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Article

Surface Air Movement: An Important Contributor to Ventilation of Isolated Subsurface Structures?

1
NorthWest Occupational Health & Safety, North Vancouver V7K1P3, BC, Canada
2
Programa de Engenharia Ambiental, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-972, Brazil
3
Escola Politécnica, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-972, Brazil
*
Author to whom correspondence should be addressed.
Infrastructures 2019, 4(2), 23; https://doi.org/10.3390/infrastructures4020023
Received: 13 April 2019 / Revised: 6 May 2019 / Accepted: 7 May 2019 / Published: 9 May 2019
This study reports on near-surface airspeed measured using a fast-responding thermoanemometer during an investigation of ventilation of an isolated subsurface structure induced by natural forces. Air speed changes continuously, rapidly, and unpredictably when assessed on the time base of one or two seconds. Zero, the most common air speed, occurred in almost all tests throughout the year but especially during cool and cold months. The most probable non-zero air speed, 10.7 m/min (35 ft/min), occurred in all tests. This air speed is below the level of detection by the senses. The number of zero values and the height of the peak at 10.7 m/min follow a repetitive annual cycle. Isolated subsurface structures containing manhole covers share the characteristics of Helmholtz resonators. Grazing air flow across the opening to the exterior induces rotational air flow in the airspace of a Helmholtz resonator. Rotational flow in the airspace potentially influences the exchange of the confined atmosphere with the external one. Ventilation of the airspace occurs continuously and without cost and is potentially enhanced by the unique characteristics of the Helmholtz resonator excited by surface air movement. These results have immense importance and immediate applicability to worker safety. View Full-Text
Keywords: repetitive annual pattern; confined space; isolated subsurface structure; near-surface airflow; fast-response thermoanemometer; velocity distribution repetitive annual pattern; confined space; isolated subsurface structure; near-surface airflow; fast-response thermoanemometer; velocity distribution
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MDPI and ACS Style

McManus, T.N.; Haddad, A. Surface Air Movement: An Important Contributor to Ventilation of Isolated Subsurface Structures? Infrastructures 2019, 4, 23. https://doi.org/10.3390/infrastructures4020023

AMA Style

McManus TN, Haddad A. Surface Air Movement: An Important Contributor to Ventilation of Isolated Subsurface Structures? Infrastructures. 2019; 4(2):23. https://doi.org/10.3390/infrastructures4020023

Chicago/Turabian Style

McManus, Thomas N., and Assed Haddad. 2019. "Surface Air Movement: An Important Contributor to Ventilation of Isolated Subsurface Structures?" Infrastructures 4, no. 2: 23. https://doi.org/10.3390/infrastructures4020023

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