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Etude numérique d'hélices cycloïdales : Analyse des écoulements tourbillonnaires instationnaires et optimisation

Abstract : Nowadays, the variable-pitch turbines and propellers are extensively employed to many engineering equipment, such as the vertical-axis wind turbine, underwater propulsion system and unmanned air vehicle. As a novel type of variable-pitch devices, cycloidal propellers, comprising several blades oscillating with sinusoidal motions, have been attracting more attention. The principle of the cycloidal rotor includes two basic motions: one is the rotation based on the centre of the shaft and the other is the blade pitching motion over a pivot-point along the chord line. The lift and propulsive force of the cycloidal propeller is provided by the components of the lift and drag on the blades, due to the variation of the relative angle-of-attack. The flow structures inside the cycloidal propeller are extremely complicated, involving several kinds of blade-wake and wake-wake interactions and different vortices on the blade surfaces, which depends on the geometrical parameters and working conditions significantly. For a better design of such device, it is of great importance to understand the flow physics of the cycloidal propeller and how it affects the performance under different working conditions. In this thesis, the unsteady vortical flows over a two-bladed cycloidal rotor are simulated using the SST γ-(Re) ̃_θttransition model. The main contributions of the present work can be summarized as follows: (1) calibration of the SST γ-(Re) ̃_θt transition model over a single airfoil, in terms of the mesh distribution, inlet turbulence condition, correlations and parameters in the transition model, and then comparing the results with the experiments at different incidences and Reynolds numbers; (2) applying the optimized transition model to a cycloidal rotor at two advance coefficients, to investigate the internal flow structures in detail, mainly including the blade-wake interaction, wake-wake interaction, near-wall vo rtex flows and laminar-turbulence transition; (3) optimizing the cycloidal propeller, including the pitching kinematic, chord-to-radius ratio, pitch-pivot-point and blade profile, and explaining how the global performance changes at different Reynolds numbers and advance coefficients, based on the analysis of the performance of the single blade, forces (lift and drag), pressure coefficients and near-wall flows on two blades.
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Submitted on : Tuesday, May 31, 2022 - 5:00:12 PM
Last modification on : Friday, August 5, 2022 - 2:54:01 PM

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  • HAL Id : tel-03683567, version 1

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Lei Shi. Etude numérique d'hélices cycloïdales : Analyse des écoulements tourbillonnaires instationnaires et optimisation. Génie des procédés. HESAM Université, 2021. Français. ⟨NNT : 2021HESAE059⟩. ⟨tel-03683567⟩

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