Effect of Porosity on Local Scour Around Circular Array of Cylinders in Steady Currents

doi:10.16183/j.cnki.jsjtu.2020.346

Abstract

Abstract:

The local scour around a circular array of cylindrical piles through physical model was studied under the live-bed condition, concerning the effect of porosity of the structure on the local scour development. The porosity of the model was achieved by varying the number of single piles, while the outer diameter of pile groups was kept as a constant. The effect of porosity on the equilibrium scour depth, the scour extent, and the time scale of scour was examined. It is found that the scour around the pile group is significantly affected by the porosity of the structure. As p>0.7, the resultant scour is mainly determined by the scour around each individual pile. As p<0.5, the scour is characterized by the pattern of one single pile with the same outer diameter as the pile group. As 0.5<p<0.7, the scour shows a pattern of transition from local scour to global scour. It is also found that the normalized equilibrium scour depth is a power function of p, with a power of approximately 0.67.

Key words: local scour, steady current, pile group, porosity

CLC Number:

TU473
TV 14

LIU Shihang, LOU Xiaofan, TANG Guoqiang, WANG Bin. Effect of Porosity on Local Scour Around Circular Array of Cylinders in Steady Currents[J]. Journal of Shanghai Jiao Tong University, 2022, 56(5): 664-674.

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References 24

[1]	ZDRAVKOVICH M M. The effects of interference between circular cylinders in cross flow[J]. Journal of Fluids and Structures, 1987, 1(2): 239-261. doi: 10.1016/S0889-9746(87)90355-0 URL
[2]	NEPF H M. Drag, turbulence, and diffusion in flow through emergent vegetation[J]. Water Resources Research, 1999, 35(2): 479-489. doi: 10.1029/1998WR900069 URL
[3]	STONE B M, SHEN H T. Hydraulic resistance of flow in channels with cylindrical roughness[J]. Journal of Hydraulic Engineering, 2002, 128(5): 500-506. doi: 10.1061/(ASCE)0733-9429(2002)128:5(500) URL
[4]	SHARPE R G, JAMES C S. Deposition of sediment from suspension in emergent vegetation[J]. Water SA, 2007, 32(2): 211-218.
[5]	TANINO Y, NEPF H M. Laboratory investigation of mean drag in a random array of rigid, emergent cylinders[J]. Journal of Hydraulic Engineering, 2008, 134(1): 34-41. doi: 10.1061/(ASCE)0733-9429(2008)134:1(34) URL
[6]	CASTRO I P. Wake characteristics of two-dimensional perforated plates normal to an air-stream[J]. Journal of Fluid Mechanics, 1971, 46(3): 599-609. doi: 10.1017/S0022112071000727 URL
[7]	CHEN D Y, JIRKA G H. Experimental study of plane turbulent wakes in a shallow water layer[J]. Fluid Dynamics Research, 1995, 16(1): 11-41. doi: 10.1016/0169-5983(95)00053-G URL
[8]	HUANG Z, KEFFER J F. Development of structure within the turbulent wake of a porous body. Part 1. The initial formation region[J]. Journal of Fluid Mechanics, 1996, 329: 103-115. doi: 10.1017/S0022112096008841 URL
[9]	ZONG L J, NEPF H. Vortex development behind a finite porous obstruction in a channel[J]. Journal of Fluid Mechanics, 2012, 691: 368-391. doi: 10.1017/jfm.2011.479 URL
[10]	NICOLLE A, EAMES I. Numerical study of flow through and around a circular array of cylinders[J]. Journal of Fluid Mechanics, 2011, 679: 1-31. doi: 10.1017/jfm.2011.77 URL
[11]	ATAIE-ASHTIANI B, BEHESHTI A A. Experimental investigation of clear-water local scour at pile groups[J]. Journal of Hydraulic Engineering, 2006, 132(10): 1100-1104. doi: 10.1061/(ASCE)0733-9429(2006)132:10(1100) URL
[12]	ZHAO H. The effect of flow skew angle on local sediment scour near pile groups[D]. Vita: University of Florida, 2004.
[13]	SALIM M, JONES J S. Scour around exposed pile foundations[C]// North American Water & Environment Congress & Destructive Water. Reston, Virginia: ASCE, 1999: 2002-2211.
[14]	AMINI A, MELVILLE B W, ALI T M, et al. Clear-water local scour around pile groups in shallow-water flow[J]. Journal of Hydraulic Engineering, 2012, 138(2): 177-185. doi: 10.1061/(ASCE)HY.1943-7900.0000488 URL
[15]	YAGCI O, YILDIRIM I, CELIK M F, et al. Clear water scour around a finite array of cylinders[J]. Applied Ocean Research, 2017, 68: 114-129. doi: 10.1016/j.apor.2017.08.014 URL
[16]	梁森栋, 张永良. 大桥复合桥墩局部冲刷深度的计算分析[J]. 水利学报, 2011, 42(11): 1334-1340.
	LIANG Sendong, ZHANG Yongliang. Analysis on the local scour around complex piers of a sea-crossing bridge[J]. Journal of Hydraulic Engineering, 2011, 42(11): 1334-1340.
[17]	曹帅, 张红武, 朱明东, 等. 多沙河流中群桩塔基局部冲刷平面尺度模型试验研究[J]. 水利学报, 2019, 50(6): 753-760.
	CAO Shuai, ZHANG Hongwu, ZHU Mingdong, et al. Experimental study on local scour plane size around the pile groups of tower foundation in sandy rivers[J]. Journal of Hydraulic Engineering, 2019, 50(6): 753-760.
[18]	RAUDKIVI A J, ETTEMA R. Clear-water scour at cylindrical piers[J]. Journal of Hydraulic Engineering, 1983, 109(3): 338-350. doi: 10.1061/(ASCE)0733-9429(1983)109:3(338) URL
[19]	MELVILLE B W, CHIEW Y M. Time scale for local scour at bridge piers[J]. Journal of Hydraulic Engineering, 1999, 125(1): 59-65. doi: 10.1061/(ASCE)0733-9429(1999)125:1(59) URL
[20]	SOULSBY R L, WHITEHOUSE R J S. Threshold of sediment motion in coastal environments [DB-OL]. (1997-01-01) [2020-10-08]. https://xueshu.baidu.com/usercenter/paper/show?paperid=22333e268fdc913d72d114b8c4071dd1.
[21]	WHITEHOUSE R. Scour at marine structures: A manual for practical applications[M]. Boston: International Ophthalmology Clinics, 1998.
[22]	FREDSØE J, SUMER B M, ARNSKOV M M. Time scale for wave/current scour below pipelines [DB-OL]. (1991-08-11) [2020-10-08]. https://trid.trb.org/view/440476.
[23]	MUTLU S B, BUNDGAARD K, FREDSØE J. Global and local scour at pile groups[J]. Proceedings of the International Offshore and Polar Engineering Conference, 2005, 15(3): 204-209.
[24]	CHEN Z B, ORTIZ A, ZONG L J, et al. The wake structure behind a porous obstruction and its implications for deposition near a finite patch of emergent vegetation[J]. Water Resources Research, 2012, 48(9): W09517.

编号	D/m	U/(m·s^-1)	h/m	n	p	S₀/m	h_s/m	L/m
1	0.2	0.37	0.5	4	0.878	0.0547	0.0650	0.3470
2	0.2	0.37	0.5	7	0.786	0.0854	0.0793	0.3480
3	0.2	0.37	0.5	10	0.694	0.1213	0.0842	0.6695
4	0.2	0.37	0.5	13	0.602	0.1559	0.0928	0.7640
5	0.2	0.37	0.5	16	0.510	0.1739	0.1054	0.8344
6	0.2	0.37	0.5	19	0.418	0.2133	0.0962	0.9535