Influence of Collective Boulder Array on the Surrounding Time-averaged and Turbulent Flow Fields

CORC > 成都山地灾害与环境研究所 > 中国科学院水利部成都山地灾害与环境研究所 > Journal of Mountain Science > Journal of Mountain Science-2014 > Vol11 No.6

	Influence of Collective Boulder Array on the Surrounding Time-averaged and Turbulent Flow Fields
	Achilleas G. TSAKIRIS ; A.N. Thanos PAPANICOLAOU ; Seyed M. HAJIMIRZAIE ; James H.J. BUCHHOLZ
刊名	Journal of Mountain Science
	2014-11
卷号	11 期号:6 页码:1420-1428
关键词	Boulder array Form drag Bed shear stress Time-averaged velocity Turbulence intensity
通讯作者	A.N. Thanos PAPANICOLAOU
英文摘要	Arrays of large immobile boulders, which are often encountered in steep mountain streams, affect the timing and magnitude of sediment transport events through their interactions with the approach flow. Despite their importance in the quantification of the bedload rate, the collective influence of a boulder array on the approach time-averaged and turbulent flow field has to date been overlooked. The overarching objective is, thus, to assess the collective effects of a boulder array on the time-averaged and turbulent flow fields surrounding an individual boulder within the array, placing particular emphasis on highlighting the bed shear stress spatial variability. The objective of this study is pursued by resolving and comparing the time-averaged and turbulent flow fields developing around a boulder, with and without an array of isolated boulders being present. The results show that the effects of an individual boulder on the time-averaged streamwise velocity and turbulence intensity were limited to the boulder’s immediate vicinity in the streamwise (x/dc < 2-3) and vertical (z/dc < 1) directions. Outside of the boulder’s immediate vicinity, the time-averaged streamwise velocity was found to be globally decelerated. This global deceleration was attributed to the form drag generated collectively by the boulder array. More importantly, the boulder array reduced the applied shear stress exerted on the individual boulders found within the array, by absorbing a portion of the total applied shear. Furthermore, the array was found to have a “homogenizing” effect on the near-bed turbulence thus significantly reducing the turbulence intensity in the near-bed region. The findings of this study suggest that the collective boulder array bears a portion of the total applied bed shear stress as form drag, hence reducing the available bed shear stress for transporting incoming mobile sediment. Thus, the effects of the boulder array should not be ignored in sediment transport predictions. These effects are encapsulated in this study by Equation (6).
收录类别	SCI
公开日期	2014-11-18
内容类型	期刊论文
源URL	[http://ir.imde.ac.cn/handle/131551/7411]
专题	成都山地灾害与环境研究所_Journal of Mountain Science _Journal of Mountain Science-2014_Vol11 No.6
推荐引用方式 GB/T 7714	Achilleas G. TSAKIRIS,A.N. Thanos PAPANICOLAOU,Seyed M. HAJIMIRZAIE,et al. Influence of Collective Boulder Array on the Surrounding Time-averaged and Turbulent Flow Fields[J]. Journal of Mountain Science,2014,11(6):1420-1428.
APA	Achilleas G. TSAKIRIS,A.N. Thanos PAPANICOLAOU,Seyed M. HAJIMIRZAIE,&James H.J. BUCHHOLZ.(2014).Influence of Collective Boulder Array on the Surrounding Time-averaged and Turbulent Flow Fields.Journal of Mountain Science,11(6),1420-1428.
MLA	Achilleas G. TSAKIRIS,et al."Influence of Collective Boulder Array on the Surrounding Time-averaged and Turbulent Flow Fields".Journal of Mountain Science 11.6(2014):1420-1428.