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Simulation de jets d'air lobés pour l'optimisation des Unités Terminales de Diffusion d'Air

Abstract : The thesis deals with the numerical simulation of lobed air jets for the optimization of Air Diffusion Terminal Units for buildings. First is presented a comprehensive literature review of the air jets and of the passive means of flow control. The manuscript continues with the principles of modeling of turbulent flows. Based on the previous considerations, we discuss the simulation and analysis of the air lobed jets following three parts. The first part deals with the simulation of an air jet at very low Reynolds number (Reynolds 800) in the unsteady regime. In this study, we presented several test cases of simulation for a cross-shaped orifice jet that we have confronted with experimental results. From the quantitative point of view, the simulation of a quarter of the jet’s section has yielded reasonably good results for the global characteristics of the flow. In order to detect in a significant way the unsteadiness of the jet, it was necessary to simulate the entire jet, but this was done at the expense of the number of cells in the computational domain, which consequently leaded to inappropriate quantitative results. In the second part we simulated the same air flow but in the turbulent regime (Reynolds 3000). Seven turbulence models have been confronted with experimental results. We show the relevance of the RSM turbulence model (Reynolds Stress Model) for predicting the flow.The last part is dedicated to the simulation of turbulent air jet in interaction. This part is divided into three successive and complementary studies. The first one was dedicated to find which turbulence model can reproduce most relevant phenomena and variables to the concerned application. The conclusion is that none of the turbulence models was able to predict all the dynamic features of the lobed jet flows in interaction. However, of these models, SST appears to be significantly better for the prediction of the interaction of the jets, the global dynamical expansion and the entrainment of the ambient air when the flow is numerically resolved through the lobed diffuser. On the basis of relevant dynamic quantities well predicted by the SST turbulence model, we undertake in the following part an analysis of the influence of the geometry of the lobe on the ability of the flow to entrain. A rounded lobe is then found to be more advantageous than a lobe with right angles. The final study examines the effect of the arrangement and spacing of the lobed orifices on the global quantities of the flow. A geometric solution allowing to increase the transparency of the lobed Air Diffusion Terminal Unit is then proposed. This solution should be tested experimentally in real conditions, in the new full scale model room constructed at LEPTIAB.
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https://tel.archives-ouvertes.fr/tel-00818414
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  • HAL Id : tel-00818414, version 1

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Aliou Dia. Simulation de jets d'air lobés pour l'optimisation des Unités Terminales de Diffusion d'Air. Autre. Université de La Rochelle, 2012. Français. ⟨NNT : 2012LAROS360⟩. ⟨tel-00818414⟩

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