrete level, while the effect of the small unresolved scales is taken into account by means of consistently derived source terms proportional to the residual of the resolved scale solution. An automatic procedure is used to build complex meshes combining a multilayer inner region structured according to the boundary layer theory, and an external non-structured region refined using a VMS error estimator under the constraint of a fixed number of nodes. For cases involving several immiscible phases, an advanced level-set method is used to accurately follow the interfaces while accounting for surface tension effects. The coupling between these various components into a unified formulation, and their implementation in a context of high performance computing, make for the novelty and the main objective of this thesis. Several test-cases in two and three dimensions are presented to assess the accuracy and the robustness of the proposed methods. The solver is then used to analyze the aerodynamics of the Stratobus, a stratospheric airship designed by Thalès Alenia Space for a wide range of civilian and military operations. In the permanent regime, a rigid envelope assumption allows predicting the forces exerted on the structure in good agreement with the experiments. The effect of a lighter-than-air ballonet slosh located in the hull is also simulated to characterize the airship dynamics during take-off.
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  • HAL Id : tel-02890124, version 1

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Ghalia Guiza. Reliable and Adaptive CFD Framework for Airship Design. Mechanics [physics.med-ph]. Université Paris sciences et lettres, 2019. English. ⟨NNT : 2019PSLEM021⟩. ⟨tel-02890124⟩

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