scholarly journals Natural Ventilation of a Small-Scale Road Tunnel by Wind Catchers: A CFD Simulation Study

Atmosphere ◽  
2018 ◽  
Vol 9 (10) ◽  
pp. 411 ◽  
Author(s):  
Shanhe Liu ◽  
Zhiwen Luo ◽  
Keer Zhang ◽  
Jian Hang
Keyword(s):  
Natural Ventilation ◽  
Recirculation Zone ◽  
Cfd Simulation ◽  
Flow Simulation ◽  
Small Scale ◽  
Road Tunnel ◽  
Velocity Reduction ◽  
Road Tunnels ◽  
Reduction Effect ◽  
Ventilation Performance

Providing efficient ventilation in road tunnels is essential to prevent severe air pollution exposure for both drivers and pedestrians in such enclosed spaces with heavy vehicle emissions. Longitudinal ventilation methods like commercial jet fans have been widely applied and confirmed to be effective for introducing external fresh air into road tunnels that are shorter than 3 km. However, operating tunnel jet fans is energy consuming. Therefore, for small-scale (~100 m–1 km) road tunnels, mechanical ventilation methods might be highly energetically expensive and unaffordable. Many studies have found that the use of wind catchers could improve buildings’ natural ventilation, but their effect on improving natural ventilation in small-scale road tunnels has, hitherto, rarely been studied. This paper, therefore, aims to quantify the influence of style and arrangement of one-sided flat-roof wind catchers on ventilation performance in a road tunnel. The concept of intake fraction (IF) is applied for ventilation and pollutant exposure assessment in the overall tunnel and for pedestrian regions. Computational fluid dynamics (CFD) methodology with a standard k-epsilon turbulence model is used to perform a three-dimensional (3D) turbulent flow simulation, and CFD results have been validated by wind-tunnel experiments for building cross ventilation. Results show that the introduction of wind catchers would significantly enhance wind speed at pedestrian level, but a negative velocity reduction effect and a near-catcher recirculation zone can also be found. A special downstream vortex extending along the downstream tunnel is found, helping remove the accumulated pollutants away from the low-level pedestrian sides. Both wind catcher style and arrangement would significantly influence the ventilation performance in the tunnel. Compared to long-catcher designs, short-catchers would be more effective for providing fresh air to pedestrian sides due to a weaker upstream velocity reduction effect and smaller near-catcher recirculation zone. In long-catcher cases, IF increases to 1.13 ppm when the wind catcher is positioned 240 m away from the tunnel entrance, which is almost twice that in short-catcher cases. For the effects of catcher arrangements, single, short-catcher, span-wise, shifting would not help dilute pollutants effectively. Generally, a design involving a double short-catcher in a parallel arrangement is the most recommended, with the smallest IF, i.e., 61% of that in the tunnel without wind catchers (0.36 ppm).

scholarly journals Group Layout Pattern and Outdoor Wind Environment of Enclosed Office Buildings in Hangzhou

Energies ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 406 ◽  
Author(s):  
Xiaoyu Ying ◽  
Yanling Wang ◽  
Wenzhe Li ◽  
Ziqiao Liu ◽  
Grace Ding
Keyword(s):  
Natural Ventilation ◽  
Cfd Simulation ◽  
Simulation Software ◽  
Office Building ◽  
Wind Environment ◽  
Site Model ◽  
Advantages And Disadvantages ◽  
Building Layout ◽  
Ventilation Performance ◽  
Group Layout

This paper presents a study of the effects of wind-induced airflow through the urban built layout pattern using statistical analysis. This study investigates the association between typically enclosed office building layout patterns and the wind environment. First of all, this study establishes an ideal site model of 200 m × 200 m and obtains four typical multi-story enclosed office building group layouts, namely the multi-yard parallel opening, the multi-yard returning shape opening, the overall courtyard parallel opening, and the overall courtyard returning shape opening. Then, the natural ventilation performance of different building morphologies is further evaluated via the computational fluid dynamics (CFD) simulation software Phoenics. This study compares wind speed distribution at an outdoor pedestrian height (1.5 m). Finally, the natural ventilation performance corresponding to the four layout forms is obtained, which showed that the outdoor wind environment of the multi-yard type is more comfortable than the overall courtyard type, and the degree of enclosure of the building group is related to the advantages and disadvantages of the outdoor wind environment. The quantitative relevance between building layout and wind environment is examined, according to which the results of an ameliorated layout proposal are presented and assessed by Phoenics. This research could provide a method to create a livable urban wind environment.

scholarly journals Optimization of Window Positions for Wind-Driven Natural Ventilation Performance

Energies ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2464
Author(s):  
Nari Yoon ◽  
Mary Ann Piette ◽  
Jung Min Han ◽  
Wentao Wu ◽  
Ali Malkawi
Keyword(s):  
Architectural Design ◽  
Natural Ventilation ◽  
Cfd Simulation ◽  
Design Decision ◽  
Building Facades ◽  
Window Position ◽  
Computational Fluid Dynamics Cfd ◽  
Ventilation Performance ◽  
Energy Simulations ◽  
The Impact

This paper optimizes opening positions on building facades to maximize the natural ventilation’s potential for ventilation and cooling purposes. The paper demonstrates how to apply computational fluid dynamics (CFD) simulation results to architectural design processes, and how the CFD-driven decisions impact ventilation and cooling: (1) background: A CFD helps predict the natural ventilation’s potential, the integration of CFD results into design decision-making has not been actively practiced; (2) methods: Pressure data on building facades were obtained from CFD simulations and mapped into the 3D modeling environment, which were then used to identify optimal positions of two openings of a zone. The effect of the selected opening positions was validated with building energy simulations; (3) results: The cross-comparison study of different window positions based on different geographical locations quantified the impact on natural ventilation effectiveness; and (4) conclusions: The optimized window position was shown to be effective, and some optimal solutions contradicted the typical cross-ventilation strategy.

Efficient Numerical Investigation of Ventilation System Design of Road Tunnels

2012 ◽  
Author(s):  
Dicken K. H. Wu ◽  
Y. F. Lin ◽  
Y. F. Pin ◽  
Dora W. S. Tsui
Keyword(s):  
Cfd Simulation ◽  
Ventilation System ◽  
Three Dimensional ◽  
Simulation Method ◽  
Road Tunnel ◽  
Piston Effect ◽  
The Road ◽  
Road Tunnels ◽  
Safety Consideration ◽  
Effective Ventilation

The road tunnel air quality would easily deteriorate if the vehicle-emitted exhaust gas is not properly removed or diluted. As a result, one of the major functions of effective ventilation in road tunnels is to prevent harmful substances from affecting tunnel users and also to maintain good visibility inside for safety consideration. In the present study, a highly efficient three-dimensional computational fluid dynamics (3D CFD) simulation method has been developed and tested to model the traffic induced piston effect in a full scale road tunnel. This method is useful for the design of tunnel ventilation systems.

scholarly journals Ventilation Characteristics and Performance Evaluation of Different Window-Opening Forms in a Typical Office Room

2021 ◽  
Vol 11 (19) ◽  
pp. 8966
Author(s):  
Yuanyuan Wang ◽  
Yanzhe Yu ◽  
Tianzhen Ye ◽  
Quan Bo
Keyword(s):  
Thermal Comfort ◽  
Natural Ventilation ◽  
Cfd Simulation ◽  
Thermal Sensation ◽  
Ventilation Rate ◽  
Window Opening ◽  
Ventilation Modes ◽  
Ventilation Performance ◽  
Scale Experiment ◽  
And Performance

As most existing office buildings in China lack fresh air systems for ventilation, natural ventilation with windows remains the main means of improving indoor air quality and adjusting indoor thermal comfort. However, knowledge of the ventilation characteristics of various window-opening forms in actual buildings is limited and current methods for evaluating ventilation performance lack a comprehensive consideration of ventilation rate and thermal comfort. In this study, the ventilation characteristics of different window-opening forms were systematically compared by conducting computational fluid dynamics (CFD) simulations. A full-scale experiment was conducted in a typical office room in a university in Tianjin to validate the CFD simulation. Two ventilation modes (wind-driven cross-ventilation and temperature-driven single-sided ventilation), three window-opening angles, and seven window types were investigated. Additionally, the ratio of the ventilation rate to the absolute value of thermal sensation was used to quantify the indoor natural-ventilation performance. The results showed that a sliding window with a full opening has the highest discharge coefficients of 0.68 and 0.52 under wind-driven cross-ventilation and temperature-driven single-sided ventilation, respectively, and top-hung windows opening both inwards and outwards have better ventilation performance than other window types under the two ventilation modes. This study is applicable to the design and practice of natural ventilation.

scholarly journals Study of the Smoke Propagation in a Road Tunnel

2013 ◽  
Vol 6 (1) ◽  
pp. 51-68
Author(s):  
B. Kalech ◽  
B. Jouini ◽  
M. Bouterra ◽  
A. El Cafsi ◽  
A. Belghith
Keyword(s):  
Urban Areas ◽  
Numerical Study ◽  
Heavy Traffic ◽  
Air Flow ◽  
Small Scale ◽  
Road Tunnel ◽  
Smoke Flow ◽  
Tunnel Fire ◽  
Road Tunnels ◽  
Fire Smoke

Road tunnels are increasingly built due to heavy traffic in dense urban areas. Knowledge of the spread of smoke is still limited. A numerical study on the smoke flow in a tunnel has been made using the model of small-scale tunnel. Effects of the longitudinal air flow on the flow structure, the temperature distribution and the smoke stratification of the fire in the tunnel have been considered by taking into account the inclination of the tunnel and the transverse positioning of the source. The results show that the spread of smoke is independent of the transverse position of the source in the fourth phase of the flow. The slope has a slight influence on the flow and promotes the flow stratification in a ascending slope. The longitudinal air flow promotes destratification of the smoke flow. The model was validated by comparison with experimental data obtained from fire tests (Wu et al.) in a small-scale tunnel.  Keywords: Tunnel fire; Smoke flow; Stratification; FDS  © 2014 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved.  doi: http://dx.doi.org/10.3329/jsr.v6i1.14696 J. Sci. Res. 6 (1), 51-68 (2014)

scholarly journals Ventilation performance and pollutant flow in a unidirectional-traffic road tunnel

2017 ◽  
Vol 21 (suppl. 3) ◽  
pp. 783-794 ◽  
Author(s):  
Milan Sekularac ◽  
Novica Jankovic ◽  
Petar Vukoslavcevic
Keyword(s):  
Velocity Distribution ◽  
Ventilation System ◽  
Numerical Approach ◽  
Temperature Fields ◽  
Laboratory Model ◽  
Road Tunnel ◽  
Tunnel Fire ◽  
Starting Point ◽  
Road Tunnels ◽  
Ventilation Performance

To develop a reliable method for modeling fire case scenarios within the road tunnels and observing the effects of the skewed velocity, experimental and numerical approach is used. Experimental results obtained from a laboratory tunnel model installation, are used to define geometry and boundary conditions. The result for the overall ventilation performance is compared to the available cases, for empty tunnel and stationary bi-directional vehicle traffic. For a unidirectional traffic road tunnel, in traffic loaded conditions, with a ventilation system based on axial ducted fans, the numerical simulation is used to determine the flow and temperature fields, the ventilation efficiency (efficiency of momentum transfer), and to assess the shape of the velocity distribution. The effect that a skewed velocity distribution can have on the resulting thermal and pollutant fields (CO2), smoke backlayering and stratification, is evaluated using numerical simulations, for the model-scale tunnel fire conditions. The effect of two possible limiting shapes of the velocity distribution, dependent only on the location of the fire with respect to the nearest upstream operating fans, is analyzed. The numerical results for a fire are scenario are a starting point in assessing the feasibility of a laboratory model fire-scenario experiment, what is planned as the next step in this research.

Impacts of opening baffle of city road tunnels on natural ventilation performance

2013 ◽  
Vol 7 (1) ◽  
pp. 55-61 ◽  
Author(s):  
Weixiao Yang ◽  
Jincheng Xing ◽  
Jianxing Li ◽  
Jihong Ling ◽  
Haixian Hao ◽  
...  
Keyword(s):  
Natural Ventilation ◽  
Road Tunnels ◽  
Ventilation Performance

scholarly journals Risk Analysis of Road Tunnels: A Computational Fluid Dynamic Model for Assessing the Effects of Natural Ventilation

2020 ◽  
Vol 11 (1) ◽  
pp. 32
Author(s):  
Ciro Caliendo ◽  
Gianluca Genovese ◽  
Isidoro Russo
Keyword(s):  
Natural Ventilation ◽  
Fluid Dynamic ◽  
Movement Time ◽  
Radiant Heat ◽  
Heat Fluxes ◽  
Maximum Heat ◽  
Road Tunnels ◽  
Maximum Heat Release ◽  
Computational Fluid Dynamics Cfd ◽  
Time Required

We have developed an appropriate Computational Fluid Dynamics (CFD) model for assessing the exposure to risk of tunnel users during their evacuation process in the event of fire. The effects on escaping users, which can be caused by fire from different types of vehicles located in various longitudinal positions within a one-way tunnel with natural ventilation only and length less than 1 km are shown. Simulated fires, in terms of maximum Heat Release Rate (HRR) are: 8, 30, 50, and 100 MW for two cars, a bus, and two types of Heavy Goods Vehicles (HGVs), respectively. With reference to environmental conditions (i.e., temperatures, radiant heat fluxes, visibility distances, and CO and CO2 concentrations) along the evacuation path, the results prove that these are always within the limits acceptable for user safety. The exposure to toxic gases and heat also confirms that the tunnel users can safely evacuate. The evacuation time was found to be higher when fire was related to the bus, which is due to a major pre-movement time required for leaving the vehicle. The findings show that mechanical ventilation is not necessary in the case of the tunnel investigated. It is to be emphasized that our modeling might represent a reference in investigating the effects of natural ventilation in tunnels.

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