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	Influence of bed clusters and size gradation on operational time distribution for non-uniform bed-load transport
	Zhang Y.; Chen, D.; Garrard, R.; Sun, H. G.; Lu, Y. H.
	2016
关键词	operational time distribution bed-load transport clusters static bed armouring mobile bed armouring random-walk method gravel-bed sediment-transport bedload transport advection-dispersion selective transport fractional dynamics turbulent flows rivers model
英文摘要	The operational time distribution (OTD) defines the time for bed-load sediment spent in motion, which is needed to characterize the random nature of sediment transport. This study explores the influence of bed clusters and size gradation on OTD for non-uniform bed-loads. First, both static and mobile bed armouring experiments were conducted in laboratorial flumes to monitor the transport of mixed sand/gravel sediments. Only in the mobile armouring experiment did apparent bed clusters develop, because of stable feeding and a longer transport period. Second, a generalized subordinated advection (GSA) model was applied to quantify the observed dynamics of tracer particles. Results show that for the static armour layer (without sediment feed), the best-fit OTD assigns more weight to the large displacement of small particles, likely because of the size-selective entrainment process. The capacity coefficient in the GSA model, which affects the width of the OTD, is space dependent only for small particles whose dynamics can be significantly affected by larger particles and whose distribution is more likely to be space dependent in a mixed sand and gravel system. However, the OTD for the mobile armour layer (with sediment recirculation) exhibited longer tails for larger particles. This is because the trailing edge of larger particles is more resistant to erosion, and their leading front may not be easily trapped by self-organized bed clusters. The strong interaction between particle-bed may cause the capacity coefficient to be space-dependent for bed-load transport along mobile armour layers. Therefore, the combined laboratory experiments and stochastic model analysis show that the OTD may be affected more by particle-bed interactions (such as clusters) than by particle-particle interactions (e.g. hiding and exposing), and that the GSA model can quantify mixed-size sand/gravel transport along river beds within either static or mobile armour layers. Copyright (c) 2016 John Wiley & Sons, Ltd.
出处	Hydrological Processes
卷	30
期	17
页	3030-3045
收录类别	SCI
语种	英语
ISSN号	0885-6087
内容类型	SCI/SSCI论文
源URL	[http://ir.igsnrr.ac.cn/handle/311030/43918]
专题	生态系统网络观测与模拟院重点实验室_生态网络实验室
推荐引用方式 GB/T 7714	Zhang Y.,Chen, D.,Garrard, R.,et al. Influence of bed clusters and size gradation on operational time distribution for non-uniform bed-load transport. 2016.

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