کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
6380720 1625617 2016 14 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
An experimental analysis of bed load transport in gravel-bed braided rivers with high grain Reynolds numbers
ترجمه فارسی عنوان
یک تحلیلی تجربی از انتقال بار بستر در رودخانه های بافته شده با سنگ آهک با اعداد رینولدز بالا
کلمات کلیدی
مورفولوژی رودخانه، رودخانه های بافته سیب، حمل بار تخت، قدرت جریان آزمایشات آزمایشگاهی، معیار مشخصات بستر
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات فرآیندهای سطح زمین
چکیده انگلیسی
Laboratory experiments were performed with nearly uniform fluvial gravel (D50=9 mm, D10=5 mm and D90=13 mm) to analyse the relationship between stream power and bed load transport rate in gravel-bed braided rivers at high grain Reynolds numbers. The values of the unit-width dimensionless bed-load rate qb* and unit-width dimensionless stream power ω* were evaluated in equilibrium conditions based on ten different experimental runs. Then, they were plotted along with values obtained during particularly representative field studies documented in the literature, and a regression law was derived. For comparison, a regression analysis was performed using the data obtained from laboratory experiments characterized by smaller grain sizes and, therefore, referring to relatively low grain Reynolds numbers. A numerical integration of Exner's equation was performed to reconstruct the local and time-dependent functional dependence of qb* and ω*. The results led to the following conclusions: 1) At equilibrium, the reach-averaged bed load transport rate is related to the reach-averaged stream power by different regression laws at high and low grain Reynolds numbers. Additionally, the transition from bed to suspended load transport is accelerated by low Re*, with the corresponding bed load discharge increasing with stream power at a lower, linear rate. 2) When tested against the gravel laboratory measurements, the high Re* power law derived in the present study performs considerably better than do previous formulas. 3) The longitudinal variability of the section-averaged equilibrium stream power is much more pronounced than that characterizing the bed load rate, at least for high Re*. Thus, the stream power and its local-scale heterogeneity seem to be directly responsible for transverse sediment re-distribution and, ultimately, for the determination of the spatial and temporal scales that characterize the gravel bedforms. 4) Finally, the stochastic interpretation of the wetted bed elevation function mapped in a particularly representative sample run reveals that gravel-bed transport and braiding are associated with the persistence of multiple equilibrium energy states due to the presence of truly non-stationary, local-scale pseudo-periodicity.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Advances in Water Resources - Volume 94, August 2016, Pages 160-173
نویسندگان
, , ,