شبیه‌سازی عددی الگوی جریان پیرامون پایه پل منفرد با حضور صفحات مستغرق بالادستی مستقر در قوس 180 درجه تند با بستر آبرفتی تحت تاثیر فاصله صفحات مستغرق از هم و پایه پل

در این پژوهش از مدل عددی  ssiimبرای بررسی الگوی جریان، کانتورهایی سرعت، قدرت جریان و پارامترهای آشفتگی در اطراف پایه  پل عمودی با حضور صفحات مستغرق با طول هم پوشانی مختلف، و قرارگیری صفحات مستغرق از پایه ی پل و از یکدیگر در شش  فاصله مختلف، در قوس 180 درجه تند استفاده گردید و مقایسه نتایج تحلیل عددی و آزمایشگاهی انجام شد. تطابق داده های عددی و آزمایشگاهی بیانگر عملکرد مناسب مدل عددی ssiim  در مدل‌سازی الگوی جریان در مسئله مورد بررسی می باشد. نتایج تحقیق نشان داد که محدوده ی قدرت جریان ثانویه، در تمامی مدل های با حضور صفحات مستغرق از 10/5 تا 12 درصد اندازه گیری شد. در حالتی که صفحات مستغرق هم پوشانی با هم نداشتند و استقرار صفحات مستغرق در فاصله ی 2/5برابر قطر پایه از پایه و فاصله معادل 2 برابر قطر پایه از همدیگر و در بالادست پایه بوده کمترین مقدار و در حالت هم پوشانی 100 درصد صفحات، در آرایش استقرار صفحات مستغرق در فاصله 5 برابر قطر پایه از آن و فاصله 2 برابر قطر پایه از همدیگر و در بالادست پایه بیشترین مقدار خود را داشته است. همچنین تغییرات تنش برشی بعد از ایجاد آبشستگی موضعی محاسبه شد. تنش برشی ماکزیمم از ابتدای قوس تا نزدیکی خروجی قوس به سمت جداره داخلی قوس متمایل بود و در محدوده خروجی قوس تنش برشی ماکزیمم به سمت میانه قوس و سپس نیمه ی دوم قوس منتقل گردید.

numerical simulation of the flow pattern around a single bridge pier with upstream of submerged vanes in sharp 180 degree bend with an alluvial bed under the influence of submerged vanes and the bridge pier

in this research, the ssiim numerical model is investigated to investigate the flow pattern, velocity meters, current strength and turbulence parameters around the pier of the vertical bridge with submerged vanes. the parameters of different overlap length, and the distance of the submerged vanes upstream from the pier of the bridge and from each other in sharp 180 degree bend in the steep ratio hydraulic radius 2 with a height of 90 cm and a width of 100 cm and a length of straight direction upstream and downstream of the bend respectively 6.5 m and 5 m, were analyzed. ssiim software was used to investigate the flow field around the around the cylindrical bridge pier and upstream submerged vanes. the k ε turbulence model was also used to solve the navier stokes equations. in order to validate, the results of the simulated model were compared with the available experimental data in the case of submerged vanes located upstream of the bridge pier. the match between the numerical and experimental data indicated the proper performance of the ssiim numerical model in modeling the flow pattern in the problem under study. the results showed that the range of secondary flow power was measured in all models with the presence of upstream submerged vanes from 10.5 to 12%. in the case where the submerged vanes did not overlap with each other and the placement of the submerged vanes at a distance of 2.5 times the pier diameter from the pier and a distance equal to 2 times the pier diameter from each other and above the pier is the lowest value and in the overlapping state 100 percentage of vanes, in the arrangement of submerged vanes at a distance of 5 times the pier diameter and 2 times the pier diameter of each other and above the pier has its highest value. shear stress changes after local scouring were also calculated. the maximum shear stress from the beginning of the bend to near the bend exit was inclined towards the inner bank of the bend and in the bend output range the maximum shear stress was transferred to the middle of the bend and then the second half of the bend. the results also showed that the tangential velocity was increased as the immersion range of the submerged vanes and the pier approached, so that the maximum tangential velocity occurred in the passage through the pier. as the height from the initial bed increases, the maximum positive tangential velocities increase. the results also showed that at the level near the bed, the radial flow is towards the inner bank. the greatest difference in radial velocities, as opposed to tangential velocities, is observed near the bed. the highest changes in the maximum landing number are related to models with submerged vanes at a distance of 7.5 times the pier diameter, which by changing the distance between the vanes from 1 to 1.5 times the pier diameter from each other, an increase of 12.5% and by changing the distance of the submerged vanes to 2 times the pier diameter from each other, it decreases by 11%.