شبيه‌سازي ناحيه جداشدگي در تقاطع چهار شاخه راست گوشه با Flow 3D

Simulation of Separation Zone in Right-Angled Four-branch Junction with Flow 3D

در ﺗﻘﺎﻃﻊﻫﺎي راﺳﺖ ﮔﻮﺷﻪ ﺳﻪ ﺷﺎﺧﻪ ﯾﺎ ﭼﻬﺎر ﺷﺎﺧﻪ ﮐﺎﻧﺎل ﻫﺎي روﺑﺎز، ﻣﻄﺎﻟﻌﻪ ﺟﺪاﯾﯽ ﺟﺮﯾﺎن ﺑﺴﯿﺎر ﺣﺎﺋﺰ اﻫﻤﯿﺖ ﻣﯽﺑﺎﺷﺪ. ﺑﺮﺧﯽ ﭘﺎراﻣﺘﺮﻫﺎي ﻣﻮﺛﺮ در اﯾﻦ زﻣﯿﻨﻪ ﻧﺴﺒﺖ دﺑﯽ ورودي و ﻋﻤﻖ ﺟﺮﯾﺎن ﻣﯽﺑﺎﺷﺪ ﮐﻪ در اﯾﻦ ﺗﺤﻘﯿﻖ ﺗﺎﺛﯿﺮ ﻧﺴﺒﺖ دﺑﯽ ورودي و ﻧﺴﺒﺖ ارﺗﻔﺎع ﺳﺮرﯾﺰﻫﺎ )ﻋﻤﻖ ﺟﺮﯾﺎن( در اﻟﮕﻮي ﺟﺮﯾﺎن و اﺑﻌﺎد ﻧﺎﺣﯿﻪ ﺟﺪاﺷﺪﮔﯽ ﺑﻪ ﺻﻮرت ﻋﺪدي ﺷﺒﯿﻪﺳﺎزي ﺷﺪه اﺳﺖ. ﺑﺮرﺳﯽ ﻧﺘﺎﯾﺞ ﻣﺪل ﻋﺪدي ﻧﺸﺎن داد ﮐﻪ ﻣﺪل k-ωﺑﯿﺸﺘﺮﯾﻦ ﻣﻄﺎﺑﻘﺖ را ﺑﺎ ﻧﺘﺎﯾﺞ آزﻣﺎﯾﺸﮕﺎﻫﯽ دارد، ﺑﻪ ﻃﻮرﯾﮑﻪ ﻣﯿﺰان ﺧﻄﺎي ﺷﺒﯿﻪﺳﺎزي ﮐﻤﺘﺮ از 20% ﺑﻮد. اﺑﻌﺎد ﻧﺎﺣﯿﻪ ﺟﺪاﺷﺪﮔﯽ در ﮐﺎﻧﺎل ﻫﺎي اﺻﻠﯽ و ﻓﺮﻋﯽ ﺑﺎ ﻧﺴﺒﺖ دﺑﯽ ورودي راﺑﻄﻪ ﻣﺴﺘﻘﯿﻢ داﺷﺖ. ﻫﻤﭽﻨﯿﻦ ﺑﺎ اﻓﺰاﯾﺶ ارﺗﻔﺎع ﺳﺮرﯾﺰﻫﺎي ﺧﺮوﺟﯽ، ﻋﻤﻖ ﺟﺮﯾﺎن اﻓﺰاﯾﺶ ﯾﺎﻓﺖ و ﻣﻨﺠﺮ ﺑﻪ ﮐﺎﻫﺶ اﺑﻌﺎد ﻧﺎﺣﯿﻪ ﺟﺪاﺷﺪﮔﯽ ﺷﺪ. ﻣﻄﺎﺑﻖ ﻧﺘﺎﯾﺞ ﻋﺪدي، اﺑﻌﺎد ﻧﺎﺣﯿﻪ ﺟﺪاﺷﺪﮔﯽ در راﺳﺘﺎي ﻗﺎﺋﻢ از ﮐﻒ ﮐﺎﻧﺎل ﺑﻪ ﺳﻄﺢ آب اﻓﺰاﯾﺶ ﯾﺎﻓﺖ، ﺑﻪﻃﻮريﮐﻪ ﺑﺮاي ﻧﺴﺒﺖ دﺑﯽ 0/6و ﻧﺴﺒﺖ ارﺗﻔﺎع ﺳﺮرﯾﺰ 0/377، ﻃﻮل ﻧﺎﺣﯿﻪ ﺟﺪاﺷﺪﮔﯽ در ﮐﻒ ﮐﺎﻧﺎل، ﻓﺎﺻﻠﻪ 0/1ﻣﺘﺮ از ﮐﻒ و در ﺳﻄﺢ آب ﺑﻪ ﺗﺮﺗﯿﺐ در ﺣﺪود 60ﺳﺎﻧﺘﯿﻤﺘﺮ، 75 ﺳﺎﻧﺘﯿﻤﺘﺮ و 85 ﺳﺎﻧﺘﯿﻤﺘﺮ ﺑﻮد. ﺑﻨﺎﺑﺮاﯾﻦ از ﺳﻄﺢ آب ﺑﻪ ﺳﻤﺖ ﮐﻒ ﮐﺎﻧﺎل ﻃﻮل ﻧﺎﺣﯿﻪ ﺟﺪاﺷﺪﮔﯽ در ﺣﺪود 29% ﮐﺎﻫﺶ ﯾﺎﻓﺖ.

Study of separation zone is so important in right-angled three-branch or four-branch open channel junctions. Some effective parameters in this case are inlet discharge ratio and flow depth which in this research the effect of inlet discharge ratio and weir height ratios (flow depth) on flow pattern and dimensions of separation zone has been simulated numerically. Investigation of numerical results showed that k-ω model well validated with experimental results and had good agreement, so that simulation error was less than 20%. Dimensions of separation zone in main and side channels were directly proportional with the inlet discharge ratio. Also as increases of height ratio of outlet weirs, flow depth increases and separation zone dimensions decreased. According to the analysis of numerical results, dimensions of separation zone in vertical direction, of the channel bed to water surface increased, so that for discharge ratio 0.6 and height ratio of outlet weirs 0.377, length of separation zone at the channel bed, 0.1 m up the bed and water surface was about 60 cm, 75 cm and 85 cm, respectively. So of the water surface towards the channel bed, length of separation zone decreased about %29.