1دانشجوی کارشناسی ارشد سازه های آبی گروه مهندسی آب، دانشکده کشاورزی دانشگاه ارومیه
2استادیار دانشگاه ارومیه
چکیده
دینامیک جریان در محل تلاقی رودخانه‌ها با شش ناحیۀ اصلی قابل تشخیص است: ناحیۀ رکود جریان، انحراف جریان، جدایی جریان، حداکثر سرعت، بازیافت جریان و لایه‌های برشی. زاویۀ تلاقی، نسبت دبی بین دو شاخه، اختلاف رقوم و غیره از جمله پارامترهای تاثیرگذار بر ابعاد این نواحی هستند. توجه بیشتر مطالعات قبلی بر تلاقی کانال‌های همکف معطوف بوده است؛ و در زمینۀ تلاقی‌های غیرهمکف مطالعات اندک است. این تحقیق به ارزیابی اثر زاویۀ تلاقی دو کانال بر دینامیک جریان (ناحیۀ جداشدگی، الگوی جریان و تراز آب)، با استفاده از شبیه‌سازی سه‌بعدی Flow-3D در تلاقی‌های همکف و غیرهمکف می‌پردازد. فاکتورهای مهم بررسی شده در این تحقیق، چهار نسبت دبی (نسبت دبی شاخۀ فرعی به دبی کل برابر با 2/0، 33/0، 5/0 و 67/0)، سه زاویه (45، 60 و 90 درجه) و اختلاف رقوم‌های متغیر هستند. پیش‌بینی‌های شبیه‌سازی عددی تطابق خوبی با نتایج آزمایشگاهی دارد. نتایج تحقیق حاضر نشان می‌دهد که بین دینامیک جریان در تلاقی‌های همکف و غیرهمکف تفاوت زیاد است و زاویۀ اتصال نقشی مهم در تلاقی رودخانه‌ها، به‌ویژه در تلاقی‌های همکف بازی می‌کند. با افزایش زاویه، ابعاد ناحیۀ جداشدگی جریان افزایش می‌یابد به‌طوری‌که طول ناحیۀ جداشدگی در زاویۀ 90 درجه 3/2 برابر طول ناحیۀ جداشدگی در زاویۀ 45 درجه برای تلاقی‌های همکف است. این مقدار در تلاقی‌های غیرهمکف با اختلاف رقوم‌های نسبی برابر با 1/0، 2/0 و 3/0 به‌ترتیب برابر با 5/4، 3 و 1/2 است.
Numerical iInvestigation of the Effect of Junction Angle on Flow Dynamic at the Canal Junction of Concordance and
Discordance Bed Level
نویسندگان [English]
Tohid Aghazade1؛
چکیده [English]
Flow dynamics at river confluences can be characterized by six major regions of flow stagnation, flow deflection, flow separation, maximum velocity, flow recovery and distinct shear layers. The junction angle, discharge ratio channels and bed elevation differences are the parameters that affect the magnitude of these regions. Most of previous studies have paid attention to the concordance canal confluences, but few studies have been conducted on the bed discordance confluences. This study investigates the effect of junction angles on flow dynamics (separation zone, flow patternsand water level) in concordance and discordance bed levels of confluences by using a 3-D numerical model (Flow-3D). Important factors that are considered in this study are the four discharge ratios (ratio of tributary channel discharge to total discharge equal to 0.2, 0.33, 0.5 and 0.67), three angles (45, 60 and 90 degree) and variable river bed levels. The numerical simulation results showed good agreement with the experimental results. The results indicated that there are a lot of differences between dynamic of confluences with concordance and discordance bed levels and the junction angle plays an important role at the river confluences, especially in bed concordance junctions. Also as the angle increases, the flow separation zone dimensions increases; in such a way the separation zone length at 90 degree angle was 2.3 times of 45 degree in concordance bed level. Finally the value in case of relative bed discordance levels of 0.1, 0.2 and 0.33 were found to be 4.5, 3 and 2.1, respectively.
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