بررسی رفتار جریان باد و ذرّات معلق (PM2.5, PM10) پیرامون پوسته بلوک های ساختمانی در بافت مسکونی طرح تفصیلی شهر عسلویه (مقاله علمی وزارت علوم)
درجه علمی: نشریه علمی (وزارت علوم)
آرشیو
چکیده
ذرّات معلق پیامدهای مخرب بر سلامت افراد دارند. سرعت باد، فاکتور مهم در تعیین غلظت ذرّات است. هندسه شهری بر سرعت باد و درنتیجه کیفیت هوا تأثیرگذار است. پایش کیفیت هوای شهر ازطریق اندازه گیری ذرّات و پارامترهای جوی صورت می گیرد و تأثیرگذاری بافت بر پراکندگی آلاینده ها لحاظ نمی شود. پژوهش حاضر، با هدف مطالعه رفتار جریان باد و ذرّات معلق پیرامون ساختمان ها در کدهای ارتفاعی، معابر و جبهه های مختلف، در یک بافت مسکونی در شهر عسلویه انجام شد. تأثیر رفتار باد بر پراکندگی ذرّات، همچنین تأثیر ارتفاع، جهت گیری معابر و بناها، بر رفتار باد و ذرّات بررسی شد. سرعت، فشار، آشفتگی، مسیر حرکت باد، و سرعت، غلظت و مسیر حرکت ذرّات، در سطح زمین و ارتفاعات مختلف، معابر هم راستا با جریان باد و عمود بر آن، جبهه های رو و پشت به باد، با شبیه سازی در نرم افزار انسیس فلوئنت نسخه 2021 تعیین شد. در ارتفاعات بالاتر بنا، با افزایش سرعت و تلاطم جریان، طول سایه باد در معابر و جبهه های پشت به باد کاهش یافت. تجمع ذرّات فاقد جرم در جبهه های پشت به باد در محدوده سایه باد مشاهده شد. بیشترین و کمترین غلظت ذرّات معلق به ترتیب در جبهه رو به باد و سایه باد مشاهده شد. یافته ها در مطالعه آسایش حرارتی و مقاومت مصالح با توجه به بار باد در فضاهای شهری نیز سودمند خواهد بود.Investigating the behavior of wind flow and Particulate Matter (PM2.5, PM10) around building block skins in the residential context of Asalouyeh detailed pla
Air pollution negatively affects people's health and the economies of countries. Air pollutants can be categorized into three groups: Particulate Matter (PM), Volatile Organic Compounds, and microorganisms. Particulate Matter is the most important air pollutant, especially in major cities worldwide. Particulate Matter is classified into three groups according to their size: large particles (with a diameter between 2.5-10 microns), fine particles (with a diameter between 0.1-2.5 microns), and ultrafine particles (with a diameter between 0.1 microns and less). The wind flow behavior is an important factor in determining the particle concentrations in urban spaces. On the other hand, the urban geometry affects the wind velocity and consequently the outdoor air quality. Therefore, the proper design of urban context can be beneficial in reducing the impact of air pollution. However, this influence is often overlooked in the guidelines. Outdoor air quality is monitored by measuring particle concentrations and atmospheric parameters and the effect of the context on the dispersion of pollutants is not taken into account. Additionally, there are only a few urban air quality monitoring locations. The concentration of some pollutants (including PM) is determined in these monitoring stations. Therefore, they do not provide sufficient and comprehensive data to control urban air pollution. The Computational fluid dynamics analysis can be used to evaluate the wind flow behavior and pollutant dispersion and as a result, predict the urban air quality. This research aimed to study the behavior of wind flow and PM around buildings at different heights, street canyons, and building sides in a part of the residential context of Asalouyeh City. Accordingly, it investigated the effect of wind flow behavior on particle dispersion as well as the effect of height, and street and building orientation on wind flow behavior and PM dispersion. A section of the residential context in a high-density area was selected as the case study. The wind velocity, pressure, turbulence, flow pathlines, PM velocity and concentration, and particle tracks were defined at ground level, at different heights, in streets aligned with the wind direction and perpendicular to it, and on the windward and leeward side faces using CFD simulation in Ansys-Fluent 2021. An area of 129276 square meters with a length of 378 meters was simulated as a wind tunnel. Findings showed that the buildings act as a windbreak and cause wind velocity to decrease significantly in the leeward side face. As the height increased, resulting in higher wind velocity and turbulence, the length of the wind shadow decreased in the leeward side face. At higher altitudes, as the wind joined the free stream, flow turbulence was reduced. Accumulation of massless particles was observed in the leeward side face in the wind shadow area. The highest and lowest PM concentrations were observed in the windwards and the wind shadow, respectively. Therefore, the PM concentrations follow the wind velocity. Findings can be useful in studying outdoor air quality, as well as evaluating thermal comfort and choosing materials according to wind loads in urban spaces.
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