بررسی آزمایشگاهی اثر تخلخل و زاویه موانع نفوذپذیر بر رسوب‌گذاری جریان غلیظ

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشگاه فردوسی مشهد

2 علوم ومهندسی آب/ دانشکده کشاورزی/ دانشگاه فردوسی مشهد

3 دانشکده مهندسی، گروه عمران، دانشگاه فردوسی مشهد

چکیده

جریان سیالبی رودخانه‌ها اغلب از نوع جریان غلیظ است. از این رو، شناخت و بررسی این جریان‌ها می‌تواند بخشی از مسائل رسوب‌گذاری را بر طرف نماید. در این پژوهش، اثر تخلخل و زاویه موانع نفوذپذیر بر کنترل و تله‌اندازی جریان غلیظ در آزمایشگاه بررسی شده است. برای این منظور، از یک پلیمر نامحلول و معلق ساخته شده از پلی استایرن انبساطی (EPS )با چگالی 1/135 گرم در لیتر و متوسط قطر 1/15 میلی‌متر استفاده شد. موانع از صفحات پلاکسی گلاس انتخاب شدند که از دو نوع شیاری و حفرهای با عرض شیارها و قطر حفره‌هایی برابر با 3 میلیمتر ساخته شدند. آزمایش‌ها با دو غلظت متفاوت (10 و 20 درصد)، پنج تخلخل و چهار زاویه‌ی مختلف انجام شد. نتایج نشان دادند که با افزایش تخلخل، میزان تله‌اندازی تا تخلخل بهینه روند کاهشی و سپس افزایشی دارد. بر این اساس، تخلخل بهینه برای موانع حفرهای و موانع شیاری به ترتیب 22 و 19 درصد به دست آمد. در همه‌ی آزمایش‌ها، تله‌اندازی حفرهای، با 0/13 و 0/14 درصد به ترتیب در غلظت‌های ۱۰ و ۲۰ درصد، بیشتر از شیاری بود. علاوه بر این، با افزایش زاویه، مقدار تله‌اندازی کاهش یافت و مقدار آن در شیاری نسبت به حفرهای به ترتیب با ضریب همبستگی‌هایی برابر 0/961 و 0/937 ،بیشتر مشاهده شد. اثر عمده موانع، کاهش سرعت و ایجاد کندی جریان تشخیص داده شد که متوسط سرعت در حفرهای 3/62 درصد بیشتر از شیاری به دست آمد. بر مبنای نتیجه‌ها، در شرایط مشابه، همواره موانع حفرهای عملکرد بهتری از موانع شیاری دارند.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Experimental Investigation Effect of the Porosity and Angle of Permeable Obstacles on Density Current Sedimentation

نویسندگان [English]

  • Alireza Jahangir 1
  • kazem Esmaili 2
  • Mahmoud Faghfour Maghrebi 3
1 Ferdowsi University of Mashhad
2 Head of dept.
3 Civil Engineering Department, Engineering Faculty, Ferdowsi University of Mashhad
چکیده [English]

Flood flow in rivers is often of density current type. Hence, recognizing and exploring these currents can solve some problems of sedimentation. In this study, the effect of porosity and the angle of permeable obstacles on the control and trapping of density current have been investigated in the laboratory. For this purpose, an expanded polystyrene (EPS) polymer was used with 1.135 g/L density and average diameter of 1.15 mm. The experiments were carried out with two concentrations (10 and 20%) and 5 porosity and 4 angles. The obstacles were made of palsy glass plates and two types of groove and cavity with 8.2 mm width of the groove and the diameter of the cavity. The results showed that, with an increase in porosity ratio, the amount of trapping to optimum porosity decreases and then increases. The optimal porosity of the cavity and groove is 22 % and 19%, respectively. In experiments, the cavity trapping was observed more than the groove, in the concentrations of 10.20% it was 0.13 and 0.14%, respectively. Also, with the increase of the angle, the amount of trapping has reduced and its value was observed in the groove more than the cavity. The correlation coefficient in the grooves and cavities was 0.996 and 0.937, respectively. The major effect of obstacles, reducing velocity and slowing flow were identified as the average velocity in the cavity was 3.62% higher than the groove. Accordingly, in the same conditions, the cavity obstacles have better performance than the groove obstacles.

کلیدواژه‌ها [English]

  • Density current
  • Suspended Sedimentation
  • Permeable Obstacle
  • Obstacle Angle
  • Obstacle porosity
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