پديد آورندگان :
ﻋﻠﯿﭙﻮر، ﺳﻬﯿﻼ داﻧﺸﮕﺎه اروﻣﯿﻪ - گروه ﻣﻬﻨﺪﺳﯽ آب , ﺑﻬﻤﻨﺶ، جواد داﻧﺸﮕﺎه اروﻣﯿﻪ - گروه ﻣﻬﻨﺪﺳﯽ آب , نيك پور، محمدرضا داﻧﺸﮕﺎه محقق اردبيلي - گروه ﻣﻬﻨﺪﺳﯽ آب
كليدواژه :
اﻣﻮاج ﺿﺮﺑﻪاي , ﺗﺒﺪﯾﻞ ﻫﻤﮕﺮا , زاوﯾﻪ ﺷﯿﺐ ﺟﺎﻧﺒﯽ , ﺟﺮﯾﺎن ﻓﻮق ﺑﺤﺮاﻧﯽ , ﻃﻮل ﻣﻮرب
چكيده فارسي :
ﺳﺎﺑﻘﻪ و ﻫﺪف: ﺗﺒﺪﯾﻞﻫﺎي ﻫﻤﮕﺮا در ﺟﺮﯾﺎنﻫﺎي ﻓﻮق ﺑﺤﺮاﻧﯽ ﮐﺎرﺑﺮدﻫﺎي ﮔﺴﺘﺮدهاي دارﻧﺪ .از ﺟﻤﻠﻪ آن ﻣﯽﺗﻮان ﺑﻪ اﻧﺘﻘﺎل ﺟﺮﯾﺎن از ﮐﺎﻧﺎلﻫﺎي آﺑﮕﯿﺮ ﺳﺪﻫﺎ ﺑﻪ ﺳﺮرﯾﺰﻫﺎي ﺗﻮﻧﻠﯽ، ﮐﺎﻫﺶ ﻋﺮض ﮐﺎﻧﺎل در ﺗﻨﺪآبﻫﺎ و ﮐﺎﻫﺶ زﻣﺎن اﻧﺘﻘﺎل ﺟﺮﯾﺎن در ﮐﺎﻧﺎلﻫﺎي اﻧﺘﻘﺎل ﺳﯿﻼب اﺷﺎره ﮐﺮد .در ﻣﻄﺎﻟﻌﻪ ﺟﺮﯾﺎنﻫﺎي ﻓﻮق ﺑﺤﺮاﻧﯽ ﺗﺸﮑﯿﻞ اﻣﻮاج ﺿﺮﺑﻪاي از اﻫﻤﯿﺖ ﺑﺎﻻﯾﯽ ﺑﺮﺧﻮردار اﺳﺖ .ﺗﻮﻟﯿﺪ و ﺗﻮﺳﻌﻪ اﯾﻦ اﻣﻮاج ﺑﻪ دﻟﯿﻞ اﻓﺰاﯾﺶ ارﺗﻔﺎع آب ﺑﻪ اﻧﺪازه ﭼﻨﺪﯾﻦ ﺑﺮاﺑﺮ ﻋﻤﻖ ﺟﺮﯾﺎن ورودي و ﮔﺴﺘﺮش آن در ﻣﺤﺪوده وﺳﯿﻌﯽ از ﮐﺎﻧﺎل ﭘﺎﯾﯿﻦ دﺳﺖ و ﻧﺎﻫﻤﻮار ﺳﺎﺧﺘﻦ ﺳﻄﺢ آب ﺑﻪ ﻟﺤﺎظ ﻣﻬﻨﺪﺳﯽ ﻧﺎﻣﻄﻠﻮب ﺑﻮده و ﻫﺮ ﮔﻮﻧﻪ ﻃﺮاﺣﯽ ﺿﻌﯿﻒ ﮐﺎﻧﺎل ﻣﯽﺗﻮاﻧﺪ ﻣﻨﺠﺮ ﺑﻪ آﺑﺸﺴﺘﮕﯽ دﯾﻮارهﻫﺎ و ﮐﻒ ﮐﺎﻧﺎل، آﺳﯿﺐ رﺳﺎﻧﺪن ﺑﻪ ﺗﺠﻬﯿﺰات در ﻣﺴﯿﺮ ﺟﺮﯾﺎن و ﺑﺎﻻ ﺑﺮدن ﻫﺰﯾﻨﻪﻫﺎي ﻣﺮﺑﻮط ﺑﻪ ﻧﮕﻬﺪاري و ﮐﺎﻫﺶ راﻧﺪﻣﺎن اﻧﺘﻘﺎل آب ﮔﺮدد .در ﭘﮋوﻫﺶ ﺣﺎﺿﺮ ﺗﺸﮑﯿﻞ اﻣﻮاج ﺿﺮﺑﻪ اي در ﺗﺒﺪﯾﻞﻫﺎي ﻫﻤﮕﺮاي ﮐﺎﻧﺎل روﺑﺎز ﺑﺎ ﻣﻘﺎﻃﻊ ذوزﻧﻘﻪاي و ﻣﺴﺘﻄﯿﻠﯽ ﺑﺎ ﺑﻪ ﮐﺎرﮔﯿﺮي ﻣﺪلﻫﺎي آزﻣﺎﯾﺸﮕﺎﻫﯽ ﻣﻮرد ﺑﺮرﺳﯽ ﻗﺮار ﮔﺮﻓﺖ.
ﻣﻮاد و روش ﻫﺎ: ﺑﻪ ﻣﻨﻈﻮر ﺑﺮرﺳﯽ ﭘﺎراﻣﺘﺮﻫﺎي ﻫﯿﺪروﻟﯿﮑﯽ اﻣﻮاج ﺿﺮﺑﻪ اي در ﺗﺒﺪﯾﻞﻫﺎي ﻫﻤﮕﺮا، دوازده ﻣﺪل ﺑﺎ ﻫﻨﺪﺳﻪ ﻫﺎي ﻣﺘﻔﺎوت به كار گرفته شد.ﻃﻮل ﻣﻮرب دﯾﻮارهﻫﺎي ﺗﺒﺪﯾﻞ (0/5، 0/75و 1متر)و زاوﯾﻪ ﺷﯿﺐ ﺟﺎﻧﺒﯽ دﯾﻮارهﻫﺎ (90،60،45،33/69 درجه) متغيرهاي هندسي ﻣﻮرد ﻣﻄﺎﻟﻌﻪ در ﭘﮋوﻫﺶ ﺣﺎﺿﺮ ﺑﻮد .ﻣﻘﺪار ﻧﺴﺒﺖ ﻫﻤﮕﺮاﯾﯽ در ﻫﻤﻪ مدل ها ي ﻣﺬﮐﻮر ﺑﻪ ازاي چهار عدد فرود مختلف درمحدوده 9/23 -3/25 اندازه گيري شد.
ﯾﺎﻓﺘﻪ ﻫﺎ: ﻣﻘﺎدﯾﺮ اﻧﺪازهﮔﯿﺮي ﺷﺪه در ﺗﺒﺪﯾﻞﻫﺎي ﻫﻤﮕﺮا ﺑﯿﺎﻧﮕﺮ ﺗﻮزﯾﻊ ﻏﯿﺮﯾﮑﻨﻮاﺧﺖ ﺳﺮﻋﺖ در راﺳﺘﺎي ﻗﺎﺋﻢ اﻣﻮاج ﺿﺮﺑﻪ اي ﺑﻮد .ﻫﻤﭽﻨﯿﻦ ﺣﺮﮐﺖ ﺟﺒﻬﻪ ﻣﻮج ﺑﻪ ﺳﻤﺖ ﭘﺎﯾﯿﻦدﺳﺖ ﺑﺎ ﮐﺎﻫﺶ ﺳﺮﻋﺖ و اﻓﺰاﯾﺶ ارﺗﻔﺎع ﻣﻮج ﻫﻤﺮاه ﺑﻮد ﮐﻪ ﺑﻪ ازاي ﻫﻨﺪﺳﻪﻫﺎي ﻣﺨﺘﻠﻒ ﺗﺒﺪﯾﻞ، روﻧﺪ ﺗﻐﯿﯿﺮات ﻣﺬﮐﻮر ﻧﯿﺰ ﻣﺘﻔﺎوت ﺑﻮد .ﻧﺘﺎﯾﺞ ﻧﺸﺎن داد ﺣﺪاﮐﺜﺮ ارﺗﻔﺎع اﻣﻮاج ﺿﺮﺑﻪ اي در ﺗﺒﺪﯾﻞﻫﺎي ﻫﻤﮕﺮا ﺑﺎ ﻣﻘﺎﻃﻊ ذوزﻧﻘﻪاي ﺑﻪ زواياي شيب جانبي 33/69، 45و60
درﺟﻪ ﻧﺴﺒﺖ ﺑﻪ ﻣﻘﺎﻃﻊ مستطيلي ﻪ ﻃﻮر ﻣﯿﺎﻧﮕﯿﻦ، ﺑﻪ ﺗﺮﺗﯿﺐ به ميزان 64/8، 54/3 و 39/6 درصد كاهش يافت .همچنين حداكثر سرعت ضربه اي در ﺗﺒﺪﯾﻞ ﻫﺎي ﻫﻤﮕﺮا ﺑﺎ ﻣﻘﺎﻃﻊ ذوزﻧﻘﻪاي ﺑﻪ ازاي زواﯾﺎي ﺷﯿﺐ ﺟﺎﻧﺒﯽ ﻣﺬﮐﻮر ﻧﺴﺒﺖ ﺑﻪ ﻣﻘﺎﻃﻊ ﻣﺴﺘﻄﯿﻠﯽ ﺑﻪﻃﻮر ميانگين ، به ترتيب به ميزان 39/1،31/6و16/5 درصدكاهش يافت .به ازاي فرود ثابت و ﻃﻮل ﯾﮑﺴﺎن دﯾﻮاره ﺗﺒﺪﯾﻞ، اﻓﺰاﯾﺶ زاوﯾﻪ ﺷﯿﺐ ﺟﺎﻧﺒﯽ ﺑﺎ اﻓﺰاﯾﺶ اﺳﺘﻬﻼك اﻧﺮژي اﻣﻮاج ﺿﺮﺑﻪاي ﻫﻤﺮاه ﺑﻮد .ﻫﻤﭽﻨﯿﻦ ﺑﯿﺶ ﺗﺮﯾﻦ نرخ استهلاك انرژي اﻣﻮاج ﺿﺮﺑﻪاي ﻫﻤﺮاه ﺑﻮد .ﻫﻤﭽﻨﯿﻦ ﺑﯿﺶ ﺗﺮﯾﻦ نرخ استهلاك انرژي درﻃﻮل دﯾﻮاره 0/5 مشاهده شد . .ﺑﻪﻃﻮريﮐﻪ ﻣﻘﺎدﯾﺮ اﻓﺖ اﻧﺮژي اﻣﻮاج ضربه اي به ازاي طول ديواره ي مذكور ،عدد فرود 7/26 و زواياي شيب جانبي
90،60،45،33/69 درجه به ترتيب برابر 16/39 ، 15/43، 14/69 و 18/72 درصد بدست آمد.
نتيجه ﮔﯿﺮي: ﺗﺤﻠﯿﻞ ﭘﺮوﻓﯿﻞﻫﺎي ﺳﺮﻋﺖ و ﺳﻄﺢ آزاد اﻣﻮاج ﺿﺮﺑﻪاي ﺑﯿﺎﻧﮕﺮ آن ﺑﻮد ﮐﻪ در ﺣﺎﻟﺖ ﮐﻠﯽ ﮐﺎﻫﺶ زاوﯾﻪ ﺷﯿﺐ ﺟﺎﻧﺒﯽ )اﻓﺰاﯾﺶ ﺷﯿﺐ ﺟﺎﻧﺒﯽ (دﯾﻮاره ﺗﺒﺪﯾﻞ، اﻓﺰاﯾﺶ ﻃﻮل ﻣﻮرب دﯾﻮاره ﺗﺒﺪﯾﻞ و ﻫﻤﭽﻨﯿﻦ ﮐﺎﻫﺶ ﻋﺪد ﻓﺮود ﺟﺮﯾﺎن راﺑﻄﻪ ﻣﺴﺘﻘﯿﻢ ﺑﺎ ﮐﺎﻫﺶ ارﺗﻔﺎع و ﺳﺮﻋﺖ اﻣﻮاج دارد .ﻧﻈﺮ ﺑﻪ اﯾﻦ ﮐﻪ ﮐﺎﻧﺎلﻫﺎي اﺟﺮاﯾﯽ ﻋﻤﺪﺗﺎً ﺑﺎ ﻣﻘﻄﻊ ذوزﻧﻘﻪاي ﺳﺎﺧﺘﻪ و ﺑﻬﺮه ﺑﺮداري ﻣﯽﺷﻮﻧﺪ، ﯾﺎﻓﺘﻪﻫﺎي ﭘﮋوﻫﺶ ﺣﺎﺿﺮ ﺑﺮاي ﻣﻬﻨﺪﺳﯿﻦ ﻃﺮاح ﻣﯽﺗﻮاﻧﺪ ﺑﺴﯿﺎر ﺳﻮدﻣﻨﺪ ﺑﺎﺷﺪ.
چكيده لاتين :
Background and Objectives: Contractions have many uses in supercritical flows, such as flow conveyance from intake channels of dams to tunnel spillways, reduction of chutes width and reduction of flow conveyance time in the flood conduits. In supercritical flows studies, the formation of the shock waves has an important role. Technically, production and development of the mentioned waves are undesirable due to water depth increase because of several times increasing of inflow water depth, its spread at a wide range in downstream of channel and water surface roughness. Any weak design of channels under supercritical condition can cause to scour channel’s bed and walls, damage to equipment in the flow direction, raising maintenance costs and reduce water conveyance efficiency. In the present research, the formation of shock waves in converged transitions of open channel with rectangular and trapezoidal sections was investigated using laboratory and physical models.
Materials and Methods: In order to investigate hydraulic parameters of shock waves in the converged transitions, twelve models with different geometries were used. In the present research, the studied geometric variables were the diagonal length of transition walls (0.5, 0.75 and 1 m) and side wall angle (33.69º, 45º, 60º and 90º). In all used models, the convergence ratio was 0.5. The height and instantaneous velocity were measured in different points of formed shock waves in the mentioned models for four different Froude number in the range of 3.25 to 9.23.
Results: The measured values in the converged transitions showed that the velocity distribution was not uniform in the vertical direction of shock waves. Also, the results showed that by traveling wave front toward downstream cause to reduce wave velocity and increase wave height so that for various geometries, the changes trend was different. The results showed that on average, and for side slopes angels of 33.69º, 45º and 60º, the maximum height of shock waves was reduced 64.8%, 54.3% and 39.6% respectively in the comparison of trapezoidal and rectangular sections. Also, in the converged transitions and for the mentioned side slope angles, maximum shock wave velocity was reduced 39.1%, 31.6% and 16.5% respectively in the comparison of trapezoidal and rectangular sections. Increasing of side slope angle was accompanied with energy dissipation increment of shock waves for a constant Froude number and transition wall length. Also, maximum value of energy dissipation was seen for 0.5 m of wall length. The values of energy dissipation for the mentioned length, Fr1=7.26 and side slopes angels of 33.69º, 45º, 60º and 90º were achieved 14.69%, 15.43%, 16.34% and 18.72%, respectively.
Conclusion: The analysis of the velocity profiles and free surface of shock waves showed that in general the reduction of side slope angle (increasing side slopes) of the transition wall, increase of diagonal wall length of the transition and reduction of Froude number have a direct relationship with the reduction of waves velocity and height. Since channels are constructed in the form of trapezoidal, the obtained results of the present research can be very useful for designer engineers.
