تاثير حرارتي – ادراكي شاخص ضريب آسمان قابل رويت با توجه به جهت گيري معابر شهري(نمونه موردي : معابر شهر اصفهان)

The heating and feeling effect of Sky View Factor (SVF) based on the direction of urban streets (Case study: Isfahan streets)

زﻣﯿﻨﻪ و ﻫﺪف: رﺷﺪ ﺷﻬﺮﻧﺸﯿﻨﯽ ﭘﯿﺎﻣﺪﻫﺎي ﻣﺘﻌﺪدي ﺑﻪ ﻫﻤﺮاه داﺷﺘﻪ اﺳﺖ ﮐﻪ از آن ﺟﻤﻠﻪ اﻓﺰاﯾﺶ دﻣﺎي ﺷﻬﺮﻫﺎ اﺳﺖ. در ﻧﺘﯿﺠﻪ اﻓﺰاﯾﺶ اﺳﺘﻔﺎده از ﺧﻨﮏ ﮐﻨﻨﺪه ﻫﺎي ﻣﮑﺎﻧﯿﮑﯽ و ﻣﺼﺮف اﻧﺮژي، ﻣﺸﮑﻼت زﯾﺴﺖ ﻣﺤﯿﻄﯽ و ﺳﻼﻣﺘﯽ از ﺗﺒﻌﺎت ﮔﺮﯾﺰﻧﺎﭘﺬﯾﺮ اﺳﺖ. ﺿﺮورت اﺳﺘﻔﺎده از روش ﻫﺎي ﺗﻌﺪﯾﻞ ﺣﺮارت در ﻃﺮاﺣﯽ ﺷﻬﺮﻫﺎي ﭘﺎﯾﺪار ﺧﺼﻮﺻﺎ ﺗﻨﻈﯿﻢ ﺗﺎﺑﺶ درﯾﺎﻓﺘﯽ ﻣﻮرد ﺗﺎﮐﯿﺪ اﺳﺖ. در اﯾﻦ راﺳﺘﺎ ﺷﺎﺧﺺ ﺿﺮﯾﺐ آﺳﻤﺎن ﻗﺎﺑﻞ روﯾﺖ )(SVF ﺑﻪ ﻋﻨﻮان ﺷﺎﺧﺼﯽ ﮐﻤﯽ ﭘﯿﺸﻨﻬﺎد ﻣﯽ ﮔﺮدد. اﯾﻦ ﭘﮋوﻫﺶ ﺑﻪ دﻧﺒﺎل ﺗﺒﯿﯿﻦ ﻧﻘﺶ اﯾﻦ ﺷﺎﺧﺺ در اﻗﻠﯿﻢ ﺷﻬﺮي اﺳﺖ. از آﻧﺠﺎ ﮐﻪ ﻣﻌﺎﺑﺮ ﺷﻬﺮي ﺑﯿﺶ ﺗﺮﯾﻦ ﻓﻀﺎﻫﺎي ﺷﻬﺮي را ﺷﺎﻣﻞ ﺷﺪه و در ﺗﻨﻈﯿﻢ ﺣﺮارﺗﯽ ﺷﻬﺮ اﻫﻤﯿﺖ دارﻧﺪ، ﻣﻌﺎﺑﺮ در اﻗﻠﯿﻢ ﮔﺮم و ﺧﺸﮏ اﺻﻔﻬﺎن( در دو راﺳﺘﺎي ﺷﻤﺎﻟﯽ ﺟﻨﻮﺑﯽ و ﺷﺮﻗﯽ ﻏﺮﺑﯽ ﻣﻮرد ﺑﺮرﺳﯽ ﻗﺮار ﮔﺮﻓﺘﻪ اﻧﺪ. روش ﺑﺮرﺳﯽ: دو ﺷﯿﻮه ﺑﺮرﺳﯽ ﻫﺎي ﻣﯿﺪاﻧﯽ و ﺷﺒﯿﻪ ﺳﺎزي ﮐﺎﻣﭙﯿﻮﺗﺮي ﻣﻮرد اﺳﺘﻔﺎده ﻗﺮارﮔﺮﻓﺖ. ﺑﺮداﺷﺖ ﻣﯿﺪاﻧﯽ در 17 ﻣﻌﺒﺮ ﺑﺎ ﻋﺮض، ﻣﺤﺼﻮرﯾﺖ ﻫﺎ و ﻣﯿﺰان ﭘﻮﺷﺶ ﻣﺘﻨﻮع در ﺗﺎﺑﺴﺘﺎن 93 ﺻﻮرت ﭘﺬﯾﺮﻓﺖ. در ﻧﺮم اﻓﺰار ENVI-met، 5 ﮔﻮﻧﻪ ﺳﺎزﻣﺎن دﻫﯽ ﮔﯿﺎﻫﯽ در ﺳﻪ محصوريت 1،1/2 و 1/4 شبيه سازي شد تا SVF به تفكيك گياهي و كالبدي بررسي گردد. سه مرحله جمع آوري داده، محاسبه SVF (در برداشت هاي ميداني با محاسبه (Rayman، همگن سازي داده ها و در نهايت تحليل آماري و منطقي در هر دو شيوه انجام شد.ﯾﺎﻓﺘﻪ ﻫﺎ: ﺣﺪاﻗﻞ ﺿﺮﯾﺐ آﺳﻤﺎن ﻗﺎﺑﻞ روﯾﺖ ﻣﻄﻠﻮب ﺑﺮاي اﺻﻔﻬﺎن 0/6 اﺳﺖ ﮐﻪ ﻣﯽ ﺗﻮاﻧﺪ ﺑﺎ ﮔﯿﺎه و ﯾﺎ ﺳﺎﺧﺘﻤﺎن اﯾﺠﺎد ﺷﻮد. از ﻃﺮف دﯾﮕﺮ ﻣﻮﺛﺮ ﺗﺮﯾﻦ ﺿﺮﯾﺐ در ﮐﺎﻫﺶ دﻣﺎ ﺿﺮﯾﺐ ﻫﺎي ﮐﻢ ﺗﺮ از 0/2 ﻣﯽ ﺑﺎﺷﻨﺪ، ﺑﻨﺎﺑﺮاﯾﻦ وﺟﻮد ﺳﺎﺑﺎط ﻫﺎ ﺑﺎ SVF در ﺣﺪود ﺻﻔﺮ در اﯾﻦ اﻗﻠﯿﻢ ﺗﻤﻬﯿﺪ ﺳﻨﺘﯽ ﻫﻮﺷﻤﻨﺪاﻧﻪ اي ﺑﻮده اﺳﺖ. ﺑﺤﺚ و ﻧﺘﯿﺠﻪ ﮔﯿﺮي: از ﻧﺘﺎﯾﺞ اﯾﻦ ﭘﮋوﻫﺶ ﺗﺎﺛﯿﺮ ﻣﺴﺘﻘﯿﻢ و ﺑﯿﺶ ﺗﺮ SVF ﺑﺮ دﻣﺎي ﺗﺎﺑﺶ، دﻣﺎي ﺳﻄﺢ، دﻣﺎي ﺑﯿﻮﻟﻮژﯾﮏ ، اﺣﺴﺎس ﺣﺮارﺗﯽ و در ﻣﻘﺎﯾﺴﻪ ﺑﺎ دﻣﺎي ﻫﻮا ﻣﯽ ﺑﺎﺷﺪ. ﮐﻪ ﻣﺒﯿﻦ ﻧﺎﮐﺎرا ﺑﻮدن دﻣﺎي ﻫﻮا ﺑﻪ ﻋﻨﻮان ﺗﻨﻬﺎ ﻣﺘﻐﯿﺮ ﺑﺮرﺳﯽ ﺗﻌﺪﯾﻞ ﺣﺮارت ﺷﻬﺮﻫﺎﺳﺖ. ﺗﺎﺛﯿﺮ اﯾﻦ ﺷﺎﺧﺺ در ﻣﻌﺎﺑﺮ ﺷﺮﻗﯽ ﻏﺮﺑﯽ ﺑﯿﺶ ﺗﺮ از ﺷﻤﺎﻟﯽ ﺟﻨﻮﺑﯽ ﺑﻮده و ﺗﻌﺪﯾﻞ ﺣﺮارﺗﯽ ﺑﺎ ﺷﯿﻮه ﮐﺎﻟﺒﺪي ) اﻓﺰاﯾﺶ ﺗﺮاﮐﻢ و ارﺗﻔﺎع ﮐﺎﻟﺒﺪ ﭘﯿﺮاﻣﻮن ﻣﻌﺎﺑﺮ( در ﻣﻌﺎﺑﺮ ﺷﻤﺎﻟﯽ ﺟﻨﻮﺑﯽ و اﺳﺘﻔﺎده از ﭘﻮﺷﺶ ﺳﺒﺰ ﺳﺎﯾﻪ اﻧﺪاز در ﻣﻌﺎﺑﺮ ﺷﺮﻗﯽ- ﻏﺮﺑﯽ ﮐﺎرا ﺗﺮﯾﻦ اﺛﺮ را در ﺗﻌﺪﯾﻞ ﺣﺮارت دارﻧﺪ.

Background and Objective: Growing urbanization has different consequences which one of them is increasing the temperature of cities thus, more usage of mechanical air-condition, more energy consumption and environmental and health consequences are inevitable. The necessity of thermal mitigating methods in designing sustainable cities, especially by adjusting received radiation, has been emphasized. Therefore, Sky View Factor (SVF) as a quantitative index has been proposed. Considering the fact that, urban streets have the largest area among other urban spaces and play an important role in thermal comfort in cities, streets in hot and dry climate (Isfahan) in two directions of N-S and E-W were selected. Method: In this study, field studies and simulation have been applied. Field study has been conducted in 17 streets with different width, closeness and green coverage, in summer 2014.. In ENVI-met 5 green arrangements in 3 closeness scale (1, 1/2, ¼) were simulated to investigate green and physical SVF separately. Data gathering, calculating SVF (Rayman has been applied in field study), homogenizing data and statistical and logical analysis between variations, in the procedure applied in both methods. Findings: The minimum SVF, which is effective to heat mitigation in Isfahan, is 0.6, which can be greenery or buildings. In addition, the most effective SVF is less than 0.2. As a result, Sabat with SVF equals to zero have been a traditional smart choice in this climate. Discussion and Conclusion: Finally, the results indicate a relatively high accuracy of three methods in estimating the transmission potential for land use and land cover changes, but according to the kappa coefficients, the accuracy of Similarity Weighted Instance based Learning method more than the other two methods.