بررسی آثار دیوارهای هادی جریان بر عملکرد هیدرولیکی ‌سرریزهای کنگره‌ای قوسی

اﺳﺘﻔﺎده از ﺳﺮرﯾﺰﻫﺎی ﮐﻨﮕﺮه ای ﺑﻪ ﻋﻨﻮان ﯾﮏ راه ﻣﺆﺛﺮ و اﻗﺘﺼﺎدی ﺑﺮای اﻓﺰاﯾﺶ ﻇﺮﻓﯿﺖ آﺑﮕﺬری ﻣﻄﺮح اﺳﺖ . ﻗﺮارﮔﯿﺮی ﺳﯿﮑﻞ ﻫﺎی ﺳﺮرﯾﺰ ﮐﻨﮕﺮه ای روی ﻗﻮﺳﯽ از ﯾﮏ داﯾﺮه ﻣﯽ ﺗﻮاﻧﺪ ﺑﻬﺒﻮد ﺟﻬﺖ ﮔﯿﺮی ﺳﯿﮑﻞ ﻫﺎی ﺳﺮرﯾﺰ ﻧﺴﺒﺖ ﺑﻪ ﺟﺮﯾﺎن ورودی و ﻧﯿﺰ اﻓﺰ اﯾﺶ ﻃﻮل ﺗﺎج ﺑﺎزای ﯾﮏ ﻋﺮض ﻣﻌﯿﻦ را ﺳﺒﺐ ﮔﺮدد. اﯾﻦ ﭘﮋوﻫﺶ ﺑﻪ ﺑﺮرﺳﯽ آزﻣﺎﯾﺸﮕﺎﻫﯽ آﺛﺎر دﯾﻮارﻫﺎی ﻫﺎدی ﺟﺮﯾﺎن ﺑﺮ ﻋﻤﻠﮑﺮد ﺳﺮرﯾﺰﻫﺎی ﮐﻨﮕﺮه ای ﻗﻮﺳﯽ ﻣﯽ ﭘﺮدازد ﺿﻤﻦ ﺑﺮرﺳﯽ آﺛﺎر ﭘﺎراﻣﺘﺮﻫﺎی ﻧﺴﺒﺖ ﺑﺎر ﻫﯿﺪروﻟﯿﮑﯽ ﺑﻪ ارﺗﻔﺎع ﺳﺮرﯾﺰ ( ho/p )، زاوﯾﻪ دﯾﻮار ﺟﺎﻧﺒﯽ ﺳﺮر ﯾﺰ(α) و زاوﯾﻪ اﻧﺤﻨﺎ ( θ) ﺑﺮ ﺿﺮ ﯾﺐ آﺑﮕﺬری و ﮐﺎرآﯾﯽ ﺳﺮرﯾﺰﻫﺎی ﮐﻨﮕﺮه ای ﻗﻮﺳﯽ، آﺛﺎر زاوﯾﻪ ﺑﯿﻦ دﯾﻮارﻫﺎی ﻫﺎدی ﺟﺮﯾﺎن (′θ) ﻧﯿﺰ ﺑﺮ اﯾﻦ ﻣﻬﻢ ﻣﻮرد ﺗﺤﻘﯿﻖ ﻗﺮار ﮔﺮﻓﺘﻪ اﺳﺖ. ﻧﺘﺎ ﯾﺞ ﻧﺸﺎن ﻣﯽ دﻫﺪ ﮐﻪ ﻗﻮﺳﯽ ﮐﺮدن ﺳﺮرﯾﺰ ﮐﻨﮕﺮه ای ﻣﯽ ﺗﻮاﻧﺪ ﺑﻬﺒﻮد ﮐﺎرآﯾﯽ آن را ﺳﺒﺐ ﺷﻮد. ﻋﻠﯽ اﯾﺤﺎل ﺑﺎ اﻓﺰاﯾﺶ ﺑﺎر ﻫﯿﺪروﯾﮑﯽ، ﮐﺎرآﯾﯽ ﺳﺮر ﯾﺰﻫﺎی ﮐﻨﮕﺮه ای ﻗﻮﺳﯽ ﮐﺎﻫﺶ ﻣﯽ ﯾﺎﺑﺪ. در ﻣﻘﺎدﯾﺮ ﭘﺎﯾﯿﻦ زاوﯾﻪ اﻧﺤﻨﺎ، اﻧﺘﺨﺎب ﻣﻨﺎﺳﺐ زاوﯾﻪ ﺑﯿﻦ دﯾﻮارﻫﺎی ﻫﺎدی ﺟﺮﯾﺎن ﻣﯽ ﺗﻮاﻧﺪ ﺗﺎ ﺣﺪود 20 درﺻﺪ ﮐﺎرآﯾﯽ ﺳﺮرﯾﺰ را ﺑﻬﺒﻮد ﺑﺨﺸﺪ. ﻟﯿﮑﻦ آﺛﺎر اﯾﻦ ﭘﺎراﻣﺘﺮ در ﻣﻘﺎدﯾﺮ ﺑﺎﻻی زاوﯾﻪ اﻧﺤﻨﺎ ﻗﺎﺑﻞ ﺻﺮف ﻧﻈﺮ ﮐﺮدن اﺳﺖ.

Investigation of Effects of Entrance Channel Walls on the ‎Hydraulic Performance of ‎Arced Labyrinth Weirs

Labyrinth weir is one of the approaches to increase the discharge capacity. An arced lrm;configuration improves the orientation of the labyrinth weir cycles to the approach flow and lrm;increases the weir crest length for a given width. In this study, the effects of the entrance flow lrm;conditions on the hydraulic performance of the arced lrm;labyrinth weirs is studied experimentally. lrm; The effects of the angle between the entrance channel walls ( Theta; prime;) on the discharge coefficient lrm;and the efficiency are investigated for different values of the lrm;headwater ratio (Ho/P), the lrm;downstream sidewall angle ( alpha;), and the weir arc lrm;angle ( Theta;). lrm; Experiments were conducted in a recirculating flume which is 10 m long, 2 m wide, and 0.9 m lrm;deep at Tarbiat Modares University. To simulate the reservoir conditions, a specific setup was lrm;added to the flume, known as the reservoir simulator. The flume was launched from its two ends lrm;by two pipelines. The inflow passes from underneath of the reservoir simulator and enters into it lrm;through a semicircular opening in its horizontal wall. After moving over the horizontal wall, the lrm;flow comes up through the gap between the vertical wall. Finally, it flows on the platform and lrm;moves towards the downstream channel. All the plates (including the platform and the simulator lrm;walls) have a semicircular planview with a porosity equal to zero. The weirs were mounted on lrm;the platform at the entrance of the downstream channel. Totally 132 experiments were lrm;conducted to investigate the effects of the mentioned parameters on hydraulic performance of lrm;arced labyrinth weirs. lrm; Due to the nappe interference, the local submergence forms in the downstream of the lrm;labyrinth lrm;weirs. The size lrm; of local submergence regions increase by increasing the lrm;headwater ratio lrm;and the arc angle. However, vice versa trend occurs with the downstream sidewall angle. In lrm;addition, for low values of the arc angle, the lateral flow from the side cycles to their adjacent lrm;cycles produces the surface turbulences. The results lrm;indicate that the discharge coefficient lrm;decreases by increasing the lrm;headwater ratio and the downstream sidewall angle. For low values lrm;of the lrm;headwater ratio, the discharge coefficient increases when the arc angle increases. lrm;However, a decreasing trend is observed in high head conditions. By increasing the lrm;arc angle lrm;and decreasing the downstream sidewall angle, the efficiency of a labyrinth weir can be lrm;increased. However, the efficiency gains diminish by increasing the lrm;headwater ratio. lrm; The efficiency of a labyrinth weir can slightly be increased by projecting of the cycles into a lrm;reservoir for low values of Ho/P, alpha;, and Theta;. However, in the wide range of the research domain, lrm;the efficiency decreases when the angle between the entrance channel walls increases. lrm;According to the results of this research, the efficiency of a labyrinth weir can be increased up lrm;to 20% by channelizing abutments in high head conditions. However, the effect of Theta; prime; is lrm;insignificant for higher values of Theta;. In addition, as alpha; decreases, the benefits and the losses of lrm;decreasing Theta; prime; become more lrm;severe at higher and lower values of Ho/P, respectively. lrm;