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Journal of Zhejiang University SCIENCE A 1998 Vol.-1 No.-1 P.

http://doi.org/10.1631/jzus.A2400405


Flow loss characteristics in parallel confluence sections of tunnels


Author(s):  Xin ZHANG, Hao HE, Xiaofeng CHEN, Yachao LI, Tianhang ZHANG, Yuehui WANG, Kai ZHU, Ke WU

Affiliation(s):  College of Electronic Engineering, Xi'an Shiyou University, Xi'an 710065, China; more

Corresponding email(s):   tianhang.zhang@connect.polyu.hk, wuke@zju.edu.cn

Key Words:  Parallel bifurcated tunnel, Convergence ratio, Flow characteristics, Loss coefficients


Xin ZHANG, Hao HE, Xiaofeng CHEN, Yachao LI, Tianhang ZHANG, Yuehui WANG, Kai ZHU, Ke WU. Flow loss characteristics in parallel confluence sections of tunnels[J]. Journal of Zhejiang University Science A, 1998, -1(-1): .

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author="Xin ZHANG, Hao HE, Xiaofeng CHEN, Yachao LI, Tianhang ZHANG, Yuehui WANG, Kai ZHU, Ke WU",
journal="Journal of Zhejiang University Science A",
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number="-1",
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publisher="Zhejiang University Press & Springer",
doi="10.1631/jzus.A2400405"
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%T Flow loss characteristics in parallel confluence sections of tunnels
%A Xin ZHANG
%A Hao HE
%A Xiaofeng CHEN
%A Yachao LI
%A Tianhang ZHANG
%A Yuehui WANG
%A Kai ZHU
%A Ke WU
%J Journal of Zhejiang University SCIENCE A
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%@ 1673-565X
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%I Zhejiang University Press & Springer
%DOI 10.1631/jzus.A2400405

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T1 - Flow loss characteristics in parallel confluence sections of tunnels
A1 - Xin ZHANG
A1 - Hao HE
A1 - Xiaofeng CHEN
A1 - Yachao LI
A1 - Tianhang ZHANG
A1 - Yuehui WANG
A1 - Kai ZHU
A1 - Ke WU
J0 - Journal of Zhejiang University Science A
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EP -
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Y1 - 1998
PB - Zhejiang University Press & Springer
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DOI - 10.1631/jzus.A2400405


Abstract: 
The construction of bifurcated tunnels is essential to advancing urban infrastructure systems, as they conserve land, reduce carbon emissions, and optimize traffic. However, the bifurcation structure of the parallel confluence section of such tunnels poses significant challenges in the design and operation of the tunnel ventilation system, in terms of both the internal and external environment. In this work, the flow and loss characteristics of parallel confluence sections is studied with numerical simulations and model experiments. The influence of the confluence ratio q and the confluence angle θ on the flow characteristics and loss mechanisms of the parallel confluence section are revealed theoretically. The results indicate that when q is small, the high-velocity airflow from the mainline entrains the low-speed airflow from the ramp, leading to flow separation at the upper connection between the parallel section and the gradual transition section; when q is large, the high-velocity airflow from the ramp entrains the low-speed airflow from the mainline, resulting in flow separation on the side of the confluence section adjacent to the mainline. Additionally, the mismatch between the airflow ratio Q and area ratio φ of the mainline tunnel and the ramp prior to confluence enhances the jet entrainment effect, increases the curvature of the streamline, expands the range of the flow separation area, and generates higher confluence loss coefficients |K13| and |K23| of the mainline and the ramp. For small q, K13 and K23 remain relatively constant with respect to θ, whereas for large q, both |K13| and |K23| decrease as θ increases. Finally, a semi-empirical formula is proposed to predict the loss coefficients for parallel bifurcated tunnels with confluence angles ranging from 5° to 15°. This study provides insights into the aerodynamic behaviour and loss mechanisms in bifurcated tunnels, offering guidelines for enhancing the efficiency of tunnel ventilation systems in tunnel-like underground infrastructure.

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