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Browsing by Subject "Experiment"

Now showing 1 - 4 of 4
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    Experimental Investigation of Homogeneous Anisotropic Turbulence
    (2019-07) Carter, Douglas
    Motivated by the need to substantiate the existing literature on homogeneous turbulence with experimental data, a novel zero-mean homogeneous turbulence chamber is presented. Despite the anisotropy of the large scale velocity fluctuations, the experimental apparatus is found to well approximate homogeneous, shear-less turbulence over scales larger than the integral lengths of the flow for four separate cases at Reynolds numbers (based on the Taylor microscale) ranging between 154 and 412. This enables a detailed investigation of the turbulence statistics as obtained by 2D particle image velocimetry, which confirms the existence of inertial scaling ranges in both the second-order structure functions and energy spectra. It is found that the anisotropy of the flow persists down to the smallest scales, though its influence decreases with decreasing scale. The coherent structures, identified using a percolation analysis, are however isotropic in their geometry and generally collapse across cases using the Taylor microscale as a normalization length scale. Two types of scale interaction analyses are applied to the turbulent fields and indicate that there exists substantial coupling between scales small and large; challenging the classic assumption that a range of scales might emerge which is independent of the large scales. Employing the generalized Karman-Howarth-Monin equation in scale space, the energy cascade is found to move energy downscale across all cases, which is also confirmed using a filter space technique. The magnitude of the non-linear energy transfer in scale space is however found to be increasingly anisotropic for increasing large-scale RMS velocity ratio u'_1/u'_2. Using a conditional sampling procedure based on the activity of the small-scales, the non-linear energy transfer is found to have a strong dependence on the relative small-scale activity (as well as the presence of coherent structures), which causes enhanced downscale non-linear energy transfer or upscale non-linear energy transfer of moderate magnitude depending on the subset. In addition to showcasing accurate PIV measurements of homogeneous turbulence over a large range of scales, the results point to the complex nature of the energy cascade in the jet-array driven facility, with simultaneous upscale and downscale transfers at each instant as well as spatially concurrent interactions across all scales of the flow.
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    An Experimental Study of Drainage Network Development by Surface and Subsurface Flow in Low-Gradient Landscapes Raster Datasets
    (2021-09-28) Sockness, Brian G; Gran, Karen B; kgran@d.umn.edu; Gran, Karen B; University of Minnesota - Duluth Earth and Environmental Sciences Department
    The data include raster format elevation measurements and other derived parameters captured from small-scale drainage network development experiments conducted at the University of Minnesota - Duluth. Elevation data were captured as point elevation measurements using a terrestrial lidar unit and converted to raster format digital elevation models at four millimeter resolution via interpolation. The digital elevation models are provided here as 1.) ArcGIS Map Package, 2.) TIFF files, and 3.) JPEG images.
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    Experiments on identity, theft and mitigation strategies.
    (2011-06) Pecenka, Clinton Joseph
    This dissertation uses a series of taking games to examine theft, identity and mitigation strategies.
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    Structural Mechanics Characterization of Steel Intermeshed Connections
    (2020-07) Shemshadian, MohammadEbrahim
    This thesis presents the efforts to develop a new class of steel connection named the “Intermeshed Connection” for gravity load resistance in frame structures. The thesis investigates the performance of the connection system using physical testing and numerical simulation, as well as methods for its design. The project herein lays the groundwork to transform the steel building construction industry by advancing the underlying science and engineering precepts for intermeshed connections created from precise, volumetric cutting. Advanced manufacturing techniques, such as high-definition plasma, water jet, and laser cutting, are powerful tools that offer fast operation and precise finish in the process of steel fabrication. To date, this class of advanced manufacturing equipment has only been used to accelerate traditional processes for cutting sheet metal or other conventional fabrication activities (e.g. cutting instead of drilling holes). Such approaches have not capitalized on the equipment’s full potential. The intermeshed connection is intended to exploit this potential by harnessing advanced cutting technologies for volumetric cutting open steel sections, which results in precise steel pieces that can intermesh (i.e. interlock) with each other and form a connection. In such connections, loads transfer mainly through direct contact of the connection components rather than by traditional means through welds or bolts, which facilitates fast assembly and disassembly of steel structures and material reuse. The intermeshed system, if fully automated, can enhance the integration between design, fabrication, and installation. Although the intermeshed connection has multiple interesting features to offer, the idea of cutting of open steel sections poses challenges regarding the load-transfer mechanisms and failure modes for intermeshed connections. For instance, implementation of the cuts would cause discontinuity in the beam or formation of sharp corners in the specimen. The former could interrupt load paths, and the latter could increase stress concentrations. Therefore, to introduce the intermeshed connection system to engineering practice, the structural behavior of these connections needs to be fully understood and adequate performance under gravity loads needs to be demonstrated. The aim of the present study is to provide insight on the structural performance of the intermeshed connection at both global and local levels, and to investigate appropriate design methods. To reach this goal, numerous details of the intermeshed connection were considered, a design procedure was developed, physical specimens were designed and tested, and beams with intermeshed connections were analyzed using sophisticated numerical procedures. This investigation was conducted in a step-by-step state assessment of the intermeshed connection subjected to multiple scenarios of gravity loading and various support conditions. Load resistance and design of these connections were explored to evaluate the mechanics of intermeshed connections including stress and strain concentrations, effective material utilization, failure modes, and connection geometry optimization. Relying on the interaction of individual components, the intermeshed connection demonstrates ample load carrying capacity, stiffness, and ductility, which fulfilled the design requirements. This connection promises to be robust, secure, dismountable and offers the ability to be manufactured within current industrial tolerances and be erected quickly.