ارزیابی هیدرولیکی آبگیری جانبی با لوله از کانال با استفاده از مدل عددی

آبگیر جانبی با لوله نوعی سازه هیدرولیکی است که در آبگیری از رودخانه ها و کانال های انتقال آب در مناطقی که توپوگرافی امکان احداث کانال جهت آبگیری را فراهم نمی سازد، به کار برده می شود. در مطالعه حاضر به بررسی عددی برخی از پارامترهای موثر بر راندمان آبگیری جانبی با لوله در یک کانال مستقیم روباز با استفاده از نرم‌افزار flow3d پرداخته شده است. این پارامترها در سه گروه، شامل جهت قرارگیری لوله آبگیر نسبت به راستای جریان اصلی، خصوصیات دهانه لوله آبگیر و نیز موقعیت قرارگیری دهانه لوله آبگیر در نظر گرفته شده است. بررسی ها نشان داد که جریان انحرافی با تغییر خصوصیات دهانه لوله آبگیر، بسته به زاویه آبگیری رفتار متفاوتی را از خود نشان خواهد داد. مشاهدات نشان داد در حالتی که فرورفتگی لوله آبگیر تا حداکثر 40 درصد عرض کانال اصلی باشد و آبگیری از تراز نسبی ارتفاعی 0.28 تا 0.57 عمق آب نسبت به کف کانال انجام شود، آبگیری راندمان قابل قبولی خواهد داشت. زمانی که لوله آبگیر در نزدیکی سطح جریان قرار می گیرد ضریب پادرسوبی (λ) بهترین مقدار را خواهد داشت، هر چند که در این شرایط لوله آبگیر بیشتر در معرض نوسانات سطح جریان قرار دارد و ممکن است باعث بروز مشکلات اجرایی در آبگیری شود.   

hydraulic assessment of pipe lateral intake from openchannel by numerical simulation

intake of water from rivers has recently become a major subject of study in hydraulic projects, such as watertransfer systems and power plants. intake from water resources can be carried out by different methods.lateral intake is influenced by various factors, such as topographic conditions, type of the river, and the plantarget and water conveyance system is a common method using an ope n channel or a pipe. because of various conditions in different regions, a general recommendation for selecting the intake method for all regions cannot be a robust solution; therefore, it is necessary to select suitable lateral intake by extensive and accurate studies and consider the conditions technically and economically. lateral intake which uses a pipe is a hydraulic structure that has been utilized in water intake from rivers and channels, especially in those situations in which the area topography do not allows to build a lateral channel for water intake. there have been few studies conducted on the above mentioned structures and that what is the optimal condition in water intake using a pipe still have not really characterized. this study deals with the numerical investigation of effective geometrical parameters on lateral intake efficiency with a pipe in an outdoor direct rectangular channel by using software flow3d. the parameters categorize into three group including the direction of the pipe intake aligning with the current, the characteristics of pipe intake opening, and also the position of pipe intake opening. the results show that among different angles of the intake, the 90-degree angle divert the highest discharge; because it has more pressure gradient difference than the others. increasing the discharge leads to diverted sediment increase to lateral intake. for this purpose, at 90-degree angle the highest sediment divert to the pipe happens. since the criterion of choosing the best angle intake is anti-sediment coefficient. comparing the anti sediment coefficient among different angles showed that the 90-degree angle has the best efficiency of intake. also an analogy of diverted discharge results for different levels of pipeintake indicated that if the water intake happens at relative height level of 0.28 to 0.57, the diverted discharge would be more than the simulated case. furthermore, by comparing anti-sediment coefficient for different levels demonstrate that if the pipe intake locates near the surface of current, anti-sediment coefficient will have an acceptable value. hence, results of diverted discharge at different depressions pipe intakedemonstrate that the less the rate of pipe intake depression, the more discharge will be diverted. also an analogy of anti-sediment coefficients at 45 and 90-degree angle show that the influence of pipe intakedepression on intake efficiency change when affected by angle intake. so, finally results indicate that divertflow, when the characteristics of intake opening change, depend on angle intake would show a different behavior himself. as regards to optimum location of the intake, it was observed that location of the pipe intake inlet in almost 40% of the main channel width could yield a quite acceptable performance for the pipe. furthermore, location of the pipe intake near the free surface could yield a high performance of the pipe intake as a result of low sediment concentration and high flow velocity. however, it should be considered that near the free surface, wavy flow and water surface fluctuations can influence the intake performance.