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Scaling properties of Navier-Stokes turbulence

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第3期10卷 392-397页

作者： Zhao-cun LIU school of Environment and planning Henan University Kaifeng 475001 China

The property of the velocity field and the cascade process of the fluid flow are key problems in turbulence research. This study presents the scaling property of the turbulent velocity field and a mathematical description of the cascade process, using the following methods: (1) a discussion of the general self-similarity and scaling invariance of fluid flow from the viewpoint of the physical mechanism of turbulent flow; (2) the development of the relationship between the scaling indices and the key parameters of the She and Leveque (SL) model in the inertial range; (3) an investigation of the basis of the fractal model and the multi-fractal model of turbulence; (4) a demonstration of the physical meaning of the flowing field scaling that is related to the real flowing vortex. The results illustrate that the SL model could be regarded as an approximate mathematical solution of Navier-Stokes (N-S) equations, and that the phenomena of normal scaling and anomalous scaling is the result of the mutual interactions among the physical factors of nonlinearity, dissipation, and dispersion. Finally, a simple turbulent movement conceptional description model is developed to show the local properties and the instantaneous properties of turbulence.

关键词： Transformation equations Scaling Spiral structure Cascade Turbulence

Spatial Analysis of Commuting Mode Choice in Guangzhou, China

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Chinese Geographical Science 2013年第3期23卷 353-364页

作者： ZHOU Suhong DENG Lifang HUANG Meiyu school of Geography and planning Sun Yat-sen University Guangdong Key Laboratory for Urbanization and Geo-simulation Guangzhou Panyu Urban planning & Design Institute Bartlett school of planning University College London

Metropolitan cities in China are commonly confronted with unresolved traffic congestion issues, primarily due to rapidly increasing traffic demand. Group disparity between commuting mode choice and its spatial distribution on road networks has enabled us to examine the factors that give rise to the discrepancies and the fundamental spatial causes of traffic congestion. In recent years, mi- cro-perspective, individual, and behavior-based spatial analysis have mushroomed and been facilitated with effective tools such as tem- poral geographic information systems （T-GIS）. It is difficult to study the interrelations between transport and space on the basis of commuting mode choice since the mode choice data are invisible in a specific space such as a particular road network. Therefore, in the field of transport, the classical origin destination （OD） four-stage model （FSM） is usually employed to calculate data when studying commuting mode choice. Based on the relative principles of T-GIS and the platform of ArcGIS, this paper considers Guangzhou as a case study and develops a spatio-temporal tool to examine the daily activities of residents. Meanwhile, the traffic volume distribution in rush hours, which was analyzed according to commuting modes and how they were reflected in the road network, was scrutinized with data extracted from travel diaries. Moreover, efforts were made to explain the relationship between traffic demand and urban spatial structure. Based on the investigation, this research indicates that traffic volumes in divergent groups and on the road networks is driven by： l） the socio-economie characteristics of travelers; 2） a jobs-housing imbalance under suburbanization; 3） differences in the spatial supply of transport modes; 4） the remains of the Danwei （work unit） system and market development in China; and 5） the transition of urban spatial structure and other factors.

关键词： transport travel mode China temporal geographic information systems (T-GIS)

A novel unsupervised deep learning method for the generalization of urban form

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Geo-Spatial Information Science 2022年第4期25卷 568-587页

作者： Jihong Cai Yimin Chen school of Geography and planning Sun Yat-sen UniversityGuangzhouChina

Accurate delineation of urban form is essential to understand the impacts that urbanization has on the environment and regional *** supervised classification of urban form requires a rigidly defined scheme and high-quality sample data with class *** to the complexity of urban systems,it is challenging to consistently define urban form types and collect metadata to describe ***,in this study,we propose a novel unsupervised deep learning method for urban form delineation while avoiding the limitations of conventional super-vised urban form classification *** novelty of the proposed method is the Multiscale Residual Convolutional Autoencoder(MRCAE),which can learn the latent representation of differ-ent urban form *** vectors can be further used to generalize urban form types by using Self-Organizing Map(SOM)and the Gaussian Mixture Model(GMM).The proposed method is applied in the metropolitan area of Guangzhou-Foshan,*** MRCAE model along with SOM and GMM is used to generalize the urban form types from satellite *** physical and functional properties of each urban form type are also analyzed using several auxiliary datasets,including building footprints,Points-of-Interests(POIs)and Tencent User Density(TUD)*** results reveal that the urban form map generated based on the MRCAE can explain 55%of the building height distribution and 55%of the building area distribution,which are 2.1%and 3.3%higher than those derived from the conventional convolutional *** the information of urban form is essential to urban climate models,the results presented in this study can become a basis to refine the quantification of urban climate parameters,thereby introducing the urban heterogeneity to help understand the climate response of future urbanization.

关键词： Convolutional autoencoder Self-Organizing Map(SOM) Gaussian Mixture Model(GMM) urban form clustering

Primary stage of solar energy use in architecture-Shadow control

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Journal of Central South University 2012年第3期19卷 755-763页

作者： M.Tahbaz school of Architecture and Urban planning Shahid Beheshti University

In architecture and urban design,solar energy plays an important role to save fossil energy and preserve *** or active use of this energy needs especial consideration in the preliminary stage of design to the probable *** work will answer two questions:1) How is it possible to distinguish shadow need periods during a year in a specific climate-2) How is it possible to produce shadow in hot periods without being deprived of pleasant sunshine in cold periods-In this regard,it will introduce the usage process and opportunities of "shading mask" of Olgyay as an easy and useful graphical method in six *** the end,different ways of using this method in design will be *** research projects that have been done in past 30 years will support the argument as examples of this method.

关键词： shading mask sun-path chart shadow angle protractor thermal comfort climatic needs calendar

Genetic algorithms for determining the parameters of cellular automata in urban simulation

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Science China Earth Sciences 2007年第12期50卷 1857-1866页

作者： LI Xia YANG QingSheng LIU XiaoPing school of Geography and planning Sun Yat-sen University Guangzhou 510275 China School of Geography and Planning Sun Yat-sen University Guangzhou 510275 China School of Geography and Planning Sun Yat-sen University Guangzhou 510275 China

This paper demonstrates that cellular automata(CA) can be a useful tool for analyzing the process of many geographical *** are many studies on using CA to simulate the evolution of *** dynamics is determined by many spatial *** contribution of each spatial variable to the simulation is quantified by its parameter or *** procedures are usually required for obtaining a suitable set of parameters so that the realistic urban forms can be *** pa-rameter has a unique role in controlling urban morphology in the *** this paper,these pa-rameters for urban simulation are determined by using empirical *** algorithms are used to search for the optimal combination of these *** are spatial variations for urban dynam-ics in a large *** sets of parameters can be used to represent the unique features of urban dynamics for various subregions.A further experiment is to evaluate each set of parameters based on the theories of compact *** is considered that the better set of parameters can be identified ac-cording to the utility function in terms of compact *** set of parameters can be cloned to other regions to improve overall urban *** original parameters can be also modified to produce more compact urban forms for planning *** approach can provide a useful ex-ploratory tool for testing various planning scenarios for urban development.

关键词： Cellular automata, genetic algorithms, planning scenarios, compact development

Changing Concepts of City and Urban planning Practices in Guangzhou(1949–2010): An Approach to Sustainable Urban Development

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Chinese Geographical Science 2014年第5期24卷 607-619页

作者： XUE Desheng HUANG Gengzhi GUAN Jingwen LIN Jiarong school of Geography and planning Sun Yat-sen University

By focusing on Guangzhou, this paper examines how different concepts of city in terms of urban-rural relationships are shaped in transforming China since 1949, and explores how they influence the way in which urban planning are practiced. In the pre-reform era, the city was defined as a productive space under the system of urban-rural segregation established for securing rapid industrialization. Urban planning was thus only concerned with the development of urban areas. In the 1980 s and 1990 s after the reform, institutional change and economic transformation mobilized the urban-rural linkages. The development of suburban areas was then considered by urban planning, but this consideration was a passive response to urban problems such as population explosion and water resources protection. Since the new millennium, the agenda for sustainable development and problems of uneven urban-rural development have called for the development of urban-rural integration. In this context, the city is conceptualized as a complex of mountain, city, river, farmland and sea, reconstructing the ideology of urban-rural division in defining urban development. Urban planning has therefore sought in an active way to develop a sustainable city embracing rural and natural elements, and to balance economic growth and environmental protection. It is argued that developing the concept of city as a complex of urban and rural elements contributes to the urban planning for sustainable urban development, while this conceptualization relies on the recognition of the integrated urban-rural relationship.

关键词： urban-rural relationship concept of city urban planning sustainable urban development Guangzhou

Articulating China's Science and Technology:Knowledge Collaboration Networks Within and Beyond the Yangtze River Delta Megalopolis in China

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Chinese Geographical Science 2018年第2期28卷 247-260页

作者： LI Yingcheng Nicholas A.PHELPS school of Architecture Southeast University Bartlett school of planning University College London

In this paper, we reconsider the defining but often overlooked ‘hinge' function of megalopolises by analyzing how megalopolises have articulated national and international urban systems in the context of a globalizing knowledge economy. Taking the case of China's Yangtze River Delta(YRD) region, we particularly focus on knowledge circulation within and beyond the YRD region by analyzing the pattern and process of knowledge collaboration at different geographical scales during the 2004–2014 period. Results show that the structure of scientific knowledge collaboration as reflected by co-publications has been strongest at the national scale whereas that of technological knowledge collaboration as measured by co-patents has been strongest at the global scale. Despite this difference, the structure of both scientific and technological knowledge collaboration has been functionally polycentric at the megalopolitan scale but become less so at the national and global scales. The ‘globally connected but locally disconnected' pattern of Shanghai's external knowledge collaboration suggests that the gateway role of the YRD megalopolis in promoting knowledge collaboration at different geographical scales will take time before it is fully realized.

关键词： urban network publication patent scale gateway Yangtze River Delta (YRD)

Effects of urban square entry layouts on spatial ventilation under different surrounding building conditions

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Building Simulation 2021年第2期14卷 377-390页

作者： Wei You Wowo Ding school of Architecture and Urban planning Nanjing UniversityNanjing210093China

Effective urban square ventilation is important for the living comfort and health of *** research aims to establish some principles of street entry layouts for urban square ventilation *** computational fluid dynamics(CFD)simulation techniques,two types of street entry squares(two-intersection and four-intersection)were investigated under the effect of surrounding *** indices—the spatial mean velocity(),air change rate(ACH)and mean flow rates()through the street entry and square roof—were calculated to quantify the square ventilation *** simulation results indicate that the surrounding buildings could influence the square space *** the surrounding building conditions change to a building coverage ratio of 0.25,theentering through the street entry can be reduced by 35%,and thewithin the square decreases by more than 45%.The optimal street entry layout design depends greatly on the wind *** the wind direction is perpendicular to the square street entry,the corner oblique-entry layout square shows a better ventilation performance than the other *** the wind direction is oblique to the square street entry,thedeclines greatly(up to 68%),and the lateral-entry layout design shows the best ventilation performance.

关键词： urban square street entry layout surrounding building spatial ventilation numerical simulation

Mapping the urban natural ventilation potential by hydrological simulation

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Building Simulation 2021年第2期14卷 351-364页

作者： Ziyu Tong Yu Luo Juelun Zhou school of Architecture and Urban planning Nanjing UniversityNanjing210093China

Urban wind environments are closely related to air pollution and outdoor human *** urban natural ventilation potential(NVP)is an important factor in urban planning and ***,for ventilation studies on urban scales,neither macroscale numerical simulations(i.e.,WRF,MM5,etc.)nor microscale computational fluid dynamics(CFD)simulations can conduct efficient *** on the similarity between water flows and airflows,an efficient approach is proposed in this paper to map the urban *** integrating the urban terrain model,urban form model,and prevailing wind pressure model,an airflow digital elevation model(AF-DEM),which represents the resistance to airflow and can be used for a hydrological simulation,is generated and applied to evaluate the urban airflow patterns under different terrain,urban form and ambient wind *** objective was to develop a simulation platform that can efficiently predict the distribution of natural ventilation corridor and *** stream network calculated through the simulation is regarded as potential ventilation corridors within the city,and an index calculated from the coverage rate of wind corridors(CRW)is proposed for evaluating the relative *** Nanjing as a case study,8 AF-DEMs based on different wind directions and wind speed conditions are generated,and their corresponding ventilation corridor maps are *** results are in good agreement with the empirical evidence,indicating that the hydrological model,though a rudimentary approximation of the actual airflows,was effective in revealing the natural ventilation corridor and characterize the relative ***,the implementation of this novel method is simple and convenient,and it has great application potential and value in urban design and management.

关键词： urban natural ventilation potential hydrological simulation airflow DEM local climate zone