مطالعه آزمايشگاهي و عددي نشت در روزنه هاي لوله هاي پلي اتيلن

Experimental and Numerical Study on Leakage in Orifices of High-Density Polyethylene Pipe

زﻣﯿﻨﻪ و ﻫﺪف: ﯾﮑﯽ از ﻣﺆﺛﺮﺗﺮﯾﻦ روش ﻫﺎي ﻣﻘﺎﺑﻠﻪ ﺑﺎ ﻧﺸﺖ در ﺷﺒﮑﻪ ﻫﺎي ﺗﻮزﯾﻊ آب، ﻣﺪﯾﺮﯾﺖ ﻓﺸﺎر ﻣﯽ ﺑﺎﺷﺪ و ﻟﺬا درك ﺻﺤﯿﺢ از رﻓﺘﺎر ﻧﺸﺖ و راﺑﻄﻪ آن ﺑﺎ ﺗﻐﯿﯿﺮات ﻓﺸﺎر ﻣﯽ ﺗﻮاﻧﺪ ﻧﻘﺶ ﺑﺴﺰاﯾﯽ در ﮐﻨﺘﺮل ﺗﻠﻔﺎت داﺷﺘﻪ ﺑﺎﺷﺪ. اﺳﺘﻔﺎده از ﻟﻮﻟﻪ ﻫﺎي ﭘﻠﯽ اﺗﯿﻠﻦ ﭼﮕﺎﻟﯽ ﺑﺎﻻ )HDPE( در ﺳﺎل ﻫﺎي اﺧﯿﺮ در ﺷﺒﮑﻪ ﻫﺎي ﺗﻮزﯾﻊ آب ﺑﺴﯿﺎر اﻓﺰاﯾﺶ ﯾﺎﻓﺘﻪ و در ﺑﺮﺧﯽ روﺳﺘﺎﻫﺎ و ﺷﻬﺮﻫﺎي ﮐﻮﭼﮏ ﺑﻪ ﺻﻮرت ﮐﺎﻣﻞ از اﯾﻦ ﻧﻮع ﻟﻮﻟﻪ ﻫﺎ اﺳﺘﻔﺎده ﺷﺪه اﺳﺖ. ﻫﺪف از اﯾﻦ ﻣﻄﺎﻟﻌﻪ ﺷﻨﺎﺧﺖ رﻓﺘﺎر ﻧﺸﺖ از روزﻧﻪ ﻫﺎ در ﻟﻮﻟﻪ ﻫﺎي ﭘﻠﯽ اﺗﯿﻠﻦ ﻣﯽ ﺑﺎﺷﺪ. روش ﺑﺮرﺳﯽ: در ﻣﻄﺎﻟﻌﻪ ﺣﺎﺿﺮ رﻓﺘﺎر ﻧﺸﺖ روزﻧﻪ اي در ﻟﻮﻟﻪ ﻫﺎي ﭘﻠﯽ اﺗﯿﻠﻦ ﺑﻪ ﺻﻮرت آزﻣﺎﯾﺸﮕﺎﻫﯽ و ﻋﺪدي ﺑﺮرﺳﯽ ﺷﺪه اﺳﺖ. در اﯾﻦ ﻣﻄﺎﻟﻌﻪ ﺗﺄﺛﯿﺮ ﭘﺎراﻣﺘﺮ دﻣﺎ ﺑﻪ ﻋﻨﻮان ﯾﮑﯽ از ﻋﻮاﻣﻞ اﺻﻠﯽ ﺑﺮ رﻓﺘﺎر ﻧﺸﺖ ﻣﻮرد ﻣﻄﺎﻟﻌﻪ ﻗﺮار ﮔﺮﻓﺘﻪ اﺳﺖ. ﯾﺎﻓﺘﻪ ﻫﺎ: ﻧﺘﺎﯾﺞ ﺑﻪ دﺳﺖ آﻣﺪه ﻧﺸﺎن داد اﺳﺘﻔﺎده از راﺑﻄﻪ ﮐﻼﺳﯿﮏ ﺗﻮرﯾﭽﻠﯽ ﺑﺮاي روزﻧﻪ ﮐﺎرﺑﺮد دارد و ﻣﻘﺪار ﺗﻮان ﻧﺸﺖ ﺑﺮاي روزﻧﻪ ﻫﺎ ﺗﻘﺮﯾﺒﺎً 0/5 ﻣﯽ ﺑﺎﺷﺪ. در اﯾﻦ ﻣﻄﺎﻟﻌﻪ ﻫﻤﭽﻨﯿﻦ ﻧﺸﺎن داده ﺷﺪ ﺿﺮﯾﺐ ﺗﺨﻠﯿﻪ ﺟﺮﯾﺎن ﺧﺮوﺟﯽ از روزﻧﻪ ﺑﻪ ﻋﻮاﻣﻠﯽ ﻧﻈﯿﺮ ﻋﺪد رﯾﻨﻮﻟﺪز، ﺿﺨﺎﻣﺖ ﺟﺪاره ﻟﻮﻟﻪ، ﻗﻄﺮ روزﻧﻪ، ﻣﺤﯿﻂ ﭘﯿﺮاﻣﻮﻧﯽ و ﺗﻐﯿﯿﺮ ﺷﮑﻞ روزﻧﻪ واﺑﺴﺘﻪ اﺳﺖ. ﺑﺤﺚ و ﻧﺘﯿﺠﻪ ﮔﯿﺮي: ﺑﺎ اﻓﺰاﯾﺶ ﻓﺸﺎر، ﻓﺮض ﻋﺪم ﺗﻐﯿﯿﺮ ﺷﮑﻞ ﺑﺮاي روزﻧﻪ در ﻟﻮﻟﻪ ﻫﺎي ﭘﻠﯽ اﺗﯿﻠﻦ ﺑﻪ ﺧﺼﻮص در دﻣﺎي ﺑﺎﻻ اﻟﺰاﻣﺎً ﺻﺎدق ﻧﯿﺴﺖ. روزﻧﻪ در ﻟﻮﻟﻪ ﻫﺎﯾﯽ ﺑﺎ اﻻﺳﺘﯿﺴﯿﺘﻪ ﭘﺎﯾﯿﻦ ﺑﺎ ﺗﻮﺟﻪ ﺑﻪ ﻧﻮع ﺗﻮزﯾﻊ ﺗﻨﺶ در ﻣﺤﻞ ﺑﺎزﺷﺪﮔﯽ و ﻫﻤﭽﻨﯿﻦ ﺗﺄﺛﯿﺮ ﺿﺮﯾﺐ ﭘﻮاﺳﻮن ﺑﺎ اﻓﺰاﯾﺶ ﻓﺸﺎر از ﺣﺎﻟﺖ ﺗﻘﺎرن ﺧﺎرج ﺷﺪه و در ﻧﺘﯿﺠﻪ ﺑﺎﻋﺚ ﮐﺎﻫﺶ ﺿﺮﯾﺐ ﺗﺨﻠﯿﻪ ﻣﯽ ﮔﺮدد.

Background and Objective: One of the most effective methods of coping with leakage in water distribution networks is pressure management. Therefore, a proper understanding of leakage behavior and its relationship with pressure variations can play a significant role in water loss control. The use of high-density polyethylene (HDPE) pipes has increased in recent years in water distribution networks so that in some rural area and small cities, these pipes have been utilized only. The aim of this study is to investigate the leakage behavior of orifices in HDPE pipes. Method: In the present study, the leakage behavior of polyethylene pipes has been investigated numerically and experimentally. In this study, the effect of temperature as one of the main factors on leakage behavior has been considered. Findings: The results showed that the Torricelli's classic relationship for the orifices can be used and the amount of leakage exponent for the orifices is approximately 0.5. This study shows that the discharge coefficient of the outflow from the orifices is dependent on some parameters such as Reynolds number, the thickness of pipe wall, orifice diameter, surrounding environment and orifice deformation. Discussion and Conclusion: The assumption of no deformation for the orifices in HDPE pipes with increasing pressure, particularly at high temperatures, is not necessary true. The symmetry state of the orifices in low-elastic pipes is removed with the pressure increase, due to the distribution of stress at the opening and also the effect of the Poisson coefficient, thereby reducing the discharge coefficient.