TRANSPORT IN 3-DIMENSIONALLY HETEROGENEOUS AQUIFERS .1. DYNAMICS OF CONCENTRATION FLUCTUATIONS
TRANSPORT IN 3-DIMENSIONALLY HETEROGENEOUS AQUIFERS .1. DYNAMICS OF CONCENTRATION FLUCTUATIONS
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DOI：
10.1029/94wr00076
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发表时间：
1994-06-01
影响因子：
5.4
通讯作者：
GELHAR, LW
中科院分区：
文献类型：
--
作者：
KAPOOR, V;GELHAR, LW
由于浓度扰动的平方和速度扰动之间的相关性，浓度方差即浓度波动的均方根经历了平均平流、局部色散通量和宏观色散通量。宏观弥散系数与平均浓度场的梯度平方的乘积决定了浓度方差的产生速率。浓度方差的耗散率由局部色散系数与浓度扰动场均方梯度的乘积决定。方差耗散表示为一阶衰减，衰减系数等于局部色散系数之和除以微尺度浓度平方的两倍。对于以平流为主的测井水力导度微尺度，其浓度微尺度是测井导度微尺度的递增函数。因此，对数电导率微尺度越大，局部色散对浓度波动的耗散速度越慢，反之亦然。波动耗散的波数平方依赖性需要密集采样才能真实地模拟对数电导率谱及其微尺度，这决定了局部色散作用下浓度波动的耗散速率。没有局部分散的作用，就没有破坏浓度波动的机制。
The concentration variance, i.e., mean squared concentration fluctuations, undergoes mean advection, a local dispersive flux, and a macrodispersive flux due to a correlation between squared concentration perturbations and velocity perturbations. The products of the macrodispersion coefficient and the squared gradient of the mean concentration field determine the rate of production of concentration variance. The rate of dissipation of concentration variance is determined by the product of the local dispersion coefficient and the mean squared gradient of the concentration perturbation field. Variance dissipation is represented as a first-order decay with the decay coefficient equal to twice the sum of the local dispersion coefficient divided by the squared concentration microscale. The concentration microscale, estimated for an advection-dominated log hydraulic conductivity microscale, is an increasing function of the log conductivity microscale. Thus the larger the log conductivity microscale is, the slower is the rate of dissipation of concentration fluctuations by local dispersion and vice versa. The wave number squared dependence of fluctuation dissipation requires intensive sampling to realistically model the log conductivity spectrum and its microscale, which determines the rate of dissipation of concentration fluctuations by the action of local dispersion. There is no mechanism of destroying concentration fluctuations without the action of local dispersion.