Analysis of visitation frequency through particle tracking method based on LES and model experiment

Area of Science:

• Environmental Engineering
• Fluid Dynamics
• Indoor Air Quality

Background:

• Non-uniform ventilation efficiency necessitates localized measurement indices.
• Local ventilation efficiency relates domain-averaged concentration to exhausted air concentration.
• Air age theory links room-averaged concentration to contaminant mean staying time.

Purpose of the Study:

• To introduce and analyze Visitation Frequency (VF) and average staying time per visitation (Tp) for local domain contaminant analysis.
• To clarify the mechanism of domain-averaged concentration formation using VF and Tp.
• To investigate the relationship between VF, Tp, and local purging flow rate.

Main Methods:

• Utilized particle tracking method based on Large Eddy Simulation (LES) results.
• Employed Computational Fluid Dynamics (CFD) with LES for flow field analysis.
• Validated LES predictions with a precise model experiment.

Main Results:

• VF is significantly influenced by the local domain's position within the room's flow field.
• Tp characterizes the flow pattern properties within the local domain.
• In the studied room model with one supply and one exhaust, VF was 5.70 when the local domain occupied half the room, decreasing with smaller domains.

Conclusions:

• VF and Tp provide insights into contaminant transportation and domain-averaged concentration mechanisms.
• These metrics are crucial for understanding local air exchange and contaminant removal efficiency.
• The study highlights the importance of spatial distribution in ventilation effectiveness.