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The influence of external wind in tunnels
Mälardalen University, School of Sustainable Development of Society and Technology.
University of Gävle.
2011 (English)In: The International Journal of Ventilation, ISSN 1473-3315, Vol. 10, no 1, 31-47 p.Article in journal (Refereed) Published
Abstract [en]

A model tunnel (approximately ten hydraulic diameters) with different designs of the tunnel mouth has been placed in a wind tunnel and has been subjected to the effects of external wind by varying thewind direction at the mouth of the tunnel. In the experimental oriented study pressures have been measured and the airflow has been made visible with smoke and by the sand erosion method (semolina).The relation between the flow ratio and the direction of the wind has been explored. When the wind is blowing parallel to the tunnel, the tunnel flow is about 70% of the reference flow (the undisturbed flow due to the wind through an area corresponding to the tunnel cross section). This result holds for the length of this tunnel. For longer tunnels it will decrease due to increased friction. When the angle at which the wind is blowing increases, the tunnel flow decreases. The pressure measurements made it possible to quantify some of the phenomena which were observed in the visual trials. A large under-pressure was measured just outside the mouth of the model tunnel on the side of the tunnel corresponding to the separation in the visual trials. In front of the tunnel, a pressure increase due to thebraking of the airflow was measured. The position of the pressure increase moved depending on the internal resistance in the tunnel. If the resistance in the model tunnel was high, the over-pressure in front of the mouth of the tunnel was higher and further from the opening. When the internal resistance was reduced (corresponding to e.g. a very short tunnel) the over-pressure decreased and moved closer to the tunnel opening.

Place, publisher, year, edition, pages
2011. Vol. 10, no 1, 31-47 p.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:mdh:diva-14588ISI: 000290880700003OAI: oai:DiVA.org:mdh-14588DiVA: diva2:525397
Available from: 2012-05-08 Created: 2012-05-07 Last updated: 2012-10-23Bibliographically approved
In thesis
1. Brandgasflöden vid tunnelbränder: Temperaturskiktning vid tunnelbränder och vindorsakade luftrörelser i tunnlar
Open this publication in new window or tab >>Brandgasflöden vid tunnelbränder: Temperaturskiktning vid tunnelbränder och vindorsakade luftrörelser i tunnlar
2012 (Swedish)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Today more and more underground facilities and tunnels are built. Fires in tunnels and underground facilities can lead to catastrophic consequences for users and owners. Fires in tunnels are complex phenomena and are in many cases difficult to calculate or simulate.  Therefore the knowledge and design must primarily be based on information obtained from full and model scale tests.

 

The convective air flow is crucial in an emergency situation but can also affect other installations such as fans. The thesis focuses on these two research areas.

 

The stratification of the convective flow (temperature stratification) and the smoke is a very important part of the safety design. There are methods available to determine the temperature stratification. Based on a method proposed by Newman previously performed fire tests, both in full and model scale were analyzed. One aim is to obtain simple expressions for hand calculations of the temperature conditions inside a tunnel in case of a fire. The thesis presents a summary of simplified semi-empirical expressions for calculations of fire phenomena in tunnel fires. A key factor for the resulting air velocity in the tunnel is the external wind effects. Based on previous work and a new study, semi-empirical expressions for calculations of wind effects in tunnels are presented.

 

The thesis also presents detailed studies of air motion conditions in and around various tunnel entrances at different wind directions and pressures. Analyses were carried out with different pressure measurement and visualization experiments.

 

The following results are presented in the thesis:

 

  • Reasons and arguments for a risk-based approach for fire design of tunnels

 

  • A compilation and analysis of full-scale and model tests from a temperature and smoke stratification perspective according to a method proposed by Newman

 

  • A revised correlation model for temperature calculations based on two full-scale experiments and a model test

 

  • Simplified correlations and graphs for the calculation of external wind effects in tunnels

 

  • Enhanced analysis of wind effects in tunnels
Place, publisher, year, edition, pages
Västerås: Mälardalen university, 2012. 65 p.
Series
Mälardalen University Press Licentiate Theses, ISSN 1651-9256 ; 151
National Category
Engineering and Technology
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-14590 (URN)978-91-7485-069-7 (ISBN)
Presentation
2012-06-05, Gamma, Mälardalens högskola, Västerås, 13:00 (Swedish)
Opponent
Supervisors
Available from: 2012-05-08 Created: 2012-05-08 Last updated: 2012-06-07Bibliographically approved

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