کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4687188 1635574 2007 10 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Simulation on sand grain/bed collision mechanism: Cascade collision and ejection (1)
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات فرآیندهای سطح زمین
پیش نمایش صفحه اول مقاله
Simulation on sand grain/bed collision mechanism: Cascade collision and ejection (1)
چکیده انگلیسی

Ejection of sand grains from a sand surface is assumed to result from cascade collision caused by the impact of a saltating particle. Allowing for only two-body cascade collision and introducing new quantities such as the cross-section for sand grain–grain collisions and sand surface binding energy, the theoretical model for the cascade collision of ion particles is applied to simulate sand grain/bed collision processes. The results of simulations indicate that the collision cascade events caused by impacting particles can eventually lead to the ejection of grains taking place from the sand surface. The number of ejected grains at any surface point is found to be proportional to the fractional energy deposited at that point and inversely proportional to the sand surface binding energy. This cascade collision model also confirms that the peak in the spatial distribution of ejected grains does not appear at the impact point but is located downwind, and that the speed distribution of ejected grains at a fixed angle exhibits a peak having a value directly related to the ratio of surface binding energy to the mass of the ejected grain. The angular distribution at a certain ejection speed also exhibits a maximum at an ejection angle near 90°. The model also offers a new interpretation for the observed variability in the number of ejected grains under constant impact velocity; this variability is directly related to the wide distribution of the energy deposition in the surface layer of the sand bed.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Geomorphology - Volume 89, Issues 3–4, 15 September 2007, Pages 348–357
نویسندگان
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