ارزیابی تاثیر معیارهای اقلیمی طراحی مدل جغرافیایی میدان شهری براساس کیفیت و جهت یابی باد غالب به منظور دستیابی به آسایش حرارتی مطالعه موردی : میدان نبوت شرق تهران

آسایش حرارتی در فضاهای باز یکی از مسائل مهم و تاثیرگذار برجنبه های مختلف زندگی به ‌شمار می ‌رود. با توجه به این ‌که تهویه طبیعی فضاهای عمومی شهری و میادین  توسط جریان هوای طبیعی، یکی از بهترین و ارزان ‌ترین روش ‌های تهویه می‌ باشد که با ورود باد در فضای میدان صورت می ‌پذیرد و موجب آسایش در فضاهای شهری می‌ شود، از این ‌رو پژوهش پیش ‌رو با توجه به تاثیر باد مطلوب در کیفیت آسایش حرارتی در فضاهای عمومی شهری به ارزیابی و مقایسه ی  معیارهای تاثیر گذار در مدل ‌های ساختاری و کالبدی میدان نبوت واقع در شرق تهران پرداخته است.  این مطالعه، بر اساس کیفیت و جهت ‌یابی باد مطلوب با هدف تعیین مهم ‌ترین و تاثیرگذارترین معیار در مدل ‌یابی جغرافیایی میدان شهری، ضمن ارائه سناریوهایی با تغییر چند فاکتور جهت، سرعت و کیفیت باد مطلوب و مناسب در فضای عمومی شهری، در محیط envimet 4 basic با شبیه ‌سازی سه ‌بعدی و سنجش شرایط خرد اقلیم شهری، سنجش سطح آسایش حرارتی بر مبنای معیار pmv  ( میانگین دمای پیش ‌بینی شده در فضای مدل ‌سازی )  در میدان را انجام داده است.  نتایج حاصل از پژوهش نشان داد که جهت ‌گیری مناسب در شهر تهران برای محوطه ‌های عمومی شهری، جهت جنوب ‌غربی (رون تهرانی)  است.  بر اساس نتایج حاصل از تحلیل نمونه ‌هامشخص شد که گردش حدود 10 درجه نسبت به شمال، بهترین جهت آسایش حرارتی بر اساس بهره ‌گیری از باد غالب شهر است.

Evaluating the impacts of climatic factors, especially quality and direction of the prevailing wind on thermal comfort using geographical models of a town square Case study: Nabovat Square in East of Tehran

IntroductionDevelopment of cities and vehicles used in urban areas have resulted inenvironmentalcrisisin most metropolises all over the world and caused physical and psychological damages to the residents of those areas. Comfort, especially thermal comfort, is one of the main factorsaffectingquality of space and people’s satisfaction in using that space. Thus, it is necessary to create a suitable environment for human beings through protection against adverse climatic conditions. Providing thermal comfort in open urban spaces is an important principle of urban planning, which affects physical and mental health of human beings and consequently, improves their performance. Compared toindoor and private spaces, fewer researches have focused on thermal conditions of public space, which is most possibly due tospatial diversity, wide range of activities performed in open spacesin urban areas, andthe complexity of parameters affecting outdoor comfort.Urban spaces are the scene in which the story of collective life unfolds. Thermal comfort in these areas is considered to be one of the most important and influential issues in various aspects of life. Natural ventilation in public urban spaces and squares is one of the best and cheapest methods of ventilation in which wind enters the urban square and its surrounding space resulting in thermal comfort of people in that area . Materials & MethodsThe present study evaluates and compares the impacts of two effective criteria of quality and direction of prevailing wind on thermal comfort in urban public spaces. These criteria are usedin a structural and physical model ofNabovat Square in east of Tehran with the aim of determining the most important and effective criterion in geographical modeling of urban squares.Therefore, different scenarios are defined changing several factors of direction, speed and wind quality in urban space in ENVImet 4 basic environment.Through a threedimensional simulation and measurement of urban microclimatic conditions,the level of thermal comfort in the study area is measured based on the PMV criterion (average temperature predicted in the modeling space). Results & DiscussionResults indicate that identifying optimal geographical and geometric orientation of a building can play an effective role in getting the maximum benefits of prevailing wind while minimizing possible hazards of high winds, and thus creating thermal comfort for citizens. Another important issue is the effect of wind direction on urban public spaces. This is one of the main factors preventing an increase in the temperature range for comfort, and thus a proper direction of the prevailing wind will lead to thermal comfort in the study area. ConclusionResults of quantitative analysis inENVImet 4 basic environment indicate that the most appropriate orientation of public urban spacesin Tehran is southwestwith a rotation of about 10 degrees. Assuming that several factors such as vegetation and physical properties of the surrounding buildings are constant, the present study has evaluated the impact of factors related to the direction, quality and wind speed. The impact of other factors should be considered in future studies. Finally, it is suggested that planting trees in a suitable place can decrease direct radiation and along with thespecific properties of buildings surrounding the square provide thermal comfort for citizens.In other words, surrounding buildings and the vegetation create an independent microclimate affecting thermal comfort.