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Jin S.,Nanjing University of Technology | Jin S.,Jilin Institute of Architecture and Civil Engineering | Gong Y.,Nanjing University of Technology | Gong Y.,Green Building Research Center
Resources, Environment and Engineering - Proceedings of the 2014 Technical Congress on Resources, Environment and Engineering, CREE 2014 | Year: 2015

Airflow in the urban canopy space is the sub-flow driven by the upper flow. There will be three types of flow in street canyon depending on the canyon structure. An evolutional model was presented to illustrate the development of airflow in street canyon. The model was established based on the length model of wind shadow according to the results of 79 groups of simulation experiments. The results show that: When the width of the street canyon was larger than the length of wind shadow, wind fields of the two buildings were independent of each other. When the inner space of street canyon was in the wind shadow area, a stable vortex circulation was formed, which was independent of upper flow. In addition, bottom-up flow near the leeward side of the former building was its significant characteristic in wake turbulence. Source


Jin S.,Nanjing University of Technology | Jin S.,Green Building Research Center | Gong Y.,Nanjing University of Technology | Gong Y.,Green Building Research Center
2011 International Conference on Electric Technology and Civil Engineering, ICETCE 2011 - Proceedings | Year: 2011

The accuracy and the applicability of LK model in the field of urban wind simulation, which fixes the structural defects of the standard k model, are further verified. Also, the paper analyzes the impacts of the spatial structure of urban canopy on the regional wind circumstance, and proposes fitting formula of relative region wind speed, building coverage ratio and building space ratio, based on the wind analysis of Sanpailou area in Nanjing under the typical summer wind speed. Besides, the paper explores the exhibition of the wind condition in different city configurations and different types of architecture. From the perspective of the city, the paper explores the connection between the wind circumstance and the spatial structure of urban canopy, which including the architectural composition and building space forms. © 2011 IEEE. Source


Sike J.,Nanjing University of Technology | Sike J.,Jilin Institute of Architecture and Civil Engineering | Yanfeng G.,Nanjing University of Technology | Yanfeng G.,Green Building Research Center | Guangli Z.,Nanjing University of Technology
Journal of Wind Engineering and Industrial Aerodynamics | Year: 2015

Shallow-buried road tunnel with roof openings is a green energy-saving technology. In this kind of tunnel, natural ventilation and natural smoke extraction can be realized through the roof openings. Now there are four shallow-buried road tunnels in Nanjing. Since operation, this kind of tunnel has been widely praised for the high air quality inside tunnel, but there is yet no regular design method of it. Buried section is the basic unit of this type of tunnel, while fully understanding of the development of flow field and velocity distribution is the foundation of solving the above problem. Based on simplified flow filed in the buried section and Prandtl velocity distribution law, this paper presented the formula of velocity distribution in the buried section. Besides, a 1/10 reduced-scale tunnel experiment platform was built to test the tunnel flow field on 9 kinds of traffic conditions. Energy transfer and dissipation law in the tunnel flow field were explained based on the concept of energy gradient and the formula of velocity distribution. Research showed that the velocity of the flow field increases quickly and then becomes stable with unidirectional uniform traffic. Velocity meets the logarithmic relationship with height. The air velocity in the tunnel varies approximately linearly with the vehicle speed. And the vehicle speed has much more influence on air velocity than the vehicle spacing. The energy transferred to the airflow from vehicles evolved into two parts in the flow field. One part is absorbed by the flow field and converted into the kinetic energy of the flow field itself. The other part is dissipated in turbulence. The kinetic energy increment increases with the height of the tunnel. The dissipation of energy along the tunnel presents an asymmetrical U-shaped distribution. When the flow becomes stable, the dissipation of energy also becomes stable, and the kinetic energy increment approaches zero. © 2015 Elsevier Ltd. Source

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