بررسی عددی تاثیر تعداد سازه بافل بر راندمان حوضچه ته‌نشینی اولیه در ابعاد واقعی

نویسندگان
محمد جوادی راد 1
مهدی شاهرخی 2
طاهر رجایی 3
1 - دانشگاه قم
2 گروه مهندسی عمران- دانشگاه غیاث الدین
3 دانشیار گروه مهندسی عمران- دانشگاه قم
چکیده
حوضچه‌های ته‌نشینی از مهم‌ترین اجزای تصفیه‌خانه‌های فاضلاب هستند بطوریکه حدود یک سوم هزینه احداث تصفیه‌خانه‌های فاضلاب به ساخت حوضچه‌ها مربوط می‌شود. در تحقیق حاضر اثر سازه بافل بر راندمان هیدرولیکی حوضچه‌های ته‌نشینی اولیه بوسیله مدلسازی عددی سه بعدی در نرم افزار Flow-3D بررسی شده‌است. حوضچه ته‌نشینی در ابعاد واقعی و مدل ساده شده حوضچه ته‌نشینی اولیه مستطیلی تصفیه‌خانه فاضلاب جنوب تهران می‌باشد. در مدلسازی عددی بر اساس انطباق نتایج عددی با داده‌های آزمایشگاهی، برای حل آشفتگی جریان از مدل آشفتگی و برای حل فشار از روش GMRES استفاده شده‌است. صحت‌سنجی نتایج شبیه‌سازی عددی با داده‌های آزمایشگاهی پیشین با دقت مناسبی اطمینان نتایج عددی را تصدیق می‌کند. محل بهینه بافل اول از تحقیقات قبلی نویسندگان مشخص است. برای تعیین تعداد بهینه بافل‌ها، مقایسه نتایج بین حوضچه بدون بافل و حالت‌های بهینه حوضچه یک، دو و سه بافل انجام شد. نتایج نشان می‌دهد که وجود سازه بافل سبب جلوگیری از جت جریان در کف و افزایش راندمان رسوبگذاری حوضچه‌های ته‌نشینی اولیه می‌شود. به‌علاوه با اضافه کردن یک بافل در موقعیت مناسب، بزرگی سرعت ماکزیمم، حجم ناحیه چرخشی و انرژی جنبشی کاهش می‌یابد بطوریکه با اضافه کردن بافل اول، دوم و سوم بترتیب حجم ناحیه چرخشی نسبت به حالت بدون بافل 13/4، 44/4 و 63/4 درصد کاهش می‌یابد. همچنین مقایسه منحنی‌های FTC برای حالت‌های تعداد مختلف بافل و بدون‌بافل بهبود راندمان رسوبگذاری با افزایش تعداد بافل را نشان می‌دهد.

کلیدواژه‌ها

موضوعات

عنوان مقاله English

Numerical Investigation of the number of baffles effect on the efficiency of primary sedimentation tank in true dimensions

نویسندگان English

mohammad javadi rad 1
mahdi shahrokhi 2
taher rajaee 3
2 Assistant Prof. of Department of Civil Engineering, Ghyasedin University
3 Associate Prof. of Department of Civil Engineering, Qom University
چکیده English

Numerical Investigation of the number of baffles effect on the efficiency of primary sedimentation tank in true dimensions.

Settling tanks of wastewater treatment plants are the most important components so that about one-third of the cost of a wastewater treatment plant construction is concerned to these tanks. In addition, the regulations referred to design of settling tanks are not enough. According to these, the adverse factors in settling tanks is very important to design and improve their performance. These factors in primary sedimentation tanks are including circulation zones, the phenomenon of short circuiting and non-uniform flow. One of the most important ways to improve flow conditions and increase the efficiency of settling tanks, is modifying the geometry of the tank through the installation of baffles. In this investigation, the effect of baffle structures on the hydraulic efficiency of primary sedimentation tanks has been investigated by three-dimensional numerical modeling in Flow-3D software. In this study, the optimum number of baffles is studied to increase hydraulic efficiency. Settling tank in true size and simplified model primary settling tank treatment plant south of Tehran. The geometry Specifications of tank include of length tank (L) from the main inlet to the overflow output of 60 m, a width of tank (W) 12.9 m, water depth in normal mode (H) 3 m. the input flow rate to the tank 650 l/s. Model geometry using AutoCAD software and three-dimensional shape is drawn. In this study, from three mesh blocks to mesh geometry model is used. All three of these blocks in all directions are fully in touch with and the type of are linked blocks. Intended for three blocks, the size of the mesh is selected respectively, 5, 7 and 10 cm monotonically in each direction. In numerical modeling, the turbulence model used to solve turbulent flow and to solve pressure the GMRES method is used. In addition, the VOF technique to show the behavior of fluid on free surface flow and FAVOR technique have been used to simulate surfaces and geometric boundaries. Verification of numerical simulation results with former experimental data properly acknowledges the numerical results. It is already known the optimal location of the first baffle.

The results show that baffle causes the uniformity flow and increase removal efficiency of the primary sedimentation tanks. To determine the optimum number of baffles, the comparison results between no baffle tank and optimized cases with one, two and three baffle done. Using more baffles, in ideal conditions, causes suppression of the jet flow and more chances the suspended particles deposition. The addition of new baffles in suitable locations reduces the maximum velocity amount, the size of the circulation zones and kinetic energy and create uniform velocity vectors inside the settling zone. Volume circulation zones by using one, two and three baffles compared to non-baffle decreased 4.18, 4.44 and 4.56% of the total tank volume, respectively. Finally, the results of the FTC method for several cases indicated that using number of baffles lead to increasing the performance of the sedimentation tanks.

کلیدواژه‌ها English

Flow-3D
primary settling tanks
baffle
hydraulic efficiency
sedimentation
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مهندسی عمران مدرس
دوره 17، شماره 5
آذر و دی 1396
صفحه 49-59