اثر ضخامت و تعداد مانع‌های نفوذپذیر بر کنترل و تله‌اندازی جریان غلیظ

محورهای موضوعی : مدیریت آب در مزرعه با هدف بهبود شاخص های مدیریتی آبیاری

علیرضا جهانگیر ¹ (داشنشجوی دکتری، گروه مهندسی آب دانشگاه فردوسی مشهد، مشهد، ایران)
کاظم اسماعیلی ² (دانشیار گروه مهندسی آب دانشگاه فردوسی مشهد، مشهد، ایران)
محمود فغفور مغربی ³ (استاد گروه مهندسی عمران دانشگاه فردوسی مشهد، مشهد، ایران)

تاریخ دریافت : 1399/03/13 تاریخ پذیرش : 1399/05/05 تاریخ انتشار : 1400/03/01

کلید واژه: مانع نفوذپذیر, جریان غلیظ, ضخامت مانع, لایه‌ی دوم مانع, رسوب‌گذاری معلق,

چکیده مقاله :

شناخت و بررسی جریان سیلابی رودخانه‌ها که در بیشتر موردها از نوع جریان غلیظ است، می‌تواند به کاهش اثرهای نامطلوب رسوب‌گذاری کمک کند. برای این منظور، ایجاد مانع‌ها در بستر جریان‌ موثر خواهد بود. در این مقاله به‌صورت آزمایشگاهی، اثر ضخامت (بعد) و لایه‌ی دوم موانع نفوذپذیر بر کنترل و تله‌اندازی جریان غلیظ مورد ارزیابی قرار گرفته است. برای این منظور، از دو گونه مانع‌های شیاری و حفره‌ای دارای شیارها و قطر حفره‌هایی برابر با 3 میلیمتر و ساخته‌شده از صفحات پلاکسی گلاس بهره‌جویی شده است. جریان غلیظ با اضافه کردن یک پلیمر نامحلول و معلق از جنس پلی استایرن انبساطی با میانگین قطر 15/1 میلیمتر و چگالی 135/1 گرم در لیتر ایجاد شد. در انجام آزمایش‌ها از دو غلظت متفاوت (10 و 20 درصد)، پنج تخلخل گوناگون، چهار زاویه‌ی مختلف، چهار ضخامت متفاوت و با دو لایه مانع بهره‌جویی شد. نتیجه‌ها نشان دادند روند عبور جریان غلیظ دارای تخلخل 10 درصد از مانع‌ شیاری با افزایش ضخامت بیشتر می‌شود. لایه‌ی دوم مانع‌ها باعث افزایش روند عبور مواد از هر دو مانع‌های شیاری و حفره‌ای شده است. میزان این افزایش در نوع شیاری برابر 96/1 و نوع حفره‌ای برابر 34/2 ثبت شد. بررسی‌ها نشان دادند که فاصله‌ی بهینه مانع دوم از اول معادل 25/2 متر می‌باشد. بر مبنای نتیجه‌ها، در شرایط مشابه، همواره موانع حفره‌ای عملکرد بهتری از موانع شیاری دارند.

چکیده انگلیسی:

Understanding and studying the river flooding, which in most cases is density current, can help to reduce adverse effects of sedimentation. To this end, the creation of obstacles in the bed of stream will be effective. In this paper, the effect of thickness (dimension) and the second layer of permeable obstacles on the control and trapping of density current is investigated experimentally. For this purpose, two types of groove and cavity obstacles with grooves and cavity diameters equal to 3 mm and made of plaque glass were used. Density currents were created by adding an insoluble, suspended polymer of expanded polystyrene with a mean diameter of 1.15 mm and a density of 1.155 g / l. The experiments utilized two different concentrations (10 and 20%), five different porosities, four different angles, four different thicknesses and two barrier layers. The results showed that the density current process with 10% porosity of the groove obstacle increased with increasing thickness. The second layer of obstacles have increased the material passage through both groove and cavity obstacles. This increase was recorded in the groove type of 1.96 and the cavity type of 2.34. Investigations showed that the optimal distance of the second obstacle from the first was 2.25 meters. According to the results, under similar conditions, cavity obstacles always perform better than groove ones.

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