نوع مقاله : مقاله پژوهشی
نویسندگان
1 دانشجوی دکتری سازه های آبی، دانشکده کشاورزی، دانشگاه رازی
2 استادیار گروه علوم و مهندسی آب، دانشکده کشاورزی، دانشگاه رازی
3 دانشیار گروه علوم و مهندسی آب، دانشکده کشاورزی، دانشگاه رازی
چکیده
در پروژه‌های خطوط انتقال سیال، گذر لوله بصورت مدفون و نیمه‌مدفون از قوس‌های رودخانه‌ای گریزناپذیر است. این امر الگوی آبشستگی و رسوبگذاری مرسوم در قوس رودخانه را تغییر می‌دهد. الگوی آبشستگی اطراف خط لوله، نسبت به حالتی که خط لوله یک نهر مستقیم را قطع می‌کند، متفاوت است. نظر به گسترش خطوط انتقال در سال‌های اخیر، در این پژوهش تاثیر زاویه جانمایی خط لوله در قوس 90درجه ملایم و همچنین عمق جانمایی خط لوله بصورت آزمایشگاهی بررسی شد. آزمایش‌های این تحقیق در سه عدد فرود 0.32، 0.29 و 0.26، سه زاویه متفاوت 90، 67.5 و 45 درجه از قوس ملایم، دو حالت جانمایی لوله به‌صورت دافع و جاذب نسبت به جهت جریان و همچنین یک عمق نیمه‌مدفون و دو عمق مدفون به انجام رسید. نتایج نشان داد در حالت جانمایی به صورت دافع با افزایش زاویه نسبت به قوس، آبشستگی زیر و اطراف لوله افزایش می یابد. این روند برای آبشستگی اطراف لوله برای جانمایی لوله به صورت جاذب برعکس است اما برای آبشستگی زیر لوله همانند حالت قبل بود. همچنین با کاهش عدد فرود، میزان آبشستگی اطراف و زیر لوله کاهش می یابد؛ بطوریکه در برخی سناریوها، آبشستگی زیر لوله مشاهده نشد. این روند در افزایش عمق جانمایی لوله نیز مشاهده شد.
کلیدواژه‌ها
موضوعات
عنوان مقاله [English]
The effect of the angle and depth of the buried and semi-buried pipe on the amount of scouring and sedimentation around the pipe in a 90-degree mild bend using a laboratory model
نویسندگان [English]
- Rezvan Valizadeh 1
- Ali Arman 2
- RASOOL Ghobadian 3
1 Ph.D. student, Water Engineering branch, Campus of Agriculture and Natural Resources,, University of Razi
2 Assistant professor, Compus of Agriculture and Natural Resources, Razi University,
3 Associate professor, Compus of Agriculture and Natural Resources, Razi University,
چکیده [English]
Extended Abstract
Introduction
Due to the importance of the topic in the fluid transfer industry, the way of pipelines across the width and bed of the rivers has been considered especially in recent decades. In practice, the passage of pipelines through meandering rivers and river bends is unavoidable. In this research, local scouring of buried and semi-buried pipe in 90-degree mild bend under different scenarios was investigated. The results of this research can help the functioning of rivers and their interaction with structures in the river such as buried and semi-buried pipelines, predicting the amount of water washing around them and using its results in the design and placement of these pipelines.
Methodology
The laboratory model on which the scenarios of this research are based includes an arc-shaped channel located in the hydraulic laboratory and physical models of the water science and engineering department of Razi University. In this arc-shaped flume, the length of the upstream span is 5.4 meters, the length of the downstream span is 4.5 meters, the inner radius is 1.6 meters, the outer radius is 2.1 meters, the height is 0.6 meters, and the floor width is 0.5 meters. In order to check the correct functioning of the physical model and to trust its results, an experiment was conducted without the presence of the pipe buried in the bend. In this experiment, the flow descent number equal to 0.32 and sediments with a uniform grain and a diameter of 0.85 mm and a thickness of 15 cm were placed in the flume bed. After conducting the test for 6 hours and not observing the movement of the bed load, the pump was finally turned off and after the complete drainage of the flume, the bed profile was measured.
Results and Discussion
The effect of the placement angle of the repeller pipe relative to the mild arc (θ) on the scouring pattern
The results showed that by placing the pipe in the repulsive state, the amount of scour after the pipe and under the pipe has increased compared to the attracting state. According to the placement angles, it was observed that in repulsive mode, with the increase of the placement angle of the pipe in the bend, the amount of scouring after and under the pipe has increased. The effect of the placement angle of the attracting pipe relative to the mild arc (θ) on the scouring pattern In the absorbant state, it was observed that by approaching the beginning of the arc and reducing the placement angle of the pipe due to the non-alignment of the flow direction with the pipe direction, the amount of scour after the pipe decreased, but the process of scouring under the pipe was observed as in the repulsive state. The effect of pipe placement depth on scouring pattern
By increasing the depth of pipe placement, it was observed that the effect of the pipe on local erosion has decreased; Even in some simulation scenarios, the placement of the pipe in the depths with the ratio of the placement height to width of the channel of 0.06 buried pipe has no effect on the local erosion. It can be concluded that at depths equal to or greater than The ratio of placement depth to channel width is 0.06, the effect of local scouring caused by the buried and semi-buried pipe is minimal, and as a result, it causes the least damages.
Conclusions
The results showed that by placing the pipe in the repulsive state, the amount of scour after the pipe and under the pipe has increased compared to the attracting state. According to the placement angles, it was observed that in repulsive mode, with the increase of the placement angle of the pipe in the arch, the amount of scouring after and under the pipe has increased. However, in the absorbiant state, it was observed that by approaching the beginning of the arc and reducing the placement angle of the pipe due to the non-alignment of the flow direction with the direction of the pipe, the amount of scouring after the pipe decreased, but the process of scouring under the pipe was observed as in the repulsive state.
کلیدواژه‌ها [English]
- 90-degree mild bend
- pipe placement
- scouring
- buried and semi-buried pipe
- sedimentation
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