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ScienceDirect Procedia
Engineering
ELSEVIER Procedia Engineering 169 (2016) 340 - 349
www.elsevier.com/locate/procedia
4th International Conference on Countermeasures to Urban Heat Island (UHI) 2016
Study on the Application of Ventilation Corridor Planning in Urban
New Area
--A Case Study of Xixian New Area
Na Sua,b*, Dian Zhoua, Xiaotao Jianga
a Xi'an Jiaotong University, 28 West Xianning Road, Beilin District, Xi'an, 710049 _bXi'an city planning and Design Institute, 178 LaoDong Road, Lianhu District, Xi'an, 710082_
Abstract
The cause of urban heat island effect is closely related to urban activities, urban construction environment and landscape. The planning of urban ventilation corridor in Urban New District focuses on the optimization of the wind environment, not only can effectively improve the quality of living environment, but also can conducive to the realization of energy-saving emission reduction.
According to the urban wind air flow movement and urban underlying surface characteristics, the paper takes Xixian New Area as an example, according to the climate in cold regions divided different ecological and climatic zoning, uses CFD simulation method, and determines the city through the main control factors of the location and number of wind corridor, purporting and corridor on the windward side of density control in urban ecology and open space layout, in order to providing a reference for future planning and construction has a good climate and environment in new city. © 2016 The Authors.PublishedbyElsevierLtd. Thisis an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Peer-review under responsibility of the organizing committee of the 4th IC2UHI2016 Keywords: Urban New Area; Ventilation Corridor; Planning Method Application; XiXian New Area
1. Introduction
The studies of method of combining theoretical analysis with simulation analysis, carries on the system analysis to the cold region city district summer urban wind environment, to find out the effect the wind environment of geographical and climate, building environment and architectural form factors. According to the consideration factors of the index system of urban new district control planning stage, the index system of Urban Ventilation corridor control is discussed.
* Corresponding author. Tel.: +86-13759909496; E-mail address: sunagood@126.com
CrossMarl
1877-7058 © 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Peer-review under responsibility of the organizing committee of the 4th IC2UHI2016 doi: 10.1016/j.proeng.2016.10.042
Rapid urbanization process, the urban activity intensifies, bring urban haze, urban heat island urban climate phenomena, the living environment of the city and comfort effect, change the urban scale and mesoscale flow field structure, thereby affecting the transformation of air pollution and conveying process [1].
2. Methods
2.1. Urban Heat Island and urban ventilation
Urban heat island refers to when the urban development to a certain scale, due to the urban nature of the pad surface changes, atmospheric pollution and artificial waste heat emissions the city temperature was higher than that in suburban [2], causing air rises in the city, sank in the suburbs, air in the suburbs to the urban area of low pressure filling, forming urban heat island circulation phenomenon. In the circulation of urban heat island, the underlying surface condition of the city determines the characteristics of the urban atmospheric physical environment, see Fig. 1.
Fig. 1. Section analysis of typical urban heat island.
The cause of urban heat island effect is closely related to urban activities, urban construction environment and landscape, and the positive correlation between the urban heat island effect and urban population size and wind speed is very obvious.
Urban ventilation corridor, is the use of wind characteristics, from the ventilation system, under the effect of wind pressure, the city suburb of fresh air into the city, urban carbon oxygen balance, adjust the microclimate. According to the German Kress professor in accordance with the laws of local circulation operation proposed underlying surface climate function evaluation standard, and the underlying surface points for function space, compensation space and the air guide channel [3].
Urban new district plays an important role in the development of the city, and it is also a typical representative of the quality and level of the new urbanization construction. Urbanization increases the occurrence of urban heat island, and under the action of large scale wind field, the temperature of the City suburb also rises obviously. In the planning of Urban New District, the optimization of the wind environment can effectively improve the quality of living environment, but also conducive to the realization of energy saving and emission reduction. Under the guidance of urban space, change the urban architectural environment, increase urban green space, urban wind speed regulation, prompting the local flow field changes [4,5] which helped to improve the local micro meteorological conditions and atmospheric physical environment.
2.2. City open space and ventilation corridor
Urban green space, water is the important urban open space and time [6,7] combined with green space system planning, according to the principle of oxygen balance, the use of wind rose diagram magnification method,
different types of urban green suburb oxygen source estimation [8],the urban air passage and concentrated green land layout principle proposed urban ventilation corridor width should be inversely proportional to the average annual wind speed, and ventilation is proportional to the area .
The increase of natural surface water and green space in urban area [9], there are conducive to urban reduction temperature, increase humidity, change of local flow field, which helped to improve the local micro meteorological conditions and atmospheric physical environment. Increase the area of urban water, increase the capacity of urban air mixing and diffusion. With the increase of urban water area, the average wind speed in the urban area increases [10,15]. And the numerical simulation results show that the distribution of the dispersed water body is more significant to the micro meteorological environment in the urban area.
3. Research Framework
3.1. Research area
Xixian New Area is located in the west of Xi'an urban area, Xianyang City East. It is in the east of Xi'an Sanqiao and in the south of Huxian and Chang'an and Weihe River is in the north.
Xixian New Area is the 7th National District, in accordance with the development orientation of modern garden city, is an important node in the Silk Road Economic Belt and Guanzhong Urban Group ecology and climate environment regulation spatial planning demonstration base [17]. Relying on natural and human resources, the planning area is based on the water system, the site corridor and the road traffic as the skeleton. According to the requirements of the overall urban planning, the region will be built as a "core plate support, fast traffic connection, beautiful small town, urban agriculture," the ecological garden city.
Throughout the planning and control of the total area of 882 km2, construction land 272 km2. Xixian New Area belongs to the Guanzhong Basin and Weibei plateau region, terrain from the northwest and southeast to the Fenghe River reduced, central Fenghe river valley plain, mountain and plain is scattered distribution. The winter wind in the West salty area is the highest frequency wind direction, which is 2.2 m/s, the mean wind speed is, the wind direction is southwest, and the mean wind speed is 1.7 m/s. According to the above climate data, to accurately simulate the urban air duct, the effective use of the summer monsoon of urban natural ventilation, avoid winter monsoon of urban amenity, using computational fluid dynamics software CFD simulated climatic conditions are as follows: northeast wind in summer, the average wind speed of 2 m /s.
3.2. Research ideas
The ventilation channel planning scheme is based on the digital analysis of meteorological conditions, urban ecosystem, urban heat island mitigation and the comprehensive consideration of urban energy saving. Depression within the scope of the planning through the analysis in the investigation of the area surrounding the lake and river water, water quality, large sites and biological conditions found: Fenghe River from the regional center, the river flows north into the Weihe River. It ordinate from the Qinling Fengyukou , around the basin of the biological diversity is rich, which makes it become urban ecological corridor ; Secondly, Xixian New Area is in the northeast side of the Weihe River, Jing River and other natural water around, which means that in the summer the dominant wind direction wind can form ideal cold air corridor across the region; Last but not the least, the status in Xixian New Area have numbers of ponds and ditches for generalizing ventilation road
In addition, it can also be found through the digital analysis of the weather in the area and the simulation of the computer city wind field:
First, if we take Fengdong new city center area for example, distributed and massive closed type water and green, if there is no air duct with, would alleviate the urban heat island effect and improve the urban micro climate [11] and no much positive impact; thermal conditions, summer water can absorb and store a lot of heat, summer water surrounding lots of air humidity increases, water vapor exchange effect to the surrounding land [12].
In addition, Kunming basin area by the natural water, green and open space corridor and low density development zone composed of Urban Ventilation plaque exactly in line with the requirements. The ideal solution should be a relatively low air temperature, a certain wind speed and the correct direction of the wind.
4. Construction of Urban Ventilation Corridor-A Case Study of Xixian New Area
4.1. Division of eco-climate control area, protection oof compensation space
First on the current situation of the development of the city of specific analysis, of structure of ventilation system for a clear division, the air supply to the system to understand, according to different climate and environment, determine the main elements, in space, space compensation and Urban Ventilation corridors three different spatial attributes, take different planning control principle. (Fig. 2)
Space compensation mainly refers to the cold air generation region, including grassland, arable land, mountain forest, due to the different surface heat, night in these areas near ground air cooling degree is different, cold air sinks, easy to form cold air generation zone.
Urban Ventilation corridors planning should give full play to the urban green space and water system of cold source of urban function and in Xixian new area of Weihe River, Fenghe River and other rivers as the main ventilation corridor, guiding the flow of air.
Main elements of ventilati on corridor in Xixian New Area | Main factors Present situation Development goals I
Cold air generating area _ Forest, grassland, water, farmland Have a ready pen, blending the Garden Citv
Function space Urban and rural areas Urban agriculture, modern service industry
Ventilation corridor rivers, green spaces exist, ecological base To protect, coordinate with urban development
Urban Ventilation corridor planning modern agricultural culture, the modern city culture
Fig. 2. Analysis of the components of the ventilation corridor in Xixian New Area
4.2. Application of CFD to regional wind environment simulation
Based on computational fluid dynamics CFD [13] computer urban wind field simulation can simulate the regional wind environment (Fig. 3).
Fig. 3: (a) Fengdong New city 1-meter-high wind speed simulation map
Fig. 3: (b) Fengdong New city 10-meter-high wind speed simulation map
(1) Urban wind speed by surrounding buildings layout, city underlying surface hinder [14], due to the effect of surface roughness on the ground level air flow, surface rough degree with the friction was proportional to the, with the same wind speed is inversely proportional, that is, the greater the friction, the greater the influence of wind speed. More to the central area, the building floor area ratio is bigger, the construction is denser [16]. The wind speed is smaller, more to the suburbs, the construction intensity is smaller, and the wind speed is bigger.
(2) Urban wind speed by the height from the ground effect, the higher the distance from the ground, the greater the wind speed, under the influence of underlying surface on smaller and smaller.
(3) City ventilation path planning, combined with a wide range of urban landscape planning, especially adapt to urban dominant wind direction are arranged, the urban green corridor and the surrounding natural environment effective through and reduce the other factors of the corridor ventilation intervention.
In different cities, because of the different land use types, construction intensity is different, different floor area ratio, building density and other indicators, wind speed is also different. Generally speaking, the wind speed is in inverse proportion to the volume ratio and the building density, that is, the greater the volume ratio and the building density, the smaller the wind speed.
4.3. Urban ventilation corridor width analysis
The local circulation of the valley and the water surface is obvious in the whole year in the West and the East, and the local circulation in the valley and the water surface is obvious, so this paper only analyzes the ventilation corridor of the new city in the northeast wind direction and the southwest wind direction.
Based on the principle of urban air passage and green space centralized distribution, this paper puts forward that the width of Urban Ventilation corridor should be in inverse proportion to the average annual wind speed, and is proportional to the ventilation area. The ventilation rate of the design should be guaranteed within one day of the regional oxygen balance [9]. Set the city side length L (km), wind speed (km / h) V, city daily ventilation frequency T, air inlet channel of width W accounted for the proportion of the length of a side of the city is inverse of t. Namely /T W/L=1, W=L/T; among them, T=24V/L, W= (L1 * L2) /24V. In short, the construction of urban ventilation corridor is beneficial to increase the speed of the air circulation between the city and nature, and reduce the exchange cycle.
Planning combined with the road, water area, green land and open space, urban edge according to 20 km, annual average wind speed is 2 m/s (7.2 km/h, the average number of ventilation t for 864). The total width of the ventilation corridor required by the city is calculated as 3.65 km. According to the main channel 500-800 meters, probably need 4-5. Through the software simulation of wind environment, it can be seen that the greater the width of the wind tunnel, the smaller the wind speed is, the smaller the angle between the wind and the wind, the greater the wind speed (Fig. 4). In addition, focus on the construction of area of wind speed, wind speed with open space.
Fig. 4. Ventilation corridor in Xixian New Area
(1) Corridor A: Qin and Han new town site gallery is composed of a series of tombs, which is the longest ventilation corridor in the planning area. Because of the wind into the corridor at the site of the mausoleum is located within the area of open space, the shortest path to higher frequency accounted for 90%. That is to say, the friction resistance on the corridor is also the smallest.
(2) Corridor B: this corridor along the Weihe River, the water surface area is larger, the wind speed is affected by the local circulation, and the shortest path frequency is also higher.
(3) Corridor C: this corridor through Fengdong new town and Fengxi new city core area, passing through the business district, residential areas, mixed commercial and residential area construction intensive areas, because here including the Feng Dong and Fengxi the downtown lots, the corridor planning control has the greatest difficulty. The shortest path on the corridor is only about 10%, which is the lowest of the four corridors.
(4) Corridor D: this corridor through the city's four major site area, combined with Zhou, Qin, Han and Tang Dynasties site protection, construction quantity is small, just situation ruins park is gradually building, corridor capacity gradually strengthening.
The Fenghe River, Weihe River main ventilation corridor, the minimum width control for 150 meters; Haojing - Epang ventilated corridor, the minimum width control for 80 meters. The total area of the control area of the wind corridor is 10 km2, which accounts for 6% of the total planned area (Table 1). Using wind environment simulation software, the wind speed in the wind tunnel is increased by 0.5-1 m/s. The wind speed in the wind tunnel is mainly related to the width and the direction of the wind tunnel.
In order to improve the city micro circulation, purify the air quality, provide the residents with more favorable environment and recreation space, combined with the Kunming Water Conservancy Scenic Area and other city parks, the formation of "green spot", improve the urban ecological environment. At the same time to give full play
to the ecological benefits and social benefits of large sites park, green park and country park, to provide shelter for urban disaster prevention.
Table 1. List of main elements of urban ventilation corridors
Number Name Control Control Range Control Width Main Function
Element
1 Haojing Site Green wedge Determine the scope of the site protection plan 0.5- -4 km City Ventilation Main
2 Epang Palace Site Green wedge Determine the scope of the site protection plan 0.5- -4 km City Ventilation Main
3 Jianzhang Palace Site Green wedge Determine the scope of the site protection plan 0.5- -4 km City Ventilation Main
4 Fenghe River The green corridor Determine the scope of the River Protection Ordinance 0.5- -2 km City Ventilation Main
5 Weihe River The green corridor Determine the scope of the River Protection Ordinance 0.5- -2 km City Ventilation Main
4.4. Open space corridor control
The open space corridor. For the Urban Ventilation corridors, open space and width are equally important, often open space by building size determined, so deal with corridor construction land planning. Considering to the urban underlying surface, the planning should be in the main ventilation corridor set aside a large area of open space, important to roads, squares, green belt, construction land proportion shall not exceed 20%, building to low layer low density. Secondly, to form the overall urban air cycle system, to play the value of the various components of the node space.
Kunming Lake Basin, the location of the Doumen reservoir, located in the southwest of Changan, is the most famous lake in the Han Dynasty. Kunming basin is located in Xixian New Area site ventilation corridor, planning a total area of 10.4 square kilometers, with a total capacity of 46 million cubic meters, in accordance with the internal and external Lake layout. The Neihu for urban water supply, storage lead Han JiWei trunk runoff; the detention basin, Lake City water supply protection, improve Fenghe ecological environment.
Another value of the planning of the Kunming pool area is to balance the regional ecological environment and regulate the micro climate. A huge green space as the core, for the surrounding ecological regulation and the impact of the climate is self-evident. Kunming pool around the country park, agriculture ecological garden layout contains the Han Stone whale Forest Park and gratitude pool Forest Park, making a garden district, a district view, patchwork background, proper arrangement of low layer building (Fig. 5).
Fig. 5. (a) Kunming pool elevation simulation
Fig. 5. (b) Kunming pool open space control
4.5. Adjacent interface control
The control of the index is mainly aimed at the buildings on both sides of the corridor. The use of the construction of the wind density, that is, through the construction of the prevailing wind direction in the normal direction of the total construction area of the total construction area of the number, to control the adjacent interface (Table 2).
Table 2. Ventilation level of the control of the density of the wind
Ventilation grade Grading standard Ventilation efficiency
First stage ventilation Upwind surface densityX<30% excellent
Second stage ventilation Upwind surface density30%<X<70% common
Third stage ventilation Upwind surface densityl>70% Poor
The high proportion of the building and the strict requirement of the opening, so as to ensure the ventilation efficiency of the corridor. Because of the difference of the primary and the secondary ventilation corridor ventilation standard, control of the adjacent interface is diverse, the city's main ventilation corridor adjacent building height to width ratio should be strictly controlled at 0.5, the degree of openness to above 40%; and Urban Ventilation corridor, the height to width ratio also open degree reduce. (Fig. 6)
course_ ffaterfront green space>200M , Control area (500-200011)
Fig. 6. Height of the river around the building control schematic
5. Conclusion
At present, China's urban construction on the ecological environment impact of increasingly prominent, urban heat island and the urban poor ventilation have certain relationship. Therefore, the Urban Ventilation corridors planning, improve the urban wind environment and atmospheric environment is very necessary. In Xi xian new area planning practice to explore the Urban Ventilation corridor planning theory and method, put forward the Urban Ventilation corridors of the location, quantity and the open space planning control requirements.
However, there are still many places to improve on the study of Urban Ventilation corridor. For example, how to evaluate the ventilation efficiency of the air corridor, and how to improve the wind environment in the area outside the wind corridor are worth discussing and studying.
Thanks to the "eco - climate monitoring of the Guanzhong Urban Agglomeration space planning management and control technology and demonstration research" participation in the strong support.
Acknowledgements
This research was supported by the national science and technology support program project (2012BAJ15B06) & (2013FY112500).
References
[1] HJS Fernando, SM Lee, J Anderson et al. (2001).Urban Fluid Mechanics: Air Circulation and Contaminant Dispersion in Cities.
Environmental Fluid Mechanics , 107-164
[2] Zhou Shuzhen. (1994).City Climate [M.] Meteorological Press city climate,244-246
[3] Ren Chao Yuan Chao. (2014).A Study of Air Path and Its Application in Urban Planning [J]. Urban Planning Forum,216( 3), 52-59
[4] Tian Guo Xing, Jun Min Xing, Zhu Hongmei. (2009).Urban green space system planning research review and prospect [J]. Journal of
Northwest Forestry University, 24(3), 199-204.
[5] Huo Fei,Chen haishan. (2001).Numerial Simulation of the Effect of Large-Scale Wind on Urban Heat Island[J].Climatic and Environmental
Research,16(6),679-689
[6] Liu Shuyu, ShenJihuang et al. (2010) Urban ventilation channel planning method based on local circulations case study of
Stuttgart,Germany [J]. Journal of Zhejiang University, 44 (3),1985-1988
[7] Yang XueCheng Linyun et al. (2003) Practice of basic ecological principles of urban open space - Jiangmen City Urban Green Space
System Planning [J]. Chinese Landscape Architecture, 19 (3),69-72
[8] Wang Shaozeng Li Min. (2001) The open space of city ecological planning mechanism of [J]. Chinese Landscape Architecture, 17(5),32-35
[9] Xuan Chun Yi, Wang Xiaoyun et al. (2010)The effect of the layout of the urban water body on the atmospheric environment [J],
meteorology, 36 (12),94-101
[10] Wang Guangtao Wang Xiaoyun et al. (2005) Theory and method of modern urban planning a practice enlightenment [J]. Urban Planning
Forum, 160(6),18-22
[11] ZhongZhon, Zhang Yaocun. (2008).Meteorological effect of artificial water body and the change of local environment [M]. Science
Press ,24-35
[12] Xi Hongzheng Jiao Sheng et al.(2010) .Research on the Model of Creating Urban Natural Ventilation Channel for the Areas where It's Hot
in Summer and Cool in Winter[J].Huazhong architecture,28(6),p106-107
[13] A.Mochida,S.Murakami, et al.(1997).CFD analysis of mesoscale climate in the Greater Tokyo area, Journal of Wind Engineering and
Industrial Aerodynamics[J], 67&68,459-477
[14] G. Z. Brown and Mark DeKey. (2006).Sun,Wind&Light: Architectural Design Strategies[M].China Architecture & Building Press, 86-89
[15] Wang Guangtao, Wang Xiaoyun et al. (2005).Research and application of [J], Chinese science, 35(z1),145-155
[16] Zhao Hongbin Liu Hui. (2014) .Research onthe Methods of Building Ventilation Corridors among Basin Cities-- Taking the City of Xi'an as
theExample [J]. Chinese Landscape Architecture, 30(11), 32-35
[17] Planning of Xixian New Area (2010-2020),20-30
