Pore-resolved investigation of turbulent open channel flow over a randomly packed permeable sediment bed
Pore-resolved investigation of turbulent open channel flow over a randomly packed permeable sediment bed
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DOI：
10.1017/jfm.2023.636
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发表时间：
2023-08
影响因子：
3.7
通讯作者：
S. Karra;S. Apte;Xiaoliang He;Timothy Scheibe
中科院分区：
文献类型：
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作者：
S. Karra;S. Apte;Xiaoliang He;Timothy Scheibe
摘要本文采用孔分辨直接数值模拟方法，研究了渗透雷诺数Re_K=2.56、5.17和8.94时，水流紊动与地下水流在随机堆积多孔沉积物床中的相互作用。时空平均被用来量化的雷诺应力，形式诱导的应力，平均流量和剪切穿透深度，和混合长度在沉积物-水界面（SWI）。平均流量和剪切渗透深度随Re_K的增加而增加，并且是无因次渗透率的非线性函数。雷诺应力，形式引起的应力，和压力变化的峰值和显着的值显示发生在床的顶层，这也证实了进行模拟的只是顶层的粗糙度元素在一个不可渗透的墙壁。归一化的局部床面应力的概率分布函数（p.d.f.s）被发现崩溃的所有雷诺数，其均方根波动被假定为遵循对数相关。局部底床应力的波动和由此产生的阻力和升力对沉积物颗粒主要是一个结果的顶层;他们的p.d.f.s是对称的重尾，可以很好地代表了一个非高斯模型拟合。在SWI的床应力统计和压力数据可能可以用于提供更好的边界条件，在模拟的起动和到达尺度运输的潜流区。
Abstract Pore-resolved direct numerical simulations are performed to investigate the interactions between streamflow turbulence and groundwater flow through a randomly packed porous sediment bed for three permeability Reynolds numbers, $Re_K=2.56$, 5.17 and 8.94, representative of natural stream or river systems. Time–space averaging is used to quantify the Reynolds stress, form-induced stress, mean flow and shear penetration depths, and mixing length at the sediment–water interface (SWI). The mean flow and shear penetration depths increase with $Re_K$ and are found to be nonlinear functions of non-dimensional permeability. The peaks and significant values of the Reynolds stresses, form-induced stresses, and pressure variations are shown to occur in the top layer of the bed, which is also confirmed by conducting simulations of just the top layer as roughness elements over an impermeable wall. The probability distribution functions (p.d.f.s) of normalized local bed stress are found to collapse for all Reynolds numbers, and their root-mean-square fluctuations are assumed to follow logarithmic correlations. The fluctuations in local bed stress and resultant drag and lift forces on sediment grains are mainly a result of the top layer; their p.d.f.s are symmetric with heavy tails, and can be well represented by a non-Gaussian model fit. The bed stress statistics and the pressure data at the SWI potentially can be used in providing better boundary conditions in modelling of incipient motion and reach-scale transport in the hyporheic zone.