Numerical investigation of the effects of coupled radiative heat transfer on free turbulent jets of water vapor

Abstract : Radiation plays an important role in a broad range of thermal engineering applications comprising turbulent flows. The growing need for accurate and reliable numerical simulations to support the design stages of such applications is the main motivation of this thesis.Of special interest in this work are the free-shear flows and the fundamental understanding of how radiation can modify their fluid dynamics and heat trans- port as well as how their turbulence fluctuations can alter radiative transfer. The goal of this thesis is to provide high-fidelity data of turbulent free jets coupled with thermal radiation in order to develop and validate free-shear turbulent models accounting for coupling interactions. To this end, turbulent free jets are described by direct numerical simulations (DNS) coupled to a reciprocal Monte- Carlo method to solve the radiative transfer equation. The spectral dependency of the radiative properties is accounted for with an accurate Correlated-k (ck) method. The numerical study is carried out with state-of-the-art fidelity to be as representative as possible of an actual jet in a participating medium. The simulation is optimized in terms of processing time taking advantage of an acceleration method called Acoustic Speed Reduction and by injecting artificial turbulence to enhance inlet boundaries.Two direct simulations of heated jets coupled with thermal radiation are carried out. On the one hand, a heated jet with moderate radiation is simulated. The analysis of its high-fidelity coupled DNS data has allow to derive a new scaling law for the decay of the temperature profile. This scaling accounts for the effects of modified density due to moderate radiation. Moreover, it allows for distinguishing whether thermal radiation modifies the nature of heat transfer mechanisms in the jet developed region or not. On the other hand, a strongly heated free jet is computed in order to quantify the effects of radiation on mean temperature and velocity fields as well as on second order moments.Besides the coupled DNS data, a RANS solver for variable-density flows coupled with thermal radiation has been implemented during the course of this thesis. The goal is to directly quantify the accuracy of the existing turbulent models, and to identify key parameters for further modeling of coupling interactions.
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Jan Mateu Armengol. Numerical investigation of the effects of coupled radiative heat transfer on free turbulent jets of water vapor. Thermics [physics.class-ph]. Université Paris-Saclay; Universidade estadual de Campinas (Brésil), 2019. English. ⟨NNT : 2019SACLC052⟩. ⟨tel-02275920⟩

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