Experimental and Numerical Study of Evaporation From Wavy Surfaces by Coupling Free Flow and Porous Media Flow
Experimental and Numerical Study of Evaporation From Wavy Surfaces by Coupling Free Flow and Porous Media Flow
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DOI：
10.1029/2018wr023423
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发表时间：
2018-11
影响因子：
5.4
通讯作者：
B. Gao;H. Davarzani;R. Helmig;K. Smits
中科院分区：
文献类型：
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作者：
B. Gao;H. Davarzani;R. Helmig;K. Smits
土壤表面的宏观粗糙度对蒸发过程中地下与大气之间的质量/能量相互作用有显着影响。然而，大多数以前的作品只考虑从平坦表面的蒸发行为。基于实验和数值模拟的方法，这项工作的目标是提供一个框架，从不规则的土壤表面蒸发的代表性的基本体积尺度的机制的理解。建立了描述非等温条件下蒸发过程的自由流-多孔介质耦合流动模型。为简单起见，考虑正弦型波状表面。为了验证这种建模方法，使用开口风洞和土壤槽进行了实验。该实验系统装有各种环境传感器，以连续收集大气和地下数据。结果表明，表面粗糙度直接影响大气和扩散主导的阶段I和II蒸发行为，分别。大气条件直接影响第一阶段的边界层。蒸发速率由边界层中的扩散决定，而不是由多孔介质中的扩散决定。土壤性质对毛管流有着内在的影响，决定着蒸发量。毛细作用和边界层之间的复杂相互作用导致蒸发通量的不均匀分布和波动（即，沿着土壤表面的位置）和时间。此外，更多和更陡的波指示来自毛细流动的更多影响，与具有相同波幅的单波系统相比增强蒸发，而更陡的波也导致更厚的边界层并减弱蒸发。
The macroscale roughness of the soil surface has significant influences on the mass/energy interactions between the subsurface and the atmosphere during evaporation. However, most previous works only consider evaporation behavior from flat surfaces. Based on experimental and numerical approaches, the goal of this work is to provide a framework for the understanding of the mechanisms of evaporation from irregular soil surfaces at representative elementary volume scale. A coupling free flow‐porous media flow model was developed to describe evaporation under nonisothermal conditions. For simplicity, sinusoidal‐type wavy surfaces were considered. To validate this modeling approach, an experiment using an open‐ended wind tunnel and soil tank was conducted. The experimental system was instrumented with various environmental sensors to continuously collect atmospheric and subsurface data. Results demonstrate that the surface roughness directly affects both atmospheric and diffusion‐dominated stages I and II evaporation behavior, respectively. The atmospheric conditions directly affect the boundary layer during stage I. The evaporation rate is determined by the diffusion in the boundary layer, but not that in the porous media. The soil properties exert intrinsic influence on the capillary flow and determine the evaporation amount. The complex interaction between capillarity and the boundary layer leads to a heterogeneous distribution of evaporative flux with undulation (i.e., location along the soil surface) and time. Additionally, more and steeper waves indicate more influence from capillary flow, enhancing evaporation compared to a single wave system with the same wave amplitude, while steeper waves also result in a thicker boundary layer and weaken evaporation.