Modeling of indoor airflow and dispersion of aerosols using immersed boundary and random flow generation methods

Abstract

Numerical modeling of environmental flows involves complex geometry, moving bodies, multi-phase flow, and buoyant jet effects. An in-house CFD code has been developed using finite volume and immersed boundary methods. The transport and dispersion of virus-laden aerosols in a ventilated room is investigated by this numerical code. The uniqueness of this numerical code is that it can efficiently compute small-scale turbulent flow in which most commercial CFD software will suffer from large numerical error. Random flow generation (RFG) [33] is an ideal choice for small-scale turbulence for low-Reynolds number flow in a ventilated room. In addition, Lagrangian stochastic (LS) walk model is applied to directly compute probability density function (PDF) of aerosols and estimate the risk factor of aerosol dispersion from a point source. The present study focuses on aerosols with small diameter (<10 μm) in which the effects of evaporation on the dispersion of aerosols could be neglected. Different location of aerosol sources and a typical ventilation layout are discussed in detail. The numerical results with PDF yield more useful quantitative information to assess the risk area of virus transport in a ventilated room than that shown in random trajectories of particles as widely reported in the literature. This study provides valuable information for ventilation control strategies with respiratory protection, such as enhanced air exchange, air filtration rate, and improved airflow patterns to reduce indoor infection risk via airborne virus laden droplets.