Research Article Indoor/Outdoor Airflow and Air Quality
In hospital isolation rooms, door operation can lead to containment failures and airborne pathogen dispersal into the surrounding spaces. Sliding doors can reduce the containment failure arising from the door motion induced airflows, as compared to the hinged doors that are typically used in healthcare facilities. Such airflow leakage can be measured quantitatively using tracer gas techniques, but detailed observation of the turbulent flow features is very difficult. However, a comprehensive understanding of these flows is important when designing doors to further reduce such containment failures. Experiments and Computational Fluid Dynamics (CFD) modelling, by using Large-Eddy Simulation (LES) flow solver, were used to study airflow patterns in a full-scale mock-up, consisting of a sliding door separating two identical rooms (i.e. one isolation room attached to an antechamber). A single sliding door open/ hold-open/ closing cycle was studied. Additional variables included human passage through the doorway and imposing a temperature difference between the two rooms. The general structures of computationally-simulated flow features were validated by comparing the results to smoke visualizations of identical full-scale experimental set-ups. It was found that without passage the air volume leakage across the doorway was first dominated by vortex shedding in the wake of the door, but during a prolonged hold-open period a possible temperature difference soon became the predominant driving force. Passage generates a short and powerful pulse of leakage flow rate even if the walker stops to wait for the door to open.
isolation room CFD simulation LES tracer gas smoke visualization
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This study was mainly funded by the Finnish Funding Agency for Innovation (TEKES, grant number 40301/10).
Video 1. Simulated vorticity z-component near the doorway on the horizontal plane 1 m above the floor during the door-alone cycle. Negative vorticity means clockwise and positive counter-clockwise rotation. Horizontal component of flow direction is indicated by arrows with constant length.
Video 2. Simulated smoke video combining two different smoke visualizations, and the corresponding experimental smoke videos.
Video 3. Updated video 1, after addition of passage and rescaling. The inlet in the upper left corner shows the vortex cores as illustrated by drawing two isosurfaces 150 s-2 and 500 s-2 of the absolute value of the second invariant of the velocity gradient tensor. Door-generated vortices are too weak to be seen in this scale.
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