کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
1720653 1520354 2015 10 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Direct bed shear measurements under loose bed swash flows
ترجمه فارسی عنوان
اندازه گیری های برش مستقیم تخت بستگی به جریان شستشوی تخت دارد
موضوعات مرتبط
مهندسی و علوم پایه سایر رشته های مهندسی مهندسی دریا (اقیانوس)
چکیده انگلیسی


• Shear stress measurements of loose bed swash flows are presented.
• Bed shear stress is measured directly with a shear plate.
• Fluid stress and grain stress contributions are identified.
• Data are in agreement with classical theory and later idealised measurements.
• Bed shear stress is up to twice that for equivalent fixed bed conditions.

Shear plate measurements of bed shear stress under fixed and loose bed swash uprush flows are presented and contrasted. A shear plate previously developed for fixed bed flows was modified and tested for coarse and fine grain loose beds. Transient flows were generated by a dam-break flow over initially dry horizontal and sloping beds, with flows upslope analogous to swash uprush flows on beaches. Performance of the shear plate varied with grain size. For the coarse grained loose beds only the peak shear stress at the leading edge of the swash flow was consistently obtained; for fine grained loose beds the shear stress was reliably obtained over the whole uprush swash cycle. Data were obtained for varying thickness of loose bed material, commencing with a single grain layer, which correspond to partially starved bed conditions. The direct measurements clearly indicate that the bed shear stress comprises of a fluid shear stress component and a grain shear stress component. The grain shear stress increases linearly with sediment load and is significantly larger for the coarse loose grain bed tests due to the much larger normal stress compared to that for fine grain loose bed tests with the same number of grain layers. The data show a high degree of consistency with the classical theory of Bagnold (1956) and the derived coefficient of dynamic internal friction is similar to that observed by Hanes and Inman (1985).

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Coastal Engineering - Volume 100, June 2015, Pages 67–76
نویسندگان
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