Numerical study of an unsteady confined thermal plume under the influence of gas radiation

Ying Wang (1) , Anne Sergent (2) , Didier Saury (3) , Denis Lemonnier (3) , Patrice Joubert (1)

1 LaSIE - Laboratoire des Sciences de l'Ingénieur pour l'Environnement - UMR 7356
2 LIMSI - Laboratoire d'Informatique pour la Mécanique et les Sciences de l'Ingénieur
3 COST - Convection, Optimisation, Systèmes Thermiques [Institut Pprime]

Influence of gas radiation on a thermal plume initiated by a linear heat source in a confined cavity is investigated through numerical simulations. A 2D pure convection case is first considered to validate the numerical code by comparing the critical Rayleigh number against literature results. Then, simulations are extended to 3D con­ ars much earlier for 3D case. Periodic solutions in time exhibit a stationary plane wave which is further broken in the chaotic regime. Finally, gas radiation is introduced at Ra = 1,2 10**7 by considering different gaseous media: on one hand, a gray gas model with various optical thicknesses, and on the other hand, a real gas model for humid air (air - H 2 O mixture). Results show a strong influence of the radiative transfer on flow regimes. By increasing the optical thickness, radiation tends to stabilize the plume and delays the onset of unsteadiness. Comparison of the time-averaged temperature and velocity distributions for the considered gas models indicates that gas radiation reduces the spatial spreading of the plume but has little effects on the kinetic field.

Mots clés: Real gas model; DNS; Transition to unsteadiness; Thermal plume; Convection-radiation coupling

Domaines: Physique [physics]; Mécanique des fluides [physics.class-ph]

Ying Wang, Anne Sergent, Didier Saury, Denis Lemonnier, Patrice Joubert. Numerical study of an unsteady confined thermal plume under the influence of gas radiation. International Journal of Thermal Sciences, 2020, 156, pp.106474:1-14. ⟨10.1016/j.ijthermalsci.2020.106474⟩. ⟨hal-02998148⟩