Sediment resuspension of bottom boundary layer under waves and currents
-
摘要: 海底沉积物再悬浮及其分布取决于海洋水动力、沉积物类型与床面形态之间复杂的相互作用，准确地理解和确定沉积物再悬浮过程对于沉积物输运的研究具有重要的意义。本文在祥云湾海洋牧场典型海域开展现场原位观测，获取研究区波浪、海流及悬浮沉积物浓度数据；分析了波、流作用下海底边界层悬浮沉积物垂向分布特征，并探究了海洋水动力和床面形态对悬浮沉积物垂向分布的影响。结果表明，研究区波流之间的相互作用不显著，沉积物再悬浮受控于风暴浪作用，风暴浪作用下底床切应力可以达到沉积物临界切应力的10～15倍，沉积物的再悬浮滞后于风暴浪作用2～3 h。在波浪荷载微小的情况下，悬浮沉积物垂向分布呈现“I”型，波浪荷载下，悬浮沉积物垂向分布呈现幂指函数分布，表现为“L”型；床面形态随波、流作用而演化，影响沉积物的再悬浮过程，
${u_{*w}}{\rm{/}}{u_{*c}} = 1.00$ 可作为波浪和海流起主导控制作用的床面形态的判别依据，纯波浪荷载作用下的${u_{*w}}{\rm{/}}{u_{*c}}$ 显著高于波浪主控作用下，但二者之间的界线随着波浪荷载的增加而升高。Abstract: Resuspension and its distribution of sediment depend upon three interacting components namely the characteristics of the mobile sediment, the bed forms and the forcing hydrodynamics. A good understanding of the process of sediment resuspension is important in sediment transport. In this paper, in-situ measurements of wave, current, and suspended sediment concentration profiles in the marine ranching of Xiangyun Bay were carried out. The vertical distribution characteristics of suspended sediment in the bottom boundary layer under the wave-current action were analyzed. The results show that the resuspension of seabed sediments in the study area is controlled by storm-waves. The bottom shear stress under storm wave is 10−15 times of the critical shear stress of sediment, resuspension of sediment lags behind storm-wave for 2−3 hours. The type of vertical distribution of suspended sediment is "I" under small wave load, the vertical distribution of suspended sediment in the bottom boundary layer presents a power exponential function, which is "L" type under storm-wave. Bedforms evolved with wave and current action, and which affected the resuspension process of sediments.${u_{*w}}{\rm{/}}{u_{*c}} = 1.00$ can be used as a criterion to distinguish the bedfroms under the dominant control of wave or current. The value of${u_{*w}}{\rm{/}}{u_{*c}}$ under wave load is higher than that under the dominant control of wave, and the cutoff value between them increased with the increase of wave load.-
Key words:
- bottom boundary layer /
- suspended sediment /
- waves /
- bedform /
- Xiangyun Bay
-
图 1 原位观测位置及观测设备示意图
Fig. 1 Schematic diagram of field observation area and observation equipment
图 3 2017年9−10月现场长期原位观测结果
a图中阴影为风暴浪事件
Fig. 3 Results of long term in-situ observation during September to October, 2017
The shaded in a represent strom wave event
图 4 2017年9−10月海流单独作用下的底床切应力（τc）、波浪荷载导致的底床切应力（τw）及波流共同作用下最大底床切应力（τmax）
横虚线代表沉积物临界切应力τcr=0.148 N/m2
Fig. 4 Bottom skin friction shear-stresses of current alone (τc), waves alone(τw), and maximum wave-current (τmax) during September to October, 2017
The horizontal line is the threshold shear-stress for the initiation of movement for D50 of the bed
图 5 2017年9−10月海底边界层不同深度处悬浮沉积物变化
Fig. 5 Variation of suspended sediment of bottom boundary layer at different depth during September to October, 2017
图 6 风暴荷载下悬浮沉积物垂向分布与波高的关系
Fig. 6 Vertical distribution of suspended sediments and wave height during storm
图 8 2017年9−10月波、流摩阻流速比值
${u_{*w}}/{u_{*c}}$ 时间序列变化Fig. 8 The ratio of wave and current friction velocity
${u_{*w}}/{u_{*c}}$ plotted as a function of time during September to October, 2017表 1 海底边界层综合观测平台搭载仪器简介
Tab. 1 Introduction of instruments on integrated observing platform of bottom boundary layer
序号 仪器 厂家/型号 基本参数 参数设置 1 波潮仪 加拿大RBR公司/RBR virtuoso D|wave & Tidal 测量精度不小于0.05%，潮位、波浪采样频率1～6 Hz可调 采样频率6 Hz，采样周期15 min，距底高度165 cm 2 多普勒流速仪 美国Norterk公司/ADV 采样频率最大为250 Hz，最大输出频率为64 Hz，测量精度为0.1%±0.5 cm/s 采集频率8 Hz；采样周期10 min，距底高度113 cm 3 多参数浊度仪 加拿大RBR公司/XR-620 CTDTu 测量温度、电导、深度、浊度、溶解氧；浊度：0～125 FTU、0～250 FTU、0～500 FTU、0～4 000 FTU 1 min采集一次，连续采集，距底高度82 cm 4 高密度悬浮泥沙浊度剖面测量仪 德国Argus公司/ASM-4-N 悬浮沉积物浓度量程：沙0～50 000 mg/L；泥0～5 000 mg/L；剖面测量范围海底面以上1～2 m；沉积物浓度测量精度±10% 采样频率1 Hz，采样周期15 min，底端第一个探头距底高度17 cm 
下载: 导出CSV
-
[1] Van Rjin Consultant L C, Ribberink J S, Van Der Werf Engineer J, et al. Coastal sediment dynamics: recent advances and future research needs[J]. Journal of Hydraulic Research, 2013, 51(5): 475−493. doi: 10.1080/00221686.2013.849297 [2] Davies A G, Thorne P D. Advances in the study of moving sediments and evolving seabeds[J]. Surveys in Geophysics, 2008, 29(1): 1−36. doi: 10.1007/s10712-008-9039-x [3] Thorne P D, Williams J J, Davies A G. Suspended sediments under waves measured in a large-scale flume facility[J]. Journal of Geophysical Research: Oceans, 2002, 107(C8): 3178. doi: 10.1029/2001JC000988 [4] Taal L J. Field measurements of vertical suspended sand concentration profiles in the surfzone in Egmond aan Zee, the Netherlands[D]. Utrecht: Utrecht University, 2015. [5] Van Rijn L C. Principles of Sediment Transport in Rivers, Estuaries and Coastal Seas[M]. Amsterdam, The Netherlands: Aqua Publications, 1993. [6] O'Brien M P. Review of the theory of turbulent flow and its relation to sediment-transportation[J]. Eos, Transactions American Geophysical Union, 1933, 14(1): 487−491. doi: 10.1029/TR014i001p00487 [7] Rouse H. Modern conceptions of the mechanics of fluid turbulence[J]. Trans ASCE, 1937, 102(3): 463−543. [8] Middleton G V, Southard J B. Mechanics of Sediment Movement[M]. 2nd ed. Oklahoma: SEPM, 1984. [9] Zheng Jun, Li Ruijie, Feng Qing, et al. Vertical profiles of fluid velocity and suspended sediment concentration in nearshore[J]. International Journal of Sediment Research, 2013, 28(3): 406−412. doi: 10.1016/S1001-6279(13)60050-5 [10] O’Hara Murray R B, Hodgson D M, Thorne P D. Wave groups and sediment resuspension processes over evolving sandy bedforms[J]. Continental Shelf Research, 2012, 46: 16−30. doi: 10.1016/j.csr.2012.02.011 [11] Grant W D, Madsen O S. The continental-shelf bottom boundary layer[J]. Annual Review of Fluid Mechanics, 1986, 18(1): 265−305. doi: 10.1146/annurev.fl.18.010186.001405 [12] Camenen B. Estimation of the wave-related ripple characteristics and induced bed shear stress[J]. Estuarine, Coastal and Shelf Science, 2009, 84(4): 553−564. doi: 10.1016/j.ecss.2009.07.022 [13] Huisman C E. Sediment concentrations and diffusivity profiles under skewed waves from ripple to sheet flow regime[D]. Utrecht: Utrecht University, 2009. [14] Kleinhans M G. Phase diagrams of bed states in steady, unsteady, oscillatory and mixed flows[M]//Van Rijn L, Soulsby R L, Hoekstra S P, et al. Sandpit Project. Amsterdam: Aqua Publications, 2005. [15] Soulsby R L. Dynamics of Marine Sands. A Manual for Practical Applications[M]. London: Thomas Telford Publications, Thomas Telford Services Ltd, 1997. [16] 陈文超, 邱若峰, 邢容容, 等. 基于强浪下的祥云岛岸滩侵淤特征及防护措施[J]. 海洋地质前沿, 2016, 32(11): 40−46.Chen Wenchao, Qiu Ruofeng, Xing Rongrong, et al. Beach erosion and deposition under storm and defense measures[J]. Marine Geology Frontiers, 2016, 32(11): 40−46. [17] 孙林云, 孙波, 刘建军, 等. 京唐港粉沙质海岸风暴潮骤淤及整治工程措施物理模型试验[J]. 中国港湾建设, 2010(Z1): 28−31, 52. doi: 10.3969/j.issn.1003-3688.2010.z1.006Sun Zhiyun, Sun Bo, Liu Jianjun, et al. Physical model tests on sudden siltation caused by storm and mitigation measures for fine sand coast in Jingtang Port[J]. China Harbour Engineering, 2010(Z1): 28−31, 52. doi: 10.3969/j.issn.1003-3688.2010.z1.006 [18] 邢超锋, 何青, 郭磊城, 等. ASM在近底泥沙浓度剖面观测中的应用研究[J]. 泥沙研究, 2015(6): 46−51.Xing Chaofeng, He Qing, Guo Leicheng, et al. Application of ASM at the bottom observation of suspended sediment concentration[J]. Journal of Sediment Reasearch, 2015(6): 46−51. [19] Downing J. Twenty-five years with OBS sensors: The good, the bad, and the ugly[J]. Continental Shelf Research, 2006, 26(17/18): 2299−2318. [20] 薛元忠, 何青, 王元叶. OBS浊度计测量泥沙浓度的方法与实践研究[J]. 泥沙研究, 2004(4): 56−60. doi: 10.3321/j.issn:0468-155X.2004.04.010Xue Yuanzhong, He Qing, Wang Yuanye. The method and application of OBS in the measurement of sediment concentration[J]. Journal of Sediment Reasearch, 2004(4): 56−60. doi: 10.3321/j.issn:0468-155X.2004.04.010 [21] 鲁远征, 吴加学, 刘欢. 河口底边界层湍流观测后处理技术方法分析[J]. 海洋学报, 2012, 34(5): 39−49.Lu Yuanzheng, Wu Jiaxue, Liu Huan. An integrated post-processing technique for turbulent flows in estuarine bottom boundary layer[J]. Haiyang Xuebao, 2012, 34(5): 39−49. [22] Chanson H, Trevethan M, Aoki S I. Acoustic Doppler velocimetry (ADV) in small estuary: Field experience and signal post-processing[J]. Flow Measurement and Instrumentation, 2008, 19(5): 307−313. doi: 10.1016/j.flowmeasinst.2008.03.003 [23] Yang Yang, Wang Yaping, Gao Shu, et al. Sediment resuspension in tidally dominated coastal environments: new insights into the threshold for initial movement[J]. Ocean Dynamics, 2016, 66(3): 401−417. doi: 10.1007/s10236-016-0930-6 [24] Bolaños R, Thorne P D, Wolf J. Comparison of measurements and models of bed stress, bedforms and suspended sediments under combined currents and waves[J]. Coastal Engineering, 2012, 62: 19−30. doi: 10.1016/j.coastaleng.2011.12.005 [25] Arnott R W C, Southard J B. Exploratory flow-duct experiments on combined-flow bed configurations and some implications for interpreting storm-event stratification[J]. Journal of Sedimentary Petrology, 1990, 60(1): 211−219. [26] Kobayashi N, Zhao Haoyu, Tega Y. Suspended sand transport in surf zones[J]. Journal of Geophysical Research: Oceans, 2005, 110(C12): C12009. doi: 10.1029/2004JC002853 [27] Nielsen P. Coastal bottom boundary layers and sediment transport[M]//Liu P L F. Advanced Series on Ocean Engineering. Singapore: World Scientific Publishing Co. Pte. Ltd., 1992. [28] Li M Z, Amos C L. Predicting ripple geometry and bed roughness under combined waves and currents in a continental shelf environment[J]. Continental Shelf Research, 1998, 18(9): 941−970. doi: 10.1016/S0278-4343(98)00034-X -
计量
- 文章访问数: 878
- HTML全文浏览量: 152
- PDF下载量: 143
- 被引次数: 0
