Damping of Sinusoidal Surface Flux Fluctuations with Soil Depth
Damping of Sinusoidal Surface Flux Fluctuations with Soil Depth
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DOI：
10.2136/vzj2008.0084
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发表时间：
2009-02
影响因子：
2.8
通讯作者：
M. Bakker;J. Nieber
中科院分区：
文献类型：
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作者：
M. Bakker;J. Nieber
土壤表面通量的正弦波动随包气带深度的增加而减弱，因此超过一定深度后，水流可近似为稳定的。为了研究随深度的阻尼，我们开发了一个新的解析解垂直周期性流在包气带，在土壤表面指定的正弦通量。该解决方案是基于使用的Gardner-Kozeny模型的水力传导率和土壤水分和线性化的扩散和对流项的控制微分方程。给出了通量随深度衰减的特征长度。在三倍于特征长度的深度处，通量的振幅减小到表面值的5%。我们比较了基于四种参考土壤的16种土壤的原始非线性微分方程的解析解和有限元解，使用土壤表面蒸发和渗透的每日正弦循环。对于所研究的土壤和环境，与有限元解相比，解析解在土壤剖面的任何深度处都能产生合理的阻尼因子值。当波动（幅度和周期）较小时，解更准确。当表面通量被写为傅立叶级数时，所提出的解可用于一维入渗的一般情况。
Sinusoidal fluctuations of the flux at the soil surface dampen with depth in the vadose zone such that beyond a certain depth, flow may be approximated as steady. To investigate the damping with depth, we developed a new analytic solution for vertical periodic flow in the vadose zone, with a sinusoidal flux specified at the soil surface. The solution is based on the use of the Gardner–Kozeny model for hydraulic conductivity and soil moisture and on a linearization of the diffusive and advective terms in the governing differential equation. A characteristic length is presented for the damping of the flux with depth. At a depth of three times the characteristic length, the amplitude of the flux had reduced to 5% of the value at the surface. We compared the analytic solution to finite‐element solutions of the original, nonlinear differential equation for 16 soils based on four reference soils, using a daily sinusoidal cycling of evaporation and infiltration at the soil surface. For the soils and circumstances investigated, the analytic solution produced reasonable values of the damping factor at any depth in the soil profile compared with the finite‐element solutions. The solution is more accurate when the fluctuations (both amplitude and period) are smaller. The presented solution may be used for general cases of one‐dimensional infiltration when the surface flux is written as a Fourier series.