Numerical study of the lock-up phenomenon of human exhaled droplets under a displacement ventilated room

Naiping Gao, Qibin He, Jianlei Niu

Research output: Journal article publicationJournal articleAcademic researchpeer-review

36 Citations (Scopus)


This paper adopts an Eulerian-Lagrangian approach to investigate the lock-up phenomenon (or trap phenomenon) of human exhaled droplets in a typical office room under displacement ventilation (DV). A particle-source-in-cell (PSI-C) scheme is used to correlate the concentration with the Lagrangian particle trajectories in computational cells. Respiratory droplets with sizes of 0. 8 μm, 5 μm and 16 μm are released from a numerical thermal manikin (NTM). The influence factors including indoor temperature gradient, heat source configuration and exhalation modes are studied. It is found that large temperature gradient would result in trap phenomenon of small exhaled droplets (smaller than 5 μm). The intensive heat source near the NTM could help to transport the small droplets to the upper zone and decrease the concentration level in the trapped zone. Both nose-exhaled and mouth-exhaled small droplets would be trapped at the breathing height when temperature gradient is sufficiently high. However, the trap height of the droplets from mouth is a little bit higher. Because of large gravitational force, it is difficult for the thermal plume to carry 16 μm respiratory droplets to the upper zone.
Original languageEnglish
Pages (from-to)51-60
Number of pages10
JournalBuilding Simulation
Issue number1
Publication statusPublished - 8 Aug 2012


  • displacement ventilation
  • human exhaled droplets
  • Lagrangian simulation
  • thermal plume
  • trap phenomenon

ASJC Scopus subject areas

  • Building and Construction
  • Energy (miscellaneous)


Dive into the research topics of 'Numerical study of the lock-up phenomenon of human exhaled droplets under a displacement ventilated room'. Together they form a unique fingerprint.

Cite this