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A Study on Diffusion Characteristics and Crossflow Mechanism of Pollutants at the Portals of Highway Tunnel Group
(1. College of Quality & Safety Engineering, China Jiliang University, Hangzhou 310018; 2. Center for Balance Architecture,Zhejiang University, Hangzhou 310007; 3. School of Management, Hunan University of Information Technology, Changsha 410151;4. School of Public Affairs, Zhejiang University, Hangzhou 310058; 5. School of Electronic Engineering, Xi'an Shiyou University,Xi′an 710065; 6. Engineering Research Center of Oceanic Sensing Technology and Equipment under Ministry of Education,Zhejiang University, Zhoushan 316021; 7. Zhejiang University Zhongyuan Institute, Zhengzhou 450000)
Abstract With the increase in highway tunnel groups with multiple tunnel portals in close proximity, there has been a more and more prominent problem of pollutants gathering and cross-impact between tunnel portals. However, parameters in extant studies are of a narrow range and there is a lack of systematic analyses of the crossflow mechanism of tunnel pollutants. The study uses CFD simulation and scale model test to investigate the process of pollutant diffusion at the portals of highway tunnel group, and analyzes the flow field characteristics of pollutant diffusion and the changing pattern of crossflow ratio at the tunnel portals with 20~320 m spacing. The impact range of upstream jet and downstream suction are also taken into account, a pollutant crossflow model is constructed, and an empirical formula of crossflow ratio is obtained applicable for engineering calculation. The results show that: (1) The diffusion of tunnel pollutants is affected by the joint action of jet development at the upstream tunnel portal and suction at the downstream tunnel. The diffusion of upstream tunnel pollutants is in line with the 3D wall jet theory, and the wind speed, expansion range, and decay rate of pollutant concentration of each section at the portal section are similar and satisfy the standard for similarity in terms of distribution. The length of the downstream convergence section is short and the suction does not change the morphology of the upstream jet. (2) The crossflow of tunnel pollutants is affected by the joint action of the structural parameter L/D (tunnel portal spacing/tunnel hydraulic diameter) and the operational parameter vup/vdown (upstream and downstream wind speed ratio), both of which act independently of each other on the crossflow. As L/D increases, the crossflow ratio φs and the crossflow concentration ratio φc decrease together. When vup/vdown increases, φs first stays constant before decreasing gradually, while φc first increases before stabilizing. This pattern is not affected by the form of the tunnel section. (3) The empirical formula the study constructs for the crossflow ratio is in line with extant studies and has a wider scope of application.
Abstract：
With the increase in highway tunnel groups with multiple tunnel portals in close proximity, there has been a more and more prominent problem of pollutants gathering and cross-impact between tunnel portals. However, parameters in extant studies are of a narrow range and there is a lack of systematic analyses of the crossflow mechanism of tunnel pollutants. The study uses CFD simulation and scale model test to investigate the process of pollutant diffusion at the portals of highway tunnel group, and analyzes the flow field characteristics of pollutant diffusion and the changing pattern of crossflow ratio at the tunnel portals with 20~320 m spacing. The impact range of upstream jet and downstream suction are also taken into account, a pollutant crossflow model is constructed, and an empirical formula of crossflow ratio is obtained applicable for engineering calculation. The results show that: (1) The diffusion of tunnel pollutants is affected by the joint action of jet development at the upstream tunnel portal and suction at the downstream tunnel. The diffusion of upstream tunnel pollutants is in line with the 3D wall jet theory, and the wind speed, expansion range, and decay rate of pollutant concentration of each section at the portal section are similar and satisfy the standard for similarity in terms of distribution. The length of the downstream convergence section is short and the suction does not change the morphology of the upstream jet. (2) The crossflow of tunnel pollutants is affected by the joint action of the structural parameter L/D (tunnel portal spacing/tunnel hydraulic diameter) and the operational parameter vup/vdown (upstream and downstream wind speed ratio), both of which act independently of each other on the crossflow. As L/D increases, the crossflow ratio φs and the crossflow concentration ratio φc decrease together. When vup/vdown increases, φs first stays constant before decreasing gradually, while φc first increases before stabilizing. This pattern is not affected by the form of the tunnel section. (3) The empirical formula the study constructs for the crossflow ratio is in line with extant studies and has a wider scope of application.
ZHU Kai1,
2 YANG Wenjing1 ZHANG Qionghua3 LIU Bin4 WANG Qiang1 ZHANG Xin5 WU Ke2,
6 etc
.A Study on Diffusion Characteristics and Crossflow Mechanism of Pollutants at the Portals of Highway Tunnel Group[J] MODERN TUNNELLING TECHNOLOGY, 2023,V60(2): 212-222
2023, Vol. 60 