Large Eddy Simulation of Air Escape through a Hospital Isolation Room Single Hinged Doorway—Validation by Using Tracer Gases and Simulated Smoke Videos

Saarinen, Pekka E.; Kalliomäki, Petri; Tang, Julian W.; Koskela, Hannu

The difference between the final AVM with combined door operation and passage on the other hand, and door operation alone on the other hand, gives the additional effect of a human passage on the total AVM. It is not, of course, equivalent to the AVM due to human passage in the absence of the door operation. The value of this difference was 0.54 m 3 in the measurements and 0.30 m 3 in the simulations. Our measurements with a sliding door, with much less disturbance by the door itself, resulted in additional AVM of 0.92 m 3 -0.56 m 3 = 0.36 m 3 generated by the passage [28, 35] . This suggests that the human wake is an important agent in air transport. Concerning the relative proportion of the air volume of one room, migrating into the other room, Choi and Edwards [29] obtained a percentage of 2.5 in the case of walking speed 1 m/s and in the absence of the door. This means an AVM of 0.98 m 3 . This result was obtained 6 s after the human stopped, which makes it approximately comparable with the final AVM in our case. Also, the human stopped at 3.2 m from the doorway, while in the present study it stopped already at the distance of 2 m. Taking into account the deceleration ramp in our simulation, the time from the moment the nurse passes the doorway to the moment the door is half-closed is 8.45 s. In the paper of Choi and Edward, the time from the moment the human passes the doorway to the moment the AVM is measured, is 9.2 s. Thus, the time of influence of the wake is nearly the same in both simulations. However, their rooms and doorway were smaller than in our study (39.2 m 3 against 56.4 m 3 and 1.74 m 2 against 2.23 m 2 ). Tang et al. [21] estimated a range of values for the flux of the wake induced by a moving human, being 0.08-0.23 m 3 /s, though this estimate does not appear to take into consideration how the flux behaves over time during the passage and after the nurse has stopped moving.