scholarly journals Evaluation of Natural Ventilation on Temperature and Pressure Distribution in a Road Tunnel Fire with Vertical Shaft

2015 ◽  
Vol 55 ◽  
pp. 79-85
Author(s):  
I. Benabdelaziz ◽  
M. Bouterra ◽  
Afif El Cafsi ◽  
A. Belghith
Keyword(s):  
Natural Ventilation ◽  
Pressure Field ◽  
Reduction Rate ◽  
Vertical Shaft ◽  
Road Tunnel ◽  
Urban Road ◽  
Eddy Simulation ◽  
Tunnel Fire ◽  
Large Eddy ◽  
Temperature And Pressure

This paper has analysed the influence of plug-holing on thermal and pressure field evolution in urban road tunnel fires with vertical shaft by Large Eddy Simulation (LES). Results show that the temperature reduction rate is about 70 % at the tunnel half and it increases about 80 % at the ceiling level. The pressure field is characterized by a pseudo-periodic behavior which reaches a maximum reduction rate (78 %) in case of natural ventilation. The numerical tool used is FDS (version 5).

scholarly journals EFFECTS OF VERTICAL SHAFT GEOMETRY ON NATURAL VENTILATION IN URBAN ROAD TUNNEL FIRES

2014 ◽  
Vol 20 (4) ◽  
pp. 466-476 ◽  
Author(s):  
Jie Ji ◽  
Chuan Gang Fan ◽  
Zi He Gao ◽  
Jin Hua Sun
Keyword(s):  
Large Scale ◽  
Natural Ventilation ◽  
Boundary Layer Separation ◽  
Vertical Shaft ◽  
Road Tunnel ◽  
Urban Road ◽  
Tunnel Fires ◽  
Negative Effect ◽  
Angle Connection ◽  
The Right

A set of burning experiments were conducted to investigate the effect of vertical shaft geometry on natural ventilation in urban road tunnel fires. Results show that using vertical shafts to discharge smoke leads to a boundary layer separation near the right-angle connection of the shaft and the tunnel ceiling. In a low shaft, the turbulent-boundary-layer separation phenomenon causes relatively large-scale vortexes and restricts smoke from being exhausted, resulting in a negative effect on natural ventilation. Replacing the right-angle connection with the bevel-angle connection was proposed to split one separation point into two separation points, to attenuate the negative effect. The detailed characteristics of the separation phenomenon were analysed and the proposition was verified by Large Eddy Simulation. Results show that there are no relatively large-scale vortexes in shafts with bevel-angle connections, resulting in improved natural ventilation effectiveness. For lower shafts, the advantage of using the bevel-angle connection is more significant, and for shafts of the same height, the mass flow rate of smoke discharged by shafts with the bevel-angle connection increases up to 1.5 times of that by shafts with the right-angle connection. For relatively high shafts, it is about 1.2 times.

scholarly journals ICCM2015: A Comparison of RANS and LES Computational Methods in Analyzing Ventilation Flow Through a Room Fitted with a Two-Sided Windcatcher

2017 ◽  
Vol 14 (03) ◽  
pp. 1750021 ◽  
Author(s):  
A. Niktash ◽  
B. P. Huynh
Keyword(s):  
Natural Ventilation ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Interior Space ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Through ◽  
Cfd Method ◽  
Good Agreement

A windcatcher is a structure for providing natural ventilation using wind power; it is usually fitted on the roof of a building to exhaust the inside stale air to the outside and supplies the outside fresh air into the building interior space working by pressure difference between outside and inside of the building. In this paper, the behavior of free wind flow through a three-dimensional room fitted with a centered position two-canal bottom shape windcatcher model is investigated numerically, using a commercial computational fluid dynamics (CFD) software package and LES (Large Eddy Simulation) CFD method. The results have been compared with the obtained results for the same model but using RANS (Reynolds Averaged Navier–Stokes) CFD method. The model with its surrounded space has been considered in both method. It is found that the achieved results for the model from LES method are in good agreement with RANS method’s results for the same model.

Wind-Driven Natural Ventilation in an Areaway-Attached Basement with a Single-Sided Opening for Residential Purposes

2011 ◽  
Vol 383-390 ◽  
pp. 5344-5349
Author(s):  
Zhen Bu
Keyword(s):  
Natural Ventilation ◽  
Ventilation Rate ◽  
Navier Stokes ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Effective Ventilation ◽  
The Mean ◽  
Ventilation Rates ◽  
Les Model ◽  
Good Agreement

This paper discusses the sustainability of the areaway-attached basement concept with the attentions focused on wind-driven single-sided natural ventilation. First, numerical simulations were performed on an areaway-attached basement with a single-sided opening. Two CFD approaches: Reynolds averaged Navier-Stokes (RANS) and large-eddy simulation (LES) were used and compared with the previous experimental results of effective ventilation rate. A good agreement between the measurement and LES model was found and RANS model tends to underestimate the ventilation rates. Furthermore, Based on LES with the inflow turbulent fluctuations, the mean airflow patterns within and around the areaway-attached basement was investigated for different wind incidence angles to examine the influences of wind direction on ventilation performances.

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