Laboratory study of the effect of vegetation arrangement and density on flow resistance coefficient
محورهای موضوعی : Marine structures
سمیرا سلمان زاده
1
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منوچهر فتحی مقدم
2
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جواد احدیان
3
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سید محسن ساجدی
4
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کلید واژه: تراکم, Staggered arrangement, Resistance coefficient, flexible vegetation, drag force, ضریب مقاومت, آرایش زیگزاگی, پوشش گیاهی انعطافپذیر, نیروی درگ,
چکیده مقاله :
This paper has been done by considering the hydraulic conditions of the river flow and the morphological conditions of the vegetation along the river and floodplain. The hydrodynamic drag force was measured directly by use of loadcell in the presence of flexible vegetation. Accordingly, all experiments were performed in a flume named "knife edge flume" with 8.3 m length, 0.8 m width and a 0.55 m height. Flexible non-submerged vegetation models with 3 densities (30, 50 and 100%) and staggered arrangement in three relative water depths (0.6, 0.8 and 1) were tested. In this study, vegetation density changed with increasing distance and leaf area of models. The results showed that the drag force significantly depends on the density of vegetation as one of the measurable morphological features of the plant. Density results can be used as a useful criterion in estimating the resistance due to the presence of plant roughness in the river.
این مقاله با در نظر گرفتن شرایط هیدرولیکی جریان رودخانه و شرایط مورفولوژیکی پوشش گیاهی در حاشیه و سیلابدشت رودخانه انجام شده است. نیروی هیدرودینامیکی درگ در شرایط آزمایشگاهی و با استفاده از یک نیروسنج در حضور پوشش گیاهی انعطافپذیر به صورت مستقیم اندازهگیری شد. براین اساس تمامی آزمایشها در فلومی تحت عنوان " فلوم لبه چاقویی" با طول 3/8 متر، عرض 8/0 متر و ارتفاع 55/0 متر انجام شد. نمونه پوشش گیاهی انعطافپذیر به صورت غیرمستغرق با 3 تراکم 30، 50 و 100 درصد با آرایش زیگزاگی در سه عمق نسبی آب 6/0، 8/0 و 1 مورد آزمون واقع شد. در این مطالعه تراکم پوشش گیاهی با افزایش فاصله و سطح برگ گیاهان تغییر کرد. نتایج نشان داد نیروی درگ به میزان قابل توجهی به آرایش و تراکم پوشش گیاهی به عنوان یکی از ویژگیهای مورفولوژیکی قابل اندازهگیری گیاه بستگی دارد. نتایج مربوطه میتواند به عنوان معیار مفید در تخمین مقاومت ناشی از وجود زبریهای گیاهی در رودخانه باشد.
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