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Derivation of settling velocity, eddy diffusivity and pick-up rate from field-measured suspended sediment concentration profiles in the horizontally uniform but vertically unsteady scenario
Applied Ocean Research ( IF 4.3 ) Pub Date : 2020-12-23 , DOI: 10.1016/j.apor.2020.102485
Shaotong Zhang , Peter Nielsen , Pierre Perrochet , Beibei Xu , Yonggang Jia , Mingzheng Wen

Accurate determinations of sediment settling velocity (ws), eddy diffusivity (Ds), and pick-up rate p(t) from available field data are vital for engineering calculations or numerical simulations of coastal processes. Existing methods to determine these parameters are normally based on the assumption of a steady equilibrium that ignores the “phase lag” and “amplitude damping” effects of a diffusing concentration in unsteady scenarios that are typical of many field settings. The present paper gives an analytical solution for a time-varying suspended sediment concentration profile C(z,t) in the horizontally uniform but one-dimensional vertical (1DV) unsteady scenario with a vertically constant Ds distribution. The model is used to estimate ws, Ds, and p(t) by determining best fits between the modelled and C(z,t) profiles measured with an instrumented quadripod in the subaqueous Yellow River Delta (YRD) during a local sediment resuspension event. Values of field-derived ws range from 0.01 to 0.073 mm/s, while Ds range from 2 × 10−5 to 1.46 × 10−4 m2/s, and p(t) range from 8.3 × 10−5 to 3.14 × 10−4 kg m−2 s−1 under mild and energetic wave conditions, respectively, which are consistent with our laboratory measurements and with the results reported in the literature; time variations of the derived parameters are also reasonable in response to the synchronous hydrodynamics, both confirm that the parameter optimizations are successful. The proposed analytical model is shown to be a practical tool for inferring ws, Ds, and p(t) from available measured C(z,t) profiles free of secondary prediction equations or unknown empirical parameters.



中文翻译:

在水平均匀但垂直不稳定的情况下,通过现场测量的悬浮沉积物浓度剖面推导沉降速度,涡流扩散率和吸收率

从可用的现场数据中准确确定沉积物的沉降速度(w s),涡流扩散率(D s)和吸收速率pt)对于沿海工程的工程计算或数值模拟至关重要。确定这些参数的现有方法通常基于稳定平衡的假设,该假设忽略了在许多现场设置中常见的不稳定情况下扩散浓度的“相位滞后”和“振幅阻尼”效应。本文给出了时变悬浮泥沙浓度曲线Cz,t)在水平方向一致但D s分布恒定的一维垂直(1DV)非稳态场景中。该模型用于通过确定模型和Cz,t)剖面之间的最佳拟合来估算w sD spt),这些剖面通过仪器四足动物在黄河三角洲(YRD)局部沉积期间测得重悬事件。场源w s的值范围为0.01到0.073 mm / s,而D s的范围为2×10 -5到1.46×10 -4 m 2/ s和pt)分别在轻度和高能波条件下的范围从8.3×10 -5到3.14×10 -4 kg m -2 s -1,这与我们的实验室测量结果和文献; 响应于同步流体动力学,导出参数的时间变化也是合理的,都证实了参数优化是成功的。所提出的分析模型被示出为一个实用的工具用于推断瓦特小号d小号,和p从可用的测量)ÇZ,T)不含二次预测方程式或未知经验参数的配置文件。

更新日期:2020-12-23
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