بررسی آزمایشگاهی ضریب دبی سرریزهای لبه تیز سهموی

نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه مهندسی آب دانشگاه فردوس مشهد

2 گروه مهندسی آب دانشگاه فردوسی مشهد

چکیده

ﺳﺮرﯾﺰﻫﺎ ﺑﻪ زه ﻋﻨﻮان ﯾﮑﯽ از اﺑﺰارﻫﺎی ﺳﺎده اﻧﺪا ﻪ ﮔﯿﺮی ﺷﺪت ﺟﺮﯾﺎن در آﺑﺮاﻫ ﻫﺎی ﮐﻮﭼﮏ و ﻣﺘﻮﺳﻂ و ﯾﺎ در ﺗﺄﺳﯿﺴﺎت ﺻﻨﻌﺘﯽ ﻣﯽ ﺪ ﺑﺎﺷﻨ ﺎ .ﺳﺮرﯾﺰﻫ ﻪ ی ﻟﺒ ﻣﯽ ﺗﯿﺰ ﻞ ﺗﻮاﻧﻨﺪ ﺑﻪ ﺷﮑ ﻫﺎ ﻪ ذوزﻧﻘ ﺮه ، ی ﻣﺨﺘﻠﻔﯽ ﻣﺎﻧﻨﺪ ﻣﺴﺘﻄﯿﻠﯽ، ﻣﺜﻠﺜﯽ  داﯾ ،ای ای  ، و ﺳﻬﻤﻮی ﺳﺎﺧﺘﻪ ﺷﻮﻧﺪ .در ﺣﺎﻟﺖ ﮐﻠﯽ دﺑﯽ ﺟﺮﯾﺎن ﻋﺒﻮری از ت Q Khn اﯾﻦ ﺳﺮرﯾﺰﻫﺎ ﺑﺎ ﻋﺒﺎر =  ﻣﯽ ﺑﯿﺎن  ﺷﻮد .در اﯾﻦ  n  ﺗﻮان ً ﻣﻌﺎدﻟﻪ ﻣﻌﻤﻮﻻ ﺑﺎ ﺷﮑﻞ ﺳﺎﺧﺘﻤﺎن آن ﺗﻐﯿﯿﺮ ﻣﯽ ﺪ ﮐﻨ  و ﻋﺪد ﻏﯿﺮﺻﺤﯿﺢ ﺖ ﻫﺴ )ﺑﻪ ن ﻋﻨﻮا ل 2 ﻣﺜﺎ 3  ﺑﺮای ﺳﺮرﯾﺰﻫﺎی 2 ﻣﺴﺘﻄﯿﻠﯽ و 5 ( ﺑﺮای ﺳﺮرﯾﺰﻫﺎی ﻣﺜﻠﺜﯽ ﮐﻪ  ﻣﺤﺎﺳﺒﻪ دﺳﺘﯽ دﺑﯽ ﺟﺮﯾﺎن را ﺑﺎ ﻣﺸﮑﻞ روﺑﺮوﻣﯽ ﺳﺎزد .در اﯾﻦ ﺗﺤﻘﯿﻖ ﺟﻬﺖ ﺳﻬﻮﻟﺖ ﻪ ﻣﺤﺎﺳﺒﺎت دﺑﯽ از روی ﺳﺮرﯾﺰﻫﺎی ﻟﺒ  ﻣﻌﺎدﻻت ﺣﺎﮐﻢ ﺑﺮ ﺳﺮرﯾﺰﻫﺎی ﺳﻬﻤﻮی ﺳ ،ﺗﯿﺰ ﻣﻮردﺑﺮر ﯽ  ﻗﺮار ﮔﺮﻓﺖ و ﻣﻌﺎدﻟﻪ ای ﺳﺎده و دﻗﯿﻖ ﺟﻬﺖ ﻣﺤﺎﺳﺒﻪ ﻦ ﺷﺪت ﺟﺮﯾﺎن ﺗﻮﺳﻌﻪ داده ﺷﺪ .ﻫﻤﭽﻨﯿ ل ﺑﺎ اﺳﺘﻔﺎده از ﻣﺪ  ﻓﯿﺰﯾﮑﯽ در ﻪ زاوﯾ ﻫﺎ و ارﺗﻔﺎع ﻫﺎی ﻒ  ، ﻣﺨﺘﻠ ﺧﺼﻮﺻﯿﺎت ﻫﯿﺪروﻟﯿﮑﯽ اﯾﻦ ﺳﺮرﯾﺰﻫﺎ ﺳ ﻣﻮردﺑﺮر ﯽ ﺶ ﻗﺮار ﮔﺮﻓﺖ .ﻧﺘﺎﯾﺞ آزﻣﺎﯾ ﻫﺎ ﻧﺸﺎن داد ﮐﻪ ﺑﺎ اﻓﺰاﯾﺶ زاوﯾﻪ و ارﺗﻔﺎع ﺳﺮرﯾﺰ ﻣﯽ ﺿﺮﯾﺐ دﺑﯽ اﻓﺰاﯾﺶ ﺑ ، ﺳﻬﻤﻮی ﯾﺎ ﺶ ﺪ .ﻣﻘﺪار ﻣﺘﻮﺳﻂ اﯾﻦ ﺿﺮﯾﺐ در آزﻣﺎﯾ ﻫﺎی م اﻧﺠﺎ ه ﺷﺪ  ﺑﻪ ه 0/605 دﺳﺖ آﻣﺪ .ﻫﻤﭽﻨﯿﻦ ﺑﺎ اﺳﺘﻔﺎده از داد ﻟﻪ ﻫﺎی آزﻣﺎﯾﺸﮕﺎﻫﯽ ﻣﻌﺎد  رﮔﺮﺳﯿﻮﻧﯽ ﻣﻨﺎﺳﺒﯽ ﺟﻬﺖ ﺗﻌﯿﯿﻦ ﺿﺮﯾﺐ دﺑﯽ از 2 0 922)  ﺑﺎ ﺿﺮﯾﺐ ﺗﺒﯿﯿﻦ ، روی اﯾﻦ ﻧﻮع ﺳﺮرﯾﺰ /R =( ﺑﻪ. دﺳﺖ آﻣﺪ

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Experimental Study of Discharge Coefficient of Parabolic Sharp-Crested Weirs

نویسندگان [English]

  • H Shariati 1
  • S.R Khodashenas 2
چکیده [English]

Weirs provide a simple method for measuring the volumetric flow rate in small to mediumsized streams or in industrial discharge locations. Sharp crest weirs can be built in different shapes, such as rectangular, triangular, trapezoidal, circular and parabolic. In general, the discharge of these weirs is expressed by n KhQ = , where the value of n varies with structure shape (e.g. 3/2 for rectangular weir and 5/2 for triangular weir) and isn’t usually an integer number, then manual calculation of the discharge is facing a problem. In this study to facilitate the discharge calculations, the governing equations of parabolic crest weirs were reviewed and a simple equation was developed for computing the flow rate. Also, by using a physical model with different angles and heights, hydraulic characteristics of these weirs were investigated. The experimental results showed that with increasing the angle and height of parabolic weirs, the discharge coefficient was increased. The average discharge coefficient of experiments was calculated as 0.605. Furthermore, a proper regression-based equation to determine the discharge coefficient, with coefficient of determination R2=0.922, was obtained.

کلیدواژه‌ها [English]

  • Discharge coefficient
  • Discharge equation
  • Flow measurement
  • Open channel
  • Parabolic weir