Experimental and Numerical Study of Evaporation From Wavy Surfaces by Coupling Free Flow and Porous Media Flow

Gao, Bo; Davarzani, Hossein; Helmig, Rainer; Smits, Kathleen M.

doi:10.1029/2018wr023423

Cited by 14 publications

(32 citation statements)

References 62 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For example, when one imagines a tilled field, it is more likely that the surface has some undulations and is in general rather rough. Verma and Cermak (1974), Haghighi and Or (2015), and Gao et al (2018) investigate surface undulations and their effect on evaporation rates, omitting the influence of radiation. Key findings are that surface undulations can lead to both higher or lower evaporation rates compared to a flat surface, highlighting the complexity of soil-water evaporation from nonflat surfaces.…”

Section: Surface Undulationsmentioning

confidence: 99%

Influence of Radiation on Evaporation Rates: A Numerical Analysis

Heck

Coltman

Schneider

et al. 2020

Water Resources Research

Self Cite

View full text Add to dashboard Cite

We present a fully coupled soil-atmosphere model that includes radiation in the energy balance of the coupling conditions between the two domains. The model is able to describe evaporation processes under the influence of turbulence, surface roughness, and soil heterogeneities and focuses specifically on the influence of radiation on the mass and energy transport across the soil-atmosphere interface. It is shown that evaporation rates are clearly dominated by the diurnal cycle of solar irradiance. During Stage-I evaporation maximum temperatures are regulated due to evaporative cooling, but after a transition into Stage-II evaporation, temperatures rise tremendously. We compare two different soil types, a coarser, sandy soil and a finer, silty soil, and analyze evaporation rates, surface temperatures, and net radiation for three different wind conditions. The influence of surface undulations on radiation and evaporation is analyzed and shows that radiation can lead to different local drying patterns in the hills and the valleys of the porous medium, depending on the height of the undulations and on the direction of the Sun. At last a comparison of lysimeter measurement data to the numerical examples shows a good match for measured and calculated radiation values but evaporation rates are still overestimated in the model. Possible reasons for the discrepancy between measurement and model data are analyzed and are found to be uncertainties about the parameters close to the interface, which are decisive for determining evaporation rates. Several models are available that are able to describe evaporation with different levels of complexity, especially regarding simplifications made for the coupling conditions between the soil and the atmosphere.

show abstract

Section: Surface Undulationsmentioning

confidence: 99%

Influence of Radiation on Evaporation Rates: A Numerical Analysis

Heck

Coltman

Schneider

et al. 2020

Water Resources Research

Self Cite

View full text Add to dashboard Cite

show abstract

“…In our previous study, Gao et al (2018) developed a twodomain model at the representative element volume (REV) scale to estimate evaporation by coupled Navier-Stokes free flow and porous media Darcy flow with appropriate coupling conditions at the free flow-porous media interface. This model describes the full nonequilibrium mass, momentum, and heat transfer processes in the whole evaporation system with undulating soil surfaces under laminar conditions and has been validated with corresponding laboratory experimental data (Gao et al, 2018). Compared with the topboundary-condition type formulas, this model avoids many parameterized variables and conditions, thereby excluding much of the uncertainty caused by parameterization.…”

Section: Extension Of Coupled Free Flow and Porous Media Flow Modelmentioning

confidence: 99%

“…Based on these assumptions, a set of equations describing the fluid flow, vapor transport, and heat transfer is defined separately in the free flow and porous media. This mathematical model was discussed in detail in Gao et al (2018). Only the extended part (i.e., the description of turbulent airflow and the change of interfacial conditions due to turbulence) is introduced below.…”

Section: Extension Of Coupled Free Flow and Porous Media Flow Modelmentioning

confidence: 99%

See 1 more Smart Citation

Evaporation from undulating soil surfaces under turbulent airflow through numerical and experimental approaches

Gao

Farnsworth

Smits

2020

Vadose Zone Journal

Self Cite

View full text Add to dashboard Cite

Evaporation from undulating soil surfaces is rarely studied due to limited modeling theory and inadequate experimental data linking dynamic soil and atmospheric interactions. The goal of this paper is to provide exploratory insights into evaporation behavior from undulating soil surfaces under turbulent conditions through numerical and experimental approaches. A previously developed and verified coupled free flow and porous media flow model was extended by incorporating turbulent airflow through Reynolds-averaged Navier-Stokes equations. The model explicitly describes the relevant physical processes and the key properties in the free flow, porous media, and at the interface, allowing for the analysis of coupled exchange fluxes. An experiment aiming to simultaneously collect the data of the boundary layer and soil evaporation in the area around the soil-atmosphere interface was conducted using a wind tunnel integrated with a soil tank. The turbulent boundary layer above the undulating soil surface was captured using high-resolution hot-wire anemometry, confirming the presence of recirculation zones in the undulating valleys and locally low evaporative flux. Experimental data were used to validate the extended model, and modeling results demonstrate that turbulent airflow enhances evaporation and shortens the duration of Stage I. The surface geometry significantly affects the local evaporative flux by influencing the vapor distribution, concentration gradient, and water availability at the soil surface, especially when recirculation zones form in the valleys. As a joint result of turbulence and surface undulations, the influence of wind speed on both the local and system-level evaporation rate is restricted.

show abstract

“…If a surface exhibits curvature and undulations or is covered in porous or impermeable obstacles, the formation of sublayers at the surface will change significantly as flow structures will develop, complicating energy and mass transport. Evaporation from surface undulations and around flow obstacles has been investigated experimentally in Verma and Cermak (1974), Haghighi and Or (2015a), Haghighi and Or (2015b), Gao et al (2018), Trautz et al (2018), and Gao et al (2020). These experimental works have further compared their results to numerical models based on surface renewal theory (Haghighi and Or 2015b), or by evaluating either a single flow domain (Trautz et al 2019), or both (Gao et al 2020).…”

Section: Introductionmentioning

confidence: 99%

Obstacles, Interfacial Forms, and Turbulence: A Numerical Analysis of Soil–Water Evaporation Across Different Interfaces

et al. 2020

Self Cite

View full text Add to dashboard Cite

Exchange processes between a turbulent free flow and a porous media flow are sensitive to the flow dynamics in both flow regimes, as well as to the interface that separates them. Resolving these complex exchange processes across irregular interfaces is key in understanding many natural and engineered systems. With soil-water evaporation as the natural application of interest, the coupled behavior and exchange between flow regimes are investigated numerically, considering a turbulent free flow as well as interfacial forms and obstacles. Interfacial forms and obstacles will alter the flow conditions at the interface, creating flow structures that either enhance or reduce exchange rates based on their velocity conditions and their mixing with the main flow. To evaluate how these interfacial forms change the exchange rates, interfacial conditions are isolated and investigated numerically. First, different flow speeds are compared for a flat surface. Second, a porous obstacle of varied height is introduced at the interface, and the effects the flow structures that develop have on the interface are analyzed. The flow parameters of this obstacle are then varied and the interfacial exchange rates investigated. Next, to evaluate the interaction of flow structures between obstacles, a second obstacle is introduced, separated by a varied distance. Finally, the shape of these obstacles is modified to create different wave forms. Each of these interfacial forms and obstacles is shown to create different flow structures adjacent to the surface which alter the mass, momentum, and energy conditions at the interface. These changes will enhance the exchange rate in locations where higher velocity gradients and more mixing with the main flow develop, but will reduce the exchange rate in locations where low velocity gradients and limited mixing with the main flow occur.

show abstract

Experimental and Numerical Study of Evaporation From Wavy Surfaces by Coupling Free Flow and Porous Media Flow

Cited by 14 publications

References 62 publications

Influence of Radiation on Evaporation Rates: A Numerical Analysis

Influence of Radiation on Evaporation Rates: A Numerical Analysis

Evaporation from undulating soil surfaces under turbulent airflow through numerical and experimental approaches

Obstacles, Interfacial Forms, and Turbulence: A Numerical Analysis of Soil–Water Evaporation Across Different Interfaces

Contact Info

Product

Resources

About