پديد آورندگان :
تقي زاده، حامد دانشگاه اروميه - دانشكده فني و مهندسي , ارزنلو، ابوالفضل دانشگاه آزاد واحد تهران مركز - دانشكده فني گروه عمران و مدريت ساخت , كاردان، نازيلا دانشگاه شهيد مدني آذربايجان - گروه مهندسي عمران
كليدواژه :
سرريز سهجانبي , عملكرد هيدروليكي , منحني پلكاني , شبيه‌سازي عددي
چكيده فارسي :
سرريزهاي سهجانبي از جمله مجراهاي تخليه كننده سدها بوده كه عليرغم محدوديت‌هاي هيدروليكي، در شرايط خاص توپوگرافي به عنوان بهترين انتخاب مطرح مي‌شوند. سرريزهاي سهجانبي داراي برخي شرايط هيدروليكي نامناسب هستند كه به‌عنوان نمونه مي‌توان به تلاطم و آشفتگي جريان، اتلاف انرژي و نيز وارد آمدن ضربات نوساني شديد آب بر تمامي وجوه سرريز اشاره كرد. در تحقيق حاضر شبيه‌سازي عددي ميدان جريان سه‌بعدي پيرامون سرريز جانبي U شكل و آبپايه واقع در انتهاي كانال جانبي با استفاده از نرم افزار Flow3D مورد توجه قرار گرفته است. در ادامه با پله‌اي نمودن منحني استاندارد سرريز اوجي سه جانبي، ميزان تغيير در عمق جريان و نوسانات فشار ديناميكي در كانال جانبي مورد ارزيابي قرار گرفته است. براي بررسي كمي نوسانات فشار ديناميكي از عدد بدون بعد پارامتر آشفتگي استفاده شده است. نتايج نشان مي‌دهد پلكاني نمودن منحني استاندارد اين نوع سرريز موجب كاهش برخورد سفره‌هاي ريزشي جريان و افزايش عمق جريان در كانال جانبي مي‌گردد. از سويي ديگر تغيير منحني استاندارد، كاهش قابل توجه شدت نوسانات فشار در داخل كانال جانبي را به دنبال دارد.
چكيده لاتين :
Side channel spillways are widely used in dam outlet works for irrigation and drainage networks; and also in water and wastewater facilities. A special type of these spillways is the Three-sided channel spillway in which the flow enters the side channel through both the end and sides of the spillway. There is a variety of names for these spillways, including bathtub spillways, U-shaped spillways, and duckbill spillways. Those are used in situations where a spillway with a long crest is required. In Three-side spillways, the flow enters through a U-shaped weir (in plan) into the side channel that serves to deliver water downstream. The flow in the side channel is a spatially varied flow with increasing discharge and is especially designed with a non-prismatic cross section (increasing bed width along the flow direction) to avoid channel flow effects on influent flows. Several studies have been carried out to gain a clear understanding of the effective factors and the relations dominating the flow in one-sided channels. Few studies have been done on hydraulic performance of Three-sided channel spillways, however, most studies have only focused on specific applications of the situations of these spillways and have aimed at improving the hydraulic performance of flow. Also, in some studies, determining the optimized values of three design parameters; including side channel bed slope, the appropriate elevation, and shape of the end sill for the spillways were investigated and concluded that the effective crest length for two-sided, L-shaped spillways, taking into account the effect of each of the corners of the spillway on reducing crest length. In this study, the three-dimensional flow filed of U-shaped spillway and end-sill of the side channel are simulated using Flow3D and the effect of flow turbulences have been modelled by RNG closure. Comparison of the numerical and experimental results revealed that this model with RNG closure has capable to carefully simulate the turbulence flow field on these structures. The effect of making stepped the ogee profile of the three-sided spillway on flow depth and dynamic pressure fluctuations has been numerically evaluated; the non-dimensional turbulence index has been used to investigate the fluctuations of the dynamic pressure. The results revealed making stepped the ogee profile causes to reduce the encounter of the side overfalls, and to increase the flow depth in the side channel, in which this lead to considerable decrease in pressure fluctuation intensity. Also the results showed that it is better this type of spillways to be designed in low-flow heads, so as to raise discharge. Using long sideling lateral arms will have a positive effect on the discharge coefficient. Finally, in these spillways the flow from their lateral channel is discharged with delay and in high flow rates is immediately submerged due to severe interference of dropping layers of flow. The area that experiences the most reduction in effective length of the spillway is the part that two side arms and the normal part (perpendicular to the central axis of the side channels) are linked together. By reducing this area and having a short connection between them, the effective length reduction can be reduced.
