چكيده به لاتين
By the rapid growth of urbanization and the increasing trend of global population, living in dense cities has become inevitable. At the same time, the traditional approach to urban structures, irrational human interventions and the use of design patterns regardless to their functions and contextual necessities, has converted urban buildings, and consequently cities, to large impedimental masses. This issue, by preventing the infiltration of wind and air flow into the cities and neighborhoods, has ultimately increased the level of air pollution and degraded air quality in urban areas. In this regard, "urban ventilation" has been proposed as a new approach to solve the problem of air quality in cities. The present study, by discussing questions about the ways of applying natural ventilation based patterns and guidelines on cities, aims to provide a comprehensive model to facilitate urban natural ventilation by redefining the mass and space pattern. For this purpose, it has been tried to identify the dimensions of urban natural ventilation, and the effective morphological factors and components in improving urban air quality.
After defining the main framework of the topic by presenting the problem statement, specifying the research’s objectives and questions, and highlighting the research scope and limitations in the first chapter, the theoretical foundations of the research has been conducted in the second chapter. In this chapter, the basic concepts, thematic evolution of the topic, and natural urban ventilation’s different scales have been reviewed, and by presenting five effective factors on natural ventilation, and five affected areas of natural ventilation based on their scale the conceptual model of research, which shows a comprehensive connection among the influential components have been provided. Accordingly, in the third chapter by using the Goeller evaluation matrix, 35 morphological indicators which have been extracted from the literature review have been ranked, and 8 main indicators have been selected as the first priorities to assess the condition of natural ventilation in urban areas (including complementary informations such as: index abbreviation, index component, index direction, etc.). Afterwards, using the research onion model, elements such as: the research’s “philosophy”, “approach”, “strategy”, “choices of methods”, and it’s “time horizons” have been determined, and in the last “data collection and analysis” which are two important and decisive issues in the methodological process, are fully described based on the objectives of the research. In the fourth chapter, at the beginning, the climatic situation of Tehran metropolis has been studied, and the study area is studied based on Tehran’s air quality control company statistics. Then, based on our final eight indicators, the morphological characteristics of the study area are analyzed, and the wind environment has been simulated, and finally, based on the results of the analysis, a proposed model based on natural facilitation solutions for the study area is presented. In the fifth chapter, it has been tried to review the theoretical and practical findings of the research and to reconcile these findings with each other, compiling the framework of urban planning interventions based on natural ventilation requirements, and presenting future suggestions for complementary studies, and conducting more applied research.
The results of theoretical studies indicates properly, that among the dimensions and components affecting the efficiency of urban ventilation, urban morphology as a key component in the field of urban planning, can play a decisive role in wind speed in urban areas. In practice, the results of the analysis and study of the effect of indicators on the average wind speed in the study area and the relationship of each of them with each other show that, among the eight indicators, 3 of them (Building Coverage Ratio, The Standard Deviation of Building Heights and Urban Building Density) were independent Indicators and their decrease or increase directly affects the other 5 indicators as dependent ones (The Street Canyon Density, Plot Ratio, Sky View Factor, Frontal Area Density and Aspect Ratio). According to the quantitative results of measuring the indicators, and their impact’s level of intensity, and based on the theoretical findings of the research, it has been tried to improve the relationships and the pattern of mass and space in the study area, and provide the minimum physical standards based on natural ventilation. The results of the re-evaluation of the proposed pattern of mass and space settlement, by Envy-Met software, shows a relative improvement of conditions, and an increase in the average wind speed in the study area.
