Hybrid LES/RANS Model for Simulation of Particle Dispersion and Deposition

Abstract

Particle dispersion and deposition in a modeled room was investigated using the Lattice Boltzmann method (LBM) in conjunction with the hybrid RANS/LES turbulence model. For this new model a combination of LES and RANS models was used to reduce the computational cost of using the full LES in the entire domain. Here the near wall region was simulated by the RANS model, while the rest of the domain was analyzed using the LES model within the framework of the LBM. The k-ε turbulence model was applied in the RANS region. For using the k-ε model in the LBM framework, two additional distribution functions for k and ε were defined. For the LES region the sub-grid scale turbulence effects were simulated through a Smagorinsky model. To study the particle dispersion and deposition in the modeled room, particles with different sizes (diameters of 10nm to 10 μm) were investigated. The simulated results for particle dispersion and deposition showed that the predictions of the present hybrid method were quite similar to the earlier LES-LBM. In addition, the predictions of the hybrid model for the particle deposition and dispersion were closer to the LES simulation results compared to those of the k-ε model. It was shown that the Brownian excitation is very important for nanoparticles and the number of deposited particles for 10nm particles is higher than those for the larger 100nm and 1μm particles. The deposition rate for 10 μm particles is also high due to the inertial effects.