• Login
    View Item 
    •   Home
    • Theses & Dissertations
    • 2020 - Mines Theses & Dissertations
    • View Item
    •   Home
    • Theses & Dissertations
    • 2020 - Mines Theses & Dissertations
    • View Item
    JavaScript is disabled for your browser. Some features of this site may not work without it.

    Browse

    All of Mines RepositoryCommunitiesPublication DateAuthorsTitlesSubjectsThis CollectionPublication DateAuthorsTitlesSubjects

    My Account

    Login

    Mines Links

    Arthur Lakes LibraryColorado School of Mines

    Statistics

    Display Statistics

    Numerical and experimental study of soil-atmosphere exchange processes across an undulating soil surface influenced by the near-surface atmospheric boundary layer

    • CSV
    • RefMan
    • EndNote
    • BibTex
    • RefWorks
    Thumbnail
    Name:
    Gao_mines_0052E_12065.pdf
    Size:
    4.610Mb
    Format:
    PDF
    Download
    Thumbnail
    Name:
    supplemental.zip
    Size:
    378.4Mb
    Format:
    Unknown
    Download
    Author
    Gao, Bo
    Advisor
    Smits, Kathleen M.
    Date issued
    2020
    Keywords
    mass and heat transfer
    soil surface roughness
    turbulent flow
    particle image velocimetry
    coupling free flow and porous media flow
    soil-atmosphere interaction
    
    Metadata
    Show full item record
    URI
    https://hdl.handle.net/11124/176310
    Abstract
    Soil-atmosphere exchange processes are critical to a wide range of applications, such as greenhouse gas release to the atmosphere, 222Rn transport into buildings, geothermal heat production, global water cycle and land management, which are closely related to the environmental health and protection, climate change, and energy supply. Given the importance, this research aims to investigate soil-atmosphere exchange processes with a special focus on bare-soil evaporation, a process of mass, momentum, and heat transfer between the soil and the atmosphere, by interweaving experimental and numerical approaches. A critical feature of bare soil involves undulating surfaces due to either natural or manual processes. The near-surface boundary layer is significantly influenced by the surface geometry besides of atmospheric conditions. The combined influence of soil undulations and the near-surface boundary layer results in distinct exchange behaviors compared to a hydrodynamically smooth surface. This topic has not been studied systematically due to the lack of appropriate models and high-fidelity datasets. Therefore, the overarching goal of this research is to advance our understandings of the mass, momentum, and heat transfer between the soil and the atmosphere by including the combined influence of undulating soil surfaces and the corresponding near-surface atmospheric boundary layer to ultimately improve the representation of such processes in hydrological modeling effort. Accordingly, three phases are defined. First, a fundamental study to investigate the undulating-surface evaporation behaviors under a laminar boundary layer was conducted. A fully coupled model describing the mass, momentum, and heat transfer between the soil and the atmosphere was developed and validated through a laboratory experiment using wind tunnel – soil tank system. This model was then used to investigate the influence of atmospheric conditions, soil properties, and soil surface configurations on evaporation. Results demonstrate that soil undulations affect evaporation by influencing the diffusion in the laminar boundary layer and the capillary flow inside the soil, resulting in a heterogeneous distribution of local evaporative flux along the undulating soil surface. Second, the above model was extended by incorporating turbulence and used to investigate undulating-surface evaporation under turbulent airflow. Hot-wire Anemometry was first employed to measure the velocity profiles above the undulating surface. Results confirmed the presence of recirculation zones in the valleys and the corresponding locally low evaporative flux. Turbulent airflow was found to enhance evaporation and the surface configurations affect local evaporation by influencing the vapor distribution and surface water availability, especially as recirculation zones form. As a joint result of turbulence and undulations, the influence of wind speed on the evaporation was restricted. Third, a reduced model concept was adopted from perspectives of applications, which simplifies the soil-atmosphere exchange via a flux top boundary condition based on Monin-Obukhov similarity theory. The vapor roughness length (z0v) and momentum roughness length (z0m) are two major parameters in this model characterizing the mass and momentum transfer between the soil surface and the atmosphere. The relationship between z0v and z0m, and the subsequent aerodynamic resistance were parameterized through direct measurements of the velocity field above the undulating soil surface. Four laboratory experiments with unique design were conducted and Particle Imaging Velocimetry was employed to collect the velocity field information. Results show that z0v is roughly smaller than z0m by 3 to 7 orders of magnitude, owing to the undulating surface and the ratio of z0v to z0m are significantly influenced by the surface configuration and wind speed. The newly formulized aerodynamic resistance was then used to evaluate the evaporation rate for laboratory and field experiments, demonstrating the efficacy of the approach.
    Rights
    Copyright of the original work is retained by the author.
    Collections
    2020 - Mines Theses & Dissertations

    entitlement

     
    DSpace software (copyright © 2002 - 2022)  DuraSpace
    Quick Guide | Contact Us
    Open Repository is a service operated by 
    Atmire NV
     

    Export search results

    The export option will allow you to export the current search results of the entered query to a file. Different formats are available for download. To export the items, click on the button corresponding with the preferred download format.

    By default, clicking on the export buttons will result in a download of the allowed maximum amount of items.

    To select a subset of the search results, click "Selective Export" button and make a selection of the items you want to export. The amount of items that can be exported at once is similarly restricted as the full export.

    After making a selection, click one of the export format buttons. The amount of items that will be exported is indicated in the bubble next to export format.