Prediction of airflow and heat transfer in a mechanically ventilated room with Large-Eddy Simulations based on Lattice Boltzmann Method

Conditioned airflows in mechanically ventilated rooms are characterized by a combination of complex features such as interaction or impingement with walls, buoyancy near a surface or a flow at a different temperature. The associated flow regimes can be either laminar, transient, or turbulent. Modeling these flows and the associated heat transfers at walls is therefore challenging, but is of the utmost importance for predicting building thermal behavior, thermal comfort, and ventilation efficiency. This study aims to evaluate the capacity of a Large-Eddy Simulation (LES) approach using the Lattice Boltzmann Method (LBM) with adapted wall modeling to simulate axisymmetric and thermal jets generated by an air diffuser of complex design and developing near the ceiling of a full-scale test room. Simulation results are compared with detailed experimental data for the cases of an isothermal jet, a hot jet, and a cold jet in terms of mean velocity, temperature, and turbulence intensity profiles. The jet turbulence distribution is further analyzed by means of anisotropic invariant mapping and vortex visualization. The results show good qualitative and quantitative agreement between simulation results and experimental data. In particular, the simulated velocity and temperature profiles within the jets are consistent with measurements, and the air temperature in the room's central occupancy region is correctly estimated. Also, the main turbulent mechanisms in the jets' development zone are well captured. Thus, the chosen approach enables detailed, high-fidelity simulations of airflow and heat transfer in ventilated rooms to be performed efficiently.