شماره ركورد :
1142698
عنوان مقاله :
بررسي مشخصات هيدروليكي جريان در سرريزهاي خط جرياني
عنوان به زبان ديگر :
Hydraulic Characteristics of flow over the streamlined weirs
پديد آورندگان :
باقري، سارا دانشگاه صنعتي اصفهان - دانشكده مهندسي عمران , كبيري ساماني، عبدالرضا دانشگاه صنعتي اصفهان - دانشكده مهندسي عمران
تعداد صفحه :
14
از صفحه :
29
تا صفحه :
42
كليدواژه :
سرريز خط جرياني , تبديل ژوكوفسكي , نرم‌افزار OpenFoam , نيم‌رخ سرعت , توزيع فشار
چكيده فارسي :
هدف از اين تحقيق، مطالعه تحليلي، عددي و آزمايشگاهي جريان بر روي سرريزهاي خط جرياني است. با توجه به اهداف تحقيق و به منظور ارزيابي نتايج مدلسازيهاي عددي حاصل از نرمافزار متنباز OpenFoam، مدلهاي آزمايشگاهي سرريزهاي خط جرياني بر اساس تابع تبديل ژوكوفسكي طراحي و در آزمايشگاه مورد مطالعه قرار گرفتند. با بررسي نتايج مدلهاي آشفتگي متفاوت، مدل k-ω SST به عنوان بهترين مدل آشفتگي، در شبيهسازي جريان عبوري از روي سرريزهاي خط جرياني انتخاب شد. نتايج شبيهسازيهاي عددي بهازاي دبيهاي مختلف و خصوصيات هندسي متفاوت، نشان داد كه با افزايش دبي جريان و نيز افزايش ميزان خروج از مركزيت نسبي در رابطه ژوكوفسكي، سرعت بر روي تاج سرريز خط جرياني افزايش و بهتبع آن فشار در اين محل كاهش مييابد. كمترين فشار در نتيجه بيشترين احتمال وقوع پديده كاويتاسيون مربوط به سرريز تاجدايرهاي (نوعي سرريز خط جرياني با خروج از مركزيت واحد) است. همچنين نتايج نشان داد كه بيشترين تنشهاي برشي بستر و نيروهاي فشاري در پاييندست سرريزهاي تاجدايرهاي رخ ميدهند و در مقايسه با سرريزهاي خط جرياني، بيشترين امكان فرسايش مربوط به پاييندست سرريزهاي تاجدايرهاي است. دليل اين امر وقوع امواج ضربهاي، كاهش عمق و افزايش سرعت جريان در پاييندست سرريزهاي تاجدايرهاي ميباشد. علاوه بر اين، كمترين مقادير تنشهاي برشي بستر در بالادست سازه، مربوط به سرريزهاي تاجدايرهاي است و درنتيجه اين نوع سرريز نسبت به ساير انواع سرريزهاي خط جرياني مستعد رسوب گذاري در بالادست خود ميباشد. لذا براساس نتايج حاصل، بهره گيري از ساير انواع سرريزهاي خط جرياني با انحناي مناسب، ميتواند مشكلات رايج در سرريزهاي تاجدايرهاي را مرتفع سازد.
چكيده لاتين :
The present study is subjected to analytical, numerical, and experimental simulation of hydraulic characteristics of flow over the streamlined weirs. Numerical simulations were performed using an open source software namely OpenFoam. According to the objectives of the present study, to evaluate the results of numerical modeling, experimental investigation was conducted, studying different models of streamlined weirs, experimentally. The profiles of the experimental models as well as the simulated numerical models were designed based on the Joukowsky transform function. By analyzing the results of different turbulence models including standard k-ε model, realized k-ε model, RNG k-ε model, k-ω SST model and Reynolds stress LRR model, the k-ω SST model was chosen as the most accurate numerical turbulence model for the simulation of flow over the streamlined weirs. The results of the numerical simulations for different flow discharges and different geometrical characteristics, indicated that, increasing the flow discharge and the relative eccentricity in Joukowsky transform function, tends to increase the velocity and consequently decrease the pressure over the weir crest. Therefore, the lowest pressure and the most probable potential of cavitation belongs to the circular-crested weirs with λ = 1 and high flow discharges. Furthermore, the results show that the greatest bed shear stresses and the compressive forces occur at the downstream end of the circular-crested weirs, thus the downstream zone of the circular-crested weirs is responsible to large values of bed erosion. This is partly due to formation of shock waves, reduction of the flow depth and enhanced velocity of flow downstream of the circular-crested weirs. Furthermore, the lowest bed shear stresses occur at the upstream end of the circular-crested weirs. Therefore, potential of sedimentation upstream of the circular-crested weirs increases. Accordingly, by employing streamlined weirs with λ< 1, and an appropriate curvature, unfavorable flow conditions would be improved, leading to a more safe and economic hydraulic structure. The present study is subjected to analytical, numerical, and experimental simulation of hydraulic characteristics of flow over the streamlined weirs. Numerical simulations were performed using an open source software namely OpenFoam. According to the objectives of the present study, to evaluate the results of numerical modeling, experimental investigation was conducted, studying different models of streamlined weirs, experimentally. The profiles of the experimental models as well as the simulated numerical models were designed based on the Joukowsky transform function. By analyzing the results of different turbulence models including standard k-ε model, realized k-ε model, RNG k-ε model, k-ω SST model and Reynolds stress LRR model, the k-ω SST model was chosen as the most accurate numerical turbulence model for the simulation of flow over the streamlined weirs. The results of the numerical simulations for different flow discharges and different geometrical characteristics, indicated that, increasing the flow discharge and the relative eccentricity in Joukowsky transform function, tends to increase the velocity and consequently decrease the pressure over the weir crest. Therefore, the lowest pressure and the most probable potential of cavitation belongs to the circular-crested weirs with λ = 1 and high flow discharges. Furthermore, the results show that the greatest bed shear stresses and the compressive forces occur at the downstream end of the circular-crested weirs, thus the downstream zone of the circular-crested weirs is responsible to large values of bed erosion. This is partly due to formation of shock waves, reduction of the flow depth and enhanced velocity of flow downstream of the circular-crested weirs. Furthermore, the lowest bed shear stresses occur at the upstream end of the circular-crested weirs. Therefore, potential of sedimentation upstream of the circular-crested weirs increases. Accordingly, by employing streamlined weirs with λ< 1, and an appropriate curvature, unfavorable flow conditions would be improved, leading to a more safe and economic hydraulic structure.
سال انتشار :
1396
عنوان نشريه :
مهندسي عمران مدرس
فايل PDF :
8115997
لينک به اين مدرک :
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