نوع مقاله: مقاله پژوهشی
نویسندگان
1 دانشجوی دکترا، دانشگاه فردوسی مشهد، گروه مهندسی آب– سازههای آبی.
2 دانشیار دانشگاه فردوسی مشهد، دانشکده کشاورزی، گروه مهندسی آب
3 استاد دانشگاه فردوسی مشهد، دانشکده کشاورزی، گروه مهندسی آب.
چکیده
حفاظت از خطوط لوله انتقال َآب- فاضلاب و یا مواد سوختی، روی بستر فرسایشی دریا و رودخانهها در برابر عواملی چون خمش، لغزش و حتی شکستگی از مسائل مهم و پرهزینه در مهندسی دریا بحساب میآید. مشاهدات عینی نشان داد، خطوط لوله که بر بستر فرسایشی دریا و رودخانهها قرار گرفته، در اثر آبشستگی موضعی ایجاد شده، دچار دفن طبیعی(خوددفنی لوله) در بستر رسوبی میشود. اما در شرایط طبیعی فرآیند دفن با سرعت کمی اتفاق میافتد. از اینرو با نصب زائدهای روی خطوط لوله، سعی در افزایش سطح مقطع عمود بر جریان(ایجاد تغییرات الگوی جریان در اطراف خط لوله) و نهایتاً وقوع فرسایش در سرعتهای محیطی کمتر و با شدت بیشتر میباشد. مطالعات پیشین نشان میدهد که نصب باله در بالای خط لوله، سبب افزایش مقدار فرسایش در اطراف لوله میشود. کاربرد پیگیبکلاین(Piggyback line) نصب شده با شکل مقطع و زوایای متفاوت، روی خطوط لوله اصلی میتواند تفاوت عمدهای با تحقیقات انجام شده قبلی داشته باشد. در پژوهش حاضر، به روش پای-باکینگهام(Pi-Bukingham) تمامی متغیرهای تأثیرگذار بر ابعاد آبشستگی موضعی زیر خطوط لوله، تحلیل ابعادی شده است. و تأثیر پارامترهای بدون بعد بدست آمده مورد بررسی و تحلیل قرار گرفته است. نتایج آزمایشگاهی حاکی از آن است که، آبشستگی لوله به همراه پبگببکلاین تا 2 برابر نسبت به لوله ساده افزایش یافته است. پیگیبکلاین با شکل مقطع مثلثی، برای افزایش مقدار عمق حداکثر آبشستگی در زاویه نصب منفی 135 درجه، دارای بهترین عملکرد بوده است. و در بستر ریزدانه بطور میانگین تا 4 برابر و در بستر درشتدانه بطور میانگین تا 6 برابر عمق آبشستگی را نسبت به حالت لوله ساده افزایش میدهد.
کلیدواژه‌ها
موضوعات
عنوان مقاله [English]
Evaluation of the Time Development of Scour Around Pipelines With Optimization the Mounting Position of Piggyback-Line
نویسندگان [English]
- Sobhan Moradi 1
- Kazem Esmaili 2
- Saeid Reza Khodashenas 3
1 Ph.D. Student, Ferdowsi University of Mashhad, Agriculture Collage, Water Structure Engineering Faculty.
2 Associate Professor,Ferdowsi University of Mashhad, Agriculture Collage, Water Engineering Faculty.
3 Professor, Ferdowsi University of Mashhad, Agriculture Collage, Water Engineering Faculty.
چکیده [English]
Protection of water pipelines - wastewater or fuel materials - on the bed of erosion of the sea and rivers against such factors as bending, slipping and even fracture are important and costly issues in ocean engineering. In order to protect the potential destruction and fracture of these pipelines due to hydrodynamic forces of flow-waves or human activities. It is necessary to be covered with a concrete-coat or buried at an appropriate depth of bed with trenching.Objective observations showed that the pipelines that are located on the erosion bed of the sea and the rivers have the potential to produce a natural burial (self-burial pipe) in a bed of sediment, due to localized scouring.But in natural conditions, the burial process takes place with little speed. Therefore, by installing the spoiler on the pipelines, it is attempting to increase the Perpendicular cross-section of the flow (making changes in the pattern of flow around the pipeline) and, finally, the occurrence of erosion and self-burial inlower environmental velocities, but more intense. Therefore, it is necessary to first investigate the factors affecting for erosion sediment bed and estimate the dimensions of scour hole under pipelines, to study the accelerating factors and its effects on ocean engineering.
Themost of researchers considered the local scouring around the pipelines relatede to be rapid, the depth of the flow, the pipe diameter and the particle size of the bed. Moncada-M and Aguirre-Pe (1999) describe that, the scour depth below the pipeline as a function of the flow loss number and the dimensionless distance between the pipe and the intact bed. Cheng and Chew (2003) and Zhao and Wang (2009), by simulating the flow area around the pipeline with the mounted fin on it, found that the lifting force and shear stress in the bed and the scour depth increased with the fin. (2012), by using laboratory results, showed that the flow loss number and the height of the fin had a significant effect on the depth of scouring under the horizontal pipelines. Shan et al. (2015) with numerical evaluation of self-burial of tube with the fin mounted on it, and in displacement mode, with Fluent software, found that increasing the flow loss number in near of the bed would help to increase the burial speed of the tube.
recently studies showed that the mounting of the fins on the pipeline lead to increasing the amount of erosion around the tube. The application of mounted Piggyback line with cross sectional and different angles on the main pipelines can be a major difference with previous research.
کلیدواژه‌ها [English]
- Tunnel erosion
- Scour
- Piggyback-line
- pipeline
1- Ataeiyan, A. and Yasi, M., 2012. Estimate the maximum depth of scour around a pipeline crossing the river. 11th Conference of Hydraulic of iran. (In Persian).
2- Bijker, E.W. and Leeuwestein, W., 1984. Interaction between pipelines and the seabed under the influence of waves and currents. In Seabed Mechanics (pp. 235-242). Springer, Dordrecht.
3- Cheng, L. and Chew, L.W., 2003. Modelling of flow around a near-bed pipeline with a spoiler. Ocean Engineering, 30(13), pp.1595-1611.
4- Chiew, Y.M., 1990. Mechanics of local scour around submarine pipelines. Journal of Hydraulic Engineering, 116(4), pp.515-529.
5- Chiew, Y.M., 1992. Effect of spoilers on scour at submarine pipelines. Journal of Hydraulic Engineering, 118(9), pp.1311-1317.
6- Dey, S. and Singh, N.P., 2008. Clear-water scour below underwater pipelines under steady flow. Journal of Hydraulic Engineering, 134(5), pp.588-600.
7- Hansen, E.A., Staub, C., Fredsøe, J. and Sumer, B.M., 1991. Time-development of scour induced free spans of pipelines. In Proceedings, 10th Conference on Offshore Mechanics and Arctic Engineering, Pipeline Technology. Vol. 5, pp. 25-31.
8- Hulsbergen, C.H., 1986, January. Spoilers for stimulated self-burial of submarine pipelines. In Offshore technology Conference. Offshore Technology Conference.
9- Hulsbergen, C.H. and Bijker, R., 1989, January. Effect of spoilers on submarine pipeline stability. In Offshore Technology Conference. Offshore Technology Conference.
10- Ibrahim, A. and Nalluri, C., 1986. Scour prediction around marine pipelines. In Proc., 5th International Symp. on Offshore Mechanics and Arctic Engineering, American Society of Mechanical Engineers, pp. 679-684.
11- Kjeldsen, S.P., Gjorsvik, O., Bringaker, K.G. and Jacobsen, J., 1973, August. Local scour near offshore pipelines. In Paper available only as part of the complete Proceedings of the Second International Conference on Port and Ocean Engineering Under Arctic Conditions (POAC), August 27-30, 1973..
12- Ye, M., 1986. The interaction between a pipeline and an erodible bed. Institute of Hydrodynamics and Hydraulic Engineering, Technical University of Denmark.
13- Alvarez, M. and Antonio, J., 1989. Introduction to river engineering. In Introduction to River Engineering. Universitá Italiana per Stranieri.
14- Melville, B.W., 1997. Pier and abutment scour: integrated approach. Journal of Hydraulic Engineering, 123(2), pp.125-136.
15- Moncada-M, A.T. and Aguirre-Pe, J., 1999. Scour below pipeline in river crossings. Journal of Hydraulic Engineering, 125(9), pp.953-958.
16- Dandan, S.H.A.N., Yanyan, L.I.U. and Yang, L.I., 2015. Numerical Simulation of Submarine Pipeline Self-Buried on Sediment Seabed. Advances in Petroleum Exploration and Development, 10(1), pp.44-50.
17- Sumer, B.M. and Fredsøe, J., 1990. Scour below pipelines in waves. Journal of waterway, port, coastal, and ocean engineering, 116(3), pp.307-323.
18- Sumer, B.M. and Fredsøe, J., 1993. A review of wave/current-induced scour around pipelines. In Coastal Engineering 1992. pp. 2839-2852.
19- Sumer, B.M. and Fredsøe, J., 2002. The mechanics of scour in the marine environment, Adv. Ser. Ocean Eng, 17.
20- Sumer, B.M., 2004, November. Physical and mathematical modelling of scour. In Proc., 2nd Int. Conference on Scour and Erosion, Vol. 1, pp. 29-46.
21- Yang, L., Guo, Y., Shi, B., Kuang, C., Xu, W. and Cao, S., 2012. Study of scour around submarine pipeline with a rubber plate or rigid spoiler in wave conditions. Journal of waterway, port, coastal, and Ocean Engineering, 138(6), pp.484-490.
22- Yang, C.T., 1996. Sediment transport: Theory and Practice.
23- Zhao, J. and Wang, X., 2008. CFD Numerical Simulation of the Submarine Pipeline With Spoiler. In ASME 2008 Pressure Vessels and Piping Conference (pp. 21-27). American Society of Mechanical Engineers.
24- Zhao, X.Z., Sun, Z.C. and Liang, S.X., 2009. A numerical study of the transformation of water waves generated in a wave flume. Fluid Dynamics Research, 41(3), p.035510.
