Simulation numérique et modélisation d’écoulements tridimensionnels instationnaires à surface libre. Application au système bateau-avirons-rameur

Abstract : The thesis focuses on the two flows occurring in rowing,around the boat and the blade, and on interactions with theboat-oars-rower system. The first flow is unusual in hydrodynamics because of the large surge and secondary motions. The complexity of the second one comes from the unsteadiness and the free surface deformation. The goal is to set up efficient and accurate numerical methods to reproduce these flows and then to validate them for the purpose of analysis and optimisation of the performance in rowing.Those unsteady computations with free surface are cost lyin resources for RANS codes. A sub-cycling algorithm was developed and validated on several test cases, allowing to decrease the CPU time by a factor of 3 to 4, without loss of accuracy. It is compatible with mesh deformation and automatic grid refinement. Two experimental databases are exploited for each flow in order to validate the frame of simulation. For the flow around the blade, an in-situ campaign and a more controlled one conducted in laboratory, are used. In both cases, the profiles of the efforts are well captured, considering the cumulative uncertainties linked to the indirect measurement of the blade kinematics relative to the water. For the skiff in unsteady state, the fluctuating forces are well captured, in terms of amplitudes and phases, for typical frequencies. Unexpected errors (around10%) are observed for the mean value and remain unexplained for now. The structure of a co-simulation between the resolutions of the flows and the resolution of the dynamics of the multibody system is initiated.
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Yoann Robert. Simulation numérique et modélisation d’écoulements tridimensionnels instationnaires à surface libre. Application au système bateau-avirons-rameur. Mécanique des fluides [physics.class-ph]. École centrale de Nantes, 2017. Français. ⟨NNT : 2017ECDN0023⟩. ⟨tel-02184050⟩

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