Coupling Computational Fluid Dynamics Simulations and Statistical Moments for Designing Healthy Indoor Spaces

Abstract

Cross-contamination between occupants in an indoor space may occur due to transfer of infectious aerosols. Computational fluid dynamics (CFD) provides detailed insight into particle transport in indoor spaces. However, such simulations are site-specific. This study couples CFD with statistical moments and establishes a framework that transitions site-specific results to generating guidelines for designing “healthy” indoor spaces. Eighteen cases were simulated, and three parameters were assessed: inlet/outlet location, air changes per hour, and the presence/absence of desks. Aerosol release due to a simulated “sneeze” in a two-dimensional ventilated space was applied as a test case. Mean, standard deviation, and skewness of the velocity profiles and particle locations gave an overall picture of the spread and movement of the air flow in the domain. A parameter or configuration did not dominate the values, confirming the significance of considering the combined influence of multiple parameters for determining localized air-flow characteristics. Particle clustering occurred more when the inlet was positioned above the outlet. The particle dispersion pattern could be classified into two time zones: “near time”, <60 s, and “far time”, >120 s. Based on dosage, the 18 cases were classified into three groups ranging from worst case scenario to best case scenario.

A Review of Large-Eddy Simulation Cell Size Requirements for Indoor Flows

“…By selecting arbitrarily from RANS studies two could be mentioned, one that uses cell size close to the 75% quartile ∆ = 33 mm [70] and another one, which has a significantly smaller cell size in the domain ∆ = 0.08 mm [71]. Yet for large-scale Direct Numerical Simulation (DNS) ∆ = 3.15 mm [72] was used, which is fine for LES, though for DNS it could be coarse similarly to a two-dimensional flow study with ∆ = 18 mm [73]. The cell sizes are close to each other when using median values of ΔmeadianNFT = 13.9 mm, ΔmeadianDFT = 25 mm, and ΔmeadianTFT = 11.9 mm.…”

Numerical modeling of a sneeze, a cough and a continuum speech inside a hospital lift

“…In the case of occupancy by a standing up person, its respiration inhaled from the bottom contaminated air. Hoque and Omar [ 29 ] simulated a two dimension room to explore the best ventilation configuration, according to inlet an outlet height positions for an emitted cough. Pursuant to this study, for good ventilation paths, inlet and outlet must be in the same height, and avoiding as possible to set the inlet above the outlet.…”

A simplified tempo-spatial model to predict airborne pathogen release risk in enclosed spaces: An Eulerian-Lagrangian CFD approach

“…The place of disagreement in contradictory findings associated with the disease transmission are in numerous strands, including carriage process of pathogens with droplets and aerosols from an infected person to a new host [ 16 ], drying and evaporation processes of exhaled bioaerosols following with its properties (e.g., size, mucus), environmental conditions (e.g., relative humidity) [ 6 , 17 ], and number and size of released bioaerosols in each activity mode (i.e., respiration, sneeze, and coughs) [ 8 , 18 , 19 ]. As it has been broadly discussed in previous studies, one should add the importance of demographical characteristics (age, gender, ethnicity, etc.)…”