Investigating the arrangement of buildings and towers to prevent the concentration of air pollution in the air of the metropolis of Tabriz

Dissertation for Master's Degree

Field: Mechanical Engineering

Abstract:

            Nowadays, due to the increase in population in big cities, perhaps the construction of high-rise buildings and residential towers is inevitable. to seem But in locating these types of buildings and placing them together, a series of environmental requirements must be observed.  In this thesis, an attempt has been made to re-evaluate the different patterns of high-rise buildings and their arrangement in a city such as Tabriz, so that with the smallest possible wind, the process of leaving the pollutants caused by the smoke of cars and industries from the city is facilitated. It is hoped that by observing simple but fundamental and vital principles, we can leave clean air to the future generations in the hope of that day.

Key words:

Wind, prevailing wind speed, turbulence, mixing, air flow lines, distance between buildings, Arrangement of buildings

1 Introduction

Today, due to the excessive growth of the population and the need for housing, it has required that tall buildings rise like mushrooms every day from the corners of the city. Previously, there were maybe 20 households in an 8-meter neighborhood. but now according to the municipality's permits and engineering system, at least 80 households live in all the cities. Now this problem increases the emissions in the cities. Because the increase in the number of single-passenger cars causes problems in this regard, the weather in Azar Bayjan was pleasant and cool. Time has caused changes in the climate of the region and now the increase in temperature has caused the former climate to no longer exist. Snowfalls and rains have decreased and even the winds have decreased.   But the amount of pollution increases every day compared to the previous day.  The constructions have reduced the green space in the city and the drought has dried the trees in the city.

All air pollutants emitted from point and surface sources are transferred, dispersed or concentrated by atmospheric and topographical conditions. The cycle of pollutant transmission by air begins with the emission of pollutants, followed by their transmission and distribution throughout the atmosphere. This cycle is completed when pollutants are released into the atmosphere and are deposited on the surfaces of plants, animals, soil, water and other objects through rain. In some cases, these pollutants may be re-entered by the wind. In areas such as big cities where topographical and atmospheric conditions cause condensation and accumulation of pollutants, pollutants may accelerate the destruction of buildings and have harmful effects on the health of the public as well as plants in the area. Photochemical smog, which causes eye irritation, is formed by the interaction of nitrogen oxides, hydrocarbons and solar energy in the atmosphere. The results of such changes are not always harmful but sometimes they are beneficial. Some mineral salts, which are essential for plant life, are examples of such a situation. In large urban areas, diffuse pollutants, resulting from numerous sources, are concentrated and surface sources are scattered over the entire geographical area. Every certain place in the urban area receives pollutants from different sources in different amounts. Therefore, the amount of transfer or emission of pollutants in each region depends on the prevailing wind speed and the presence of tall buildings. If the concentration of a pollutant in an area does not exceed the permissible limit, the contribution of each of the separate sources and surface sources should be determined.

In this thesis, considering the geographical location of the Tabriz region, in order to reduce the concentration of pollutants in the city, the arrangement of buildings and towers has been investigated in order to prevent the concentration of air in the city.  The question that is raised in this thesis is whether it is possible to allow the wind to blow in the buildings and towers with a regular and clear arrangement, to remove the pollution from the top of Tabriz city? What are the assumptions of the problem? In this thesis, it has been tried to arrange the tall buildings and towers in such a way that the wind or breeze that blows in the city can travel more in the city and with this travel, it can have an optimal level of transmission, diffusion and dispersion of pollution. For this purpose, first the old texture and the new texture of the city are examined and then the appropriate patterns are found and they are simulated until the appropriate result is obtained, but before that, a brief look at the process of wind production and the factors affecting its movement is examined, because the main process in this research is the flow of wind and the arrangement of buildings.  ]1[

Solar radiation 1-2

       At the upper limit of the Earth's atmosphere, the amount of vertical radiation of the sun, which is called the solar constant, is 8.16. The maximum intensity occurs at wavelengths between 0.4 µm and 0.8 µm, which is the basis of the visible part of the electromagnetic spectrum.

Approximately 42% of this energy is absorbed by the upper atmosphere or reflected into space through clouds or scattered upward by the atmosphere or radiated by the surface of the earth or finally by water vapor. is absorbed Approximately 47% of the sun's rays are absorbed by the water and land surfaces of the earth. The earth as an object at a temperature of approximately 17 degrees Celsius emits long-wavelength rays whose maximum intensity is between µm4 and µm12 (near the infrared region). A large amount of this radiation is absorbed by water vapor and carbon dioxide in the atmosphere near the earth's surface. to be Since water vapor and carbon dioxide absorb part of the solar radiation, they absorb the long-wavelength radiation from the surface of the earth.  Therefore, the overall effect causes atmospheric warming, which is called the Golkhane effect.

On the other hand, one of the results of the industrialization of the world is a significant increase in the emission of particulate matter. Suspended substances in the atmosphere prevent the passage of solar radiation towards the earth's surface. This effect is the opposite of the effect of increased concentrations of carbon dioxide and water vapor in the atmosphere. This means that this effect reduces the average atmospheric temperature. If the pollutants released by humans are not fundamentally controlled, it is difficult to predict which of these two factors will overshadow atmospheric temperatures in the coming decades. ]1[

1-3 Wind Circulation

The Sun, the Earth and the Earth's atmosphere form a huge dynamic system. The air temperature difference leads to horizontal pressure gradients, which in turn causes the horizontal movement of the ground level. Therefore, the temperature difference between the polar and equatorial atmospheres, as well as the atmosphere over the continents and over the oceans, causes air movement on a large scale. If the earth was not rotating, air would tend to flow directly from high pressure areas to low pressure areas. Another wind parameter that is considered in meteorology is the wind gradient, which is related to pressure curves.  In the curved paths of the wind movement in the earth's atmosphere and around the high-pressure and low-pressure areas, the wind speed is not constant and always has a central acceleration known as ac for the wind. Such curved paths are observed especially around high pressure low pressure areas. In the Northern Hemisphere, the counterclockwise movement of air in the low pressure center is called silcon, and the clockwise movement around the high pressure center is called antisilcon. Figure 1-1 The ac vector of the centripetal acceleration inward of the rudder shows a curve of radius r. At the prominent high-pressure edges and low-pressure troughs in the atmosphere (where a significant bend has occurred in the closed air path), the gradient wind speed is a better approximation than the geostrophic wind speed for the real wind situation.