Etude de la convection naturelle turbulente en cavité verticale différentiellement chauffée : Analyse des structures et des transferts turbulents

Abstract : Natural convection flows in confined spaces are often turbulent (large dimensions and/or temperature difference ). Improving the knowledge of this type of regime and of the associated heat and mass transfers seems, therefore, to be essential. This experirnental work studies heat transfer mechanisms using coupled and synchronized measurernents of temperature and velocity in a turbulent natural convection flow at high Rayleigh number (Ra1-1=I.2 x1011) in a differentially heated cavity with a vertical aspect ratio (height/width) of 4. Velocity measurernents are acquired by PIV and temperature is measured with K-type micro-thermocouple (0=12.7 μm). Both measurementsystems are synchronized using a BNC® pulse generator. Thermal boundary conditions of the adiabatic walls and post treatment of PIV data using an orthogonal decomposition based on the kinetic energy of the flow - POD - have been considered with caution. It makes possible, on the one hand, the experimental assessment of turbulent quantities like enthalpy fluxes and dimensionless nurnber (Prandtl, diffusivity ... ) and, on the other hand the estimation of the contribution of the other terms of Navier-Stokes equations (pressure gradient and source term). Finally a discussion on characteristic scales of the flow and a comparison with numerical simulations are provided.
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Pierre Belleoud. Etude de la convection naturelle turbulente en cavité verticale différentiellement chauffée : Analyse des structures et des transferts turbulents. Autre. ISAE-ENSMA Ecole Nationale Supérieure de Mécanique et d'Aérotechique - Poitiers, 2016. Français. ⟨NNT : 2016ESMA0005⟩. ⟨tel-01371487⟩

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