Temperature wall function adaptation for LBM-LES simulations of a hot wall jet developing in a room

  • Gresse, Teddy (Univ Lyon, INSA Lyon, CNRS, CETHIL, UMR5008, Villeurbanne, F-69621, France)
  • Merlier, Lucie (Univ Lyon, UCBL, INSA Lyon, CNRS, CETHIL, UMR5008, Villeurbanne, F-69621, France)
  • Jacob, Jérôme (Aix Marseille Univ, CNRS, Centrale Marseille, M2P2, UMR 7340, Marseille, 13451, France)
  • Kuznik, Frédéric (Univ Lyon, INSA Lyon, CNRS, CETHIL, UMR5008, Villeurbanne, F-69621, France)

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Airflows in a mechanically ventilated room are characterized by a combination of complex characteristics: wall interactions, vortices, buoyancy, etc… and the associated flow regimes can be either laminar, transient, or turbulent. Thus, the modeling of such flow is challenging and particularly the convective heat transfer at wall that is important for predicting building thermal behavior or thermal comfort. Standard wall functions are often used to simulate the convective heat transfer at walls. However, since the buoyancy effect is not considered in the standard wall function, the convective heat transfer is often underestimated, which in turn affect the prediction of the indoor air velocity and temperature distributions. A first way to correct the standard wall function is to adjust the wall Prandtl number [1]. As the wall Prandtl number decreases, the convective heat transfer increases. This method appears to be easy to implement but has no physical basis and lack universality. A second way is to use a new wall function accounting for the influence of buoyancy on heat transfer for the near-wall region [2]. The contribution proposes to perform Large Eddy Simulations (LES) based on the Lattice-Boltzmann Method (LBM) of an axisymmetric and hot jet developing in a room near a wall with the ProLB software ( and evaluate the two temperature wall functions adaptations compared to the standard wall function. The simulations are validated and calibrated using an extensive experimental data set of a full-scale mechanically ventilated test room called Minibat [3]. The first results show a significant improvement of the predicted profiles of air temperature with the adjusted wall function. The new wall function accounting for the buoyancy effects is still under study. [1] T. Zhang, H. Zhou and S. Wang, “An adjustment to the standard temperature wall function for CFD modeling of indoor convective heat transfer,” Building and Environment, 2013. [2] B. Chen, S. Liu, J. Liu, N. Jiang and Q. Chen, “A new wall function for indoor airflow with buoyancy effect,” Building and Environment, 2021. [3] F. Kuznik, “Experimental study of horizontal anisothermal axisymmetric jets developing near a wall: application to the numerical modeling of ventilated cavities (in French),” PhD Thesis, INSA, Lyon, 2005.