Browsing by Subject "sediment transport"

Now showing 1 - 8 of 8
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    A bedform tracking tool coupled with Fast Fourier Transform decomposition
    (2021-02-12) Lee, Jiyong; Musa, Mirko; Guala, Michele; lee02291@umn.edu; Lee, Jiyong; Turbulent Boundary Layer plus research team
    Quantifying bedform characteristics is crucial because bedforms are omnipresent and play an important role in fluvial environments. Bedforms induce form drag against flows and can significantly alter water depth, flow velocity, and sediment transport rate (i.e. the hydraulic roughness of channels can be parameterized with bedforms). In addition, ship navigation can be constrained by the presence and distributions of bedform crests; and localized scour within bedform troughs can deteriorate performance of fluvial infrastructures (e.g. containment walls, embedded pipes, or groynes). Despite of its importance, characterizing bedforms has been challenges due to inherent multi-scale features observed in channel bathymetries in both natural rivers and laboratory flumes. To tackle such challenges, we developed a bedform tracking tool coupled with Fast Fourier Transform (FFT) decomposition. A key advantage of the presented bedform tracking method is that bedform characteristics (morphology and kinematics) can be quantified in a wider range of scales.
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    Hydrokinetic turbine array performance and geomorphic effects under different siting strategies and sediment transport conditions: topography, flow velocity and array performance measurements
    (2019-06-27) Musa, Mirko; Hill, Craig; Guala, Michele; mguala@umn.edu; Guala, Michele; Saint Anthony Falls Laboratory, CEGE, University of Minnesota
    Hydrokinetic energy can be extracted efficiently from naturally occurring water flows. Although representing a continuous and ubiquitous source of kinetic energy, rivers in particular are delicate environments, sensitive to external disturbances. Asymmetric installation of in-stream hydrokinetic energy converters have proven to actively interact with sediment transport and bedforms characteristics, triggering non-local geomorphic effects that resemble river instabilities known as forced-bars. This data-set comprises a series of measurements of channel topography evolution, flow velocity around the turbines and array performance under different configurations.
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    Interactions Between Channel Topography and Hydrokinetic Turbines: Sediment Transport, Turbine Performance, and Wake Characteristics
    (2015-08) Hill, Craig
    Accelerating marine hydrokinetic (MHK) renewable energy development towards commercial viability requires investigating interactions between the engineered environment and its surrounding physical and biological environments. Complex and energetic hydrodynamic and morphodynamic environments desired for such energy conversion installations present difficulties for designing efficient yet robust sustainable devices, while permitting agency uncertainties regarding MHK device environmental interactions result in lengthy and costly processes prior to installing and demonstrating emerging technologies. A research program at St. Anthony Falls Laboratory (SAFL), University of Minnesota, utilized multi-scale physical experiments to study the interactions between axial-flow hydrokinetic turbines, turbulent open channel flow, sediment transport, turbulent turbine wakes, and complex hydro-morphodynamic processes in channels. Model axial-flow current-driven three-bladed turbines (rotor diameters, dT = 0.15m and 0.5m) were installed in open channel flumes with both erodible and non-erodible substrates. Device-induced local scour was monitored over several hydraulic conditions and material sizes. Synchronous velocity, bed elevation and turbine performance measurements provide an indication into the effect channel topography has on device performance. Complimentary experiments were performed in a realistic meandering outdoor research channel with active sediment transport to investigate device interactions with bedform migration and secondary turbulent flow patterns in asymmetric channel environments. The suite of experiments undertaken during this research program at SAFL in multiple channels with stationary and mobile substrates under a variety of turbine configurations provides an in-depth investigation into how axial-flow hydrokinetic devices respond to turbulent channel flow and topographic complexity, and how they impact local and far-field sediment transport characteristics. Results provide the foundation for investigating advanced turbine control strategies for optimal power production in non-stationary environments, while also providing a robust data-set for computational model validation for further investigating the interactions between energy conversion devices and the physical environment.
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    Laboratory Studies of Segregation in Prograding Deltas of TSRU tailings
    (2020-12) Widmer, Rochelle
    The largest issue common in the tailings reclamation process used by the oil sands industry today is the slow settling rate of fine particles relative to larger particles. We hypothesize that if the fine and coarse particles were able to somehow settle together that there would be less segregation and therefore the ponds would be more stable. Before this idea can be explored, a greater understanding of the concepts behind the sorting mechanisms is required as well as an examination of the conditions that reduce the amount of sorting. For our experiments, these ideas would be explored by varying the dynamics to allow for more mixing to occur. It is clear that unmixed deposits are undesirable for ponds due to the fact that the fine particles hinder the reclamation process by settling at slower rates and not naturally dewatering. We hypothesize that if some of the fines were to intermix with the coarse particles present on the beaches of the ponds, a stable beach would still be produced. We are hopeful that the methods we investigate in this thesis will assist the industry in identifying the general dynamics present in their deposits and subsequently adjust these dynamics to provide a more desirable outcome.
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    Measurements of spatio-temporal fluvial channel bed evolution and sediment transport rate under four different bedload dominant transport conditions in the SAFL main channel
    (2022-01-03) Lee, Jiyong; Arvind, Singh; Guala, Michele; mguala@umn.edu; Guala, Michele; Turbulent Boundary Layer plus research team
    Accurate prediction of sediment transport rate is important for understanding of fluvial channel evolution. Yet, our understanding on the sediment transport processes is far from clear due to their large spatio-temporal variability, and complex interaction with flow dynamics and channel morphology. Assuming the most of sediment is transported by migrating bedforms, we study how various scales of migrating bedforms contribute to sediment transport. Our experiments suggest that small, secondary ripples on the bed surface emerge as the main contributor to the sediment transport. In addition, we find that the sediment transport rate can be accurately estimated based on spectral descriptions of temporal bed elevation statistics. This data archive includes synchronized three independent measurements under four different bedload dominant transport conditions: volumetric sediment flux time series, bed elevation timeseries at fixed locations, and 2D spatio-temporal bed evolution.
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    The morphodynamic influence of cohesive sediment on coastal systems across scales
    (2016-07) Abeyta, Antoinette
    Cohesive sediment makes up a large portion of the rock record and much of the earth’s surface sediment. Despite how common cohesive sediments are, the focus of research on sedimentary systems has largely been on non-cohesive sediment. Consequently, there has been limited research on how cohesive sediment influences sediment transport and the implications this has for depositional systems. To increase our knowledge of cohesive sediment, it is important to understand the morphological impact of cohesive sediment on depositional systems. Physical experiments provide a powerful tool for approaching this problem as they will allow us to constrain and measure parameters which may be difficult to measure in the field. The overarching goal of this project is to expand our experimental framework to include the use of cohesive sediment, which allows us to investigate an important set of effects in the field. Presented here is a framework of physical experiments, which investigate quantitative aspects of how cohesive sediment influences morphodynamics across scales. The first experimental series investigates how mass failures form in cohesive sediment on delta fronts and what factors influence their occurrence and evolution. The second experimental series is a study on how cohesion influences deltaic processes and overall morphology. Finally, the last experimental series is on how cohesive and other fine sediment lead to changes in the gradient of sediment flux that in turn lead to upstream changes in the overall sediment mass balance in coastal systems.
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    Quantifying Galloway: Fluvial, Tidal and Wave Influence on Experimental and Field Deltas
    (2016-04) Baumgardner, Sarah
    Deltas are some of the most densely settled landscapes on Earth and are of the utmost importance economic and agricultural importance. Human use of these areas is threatened by climate change, and our future management of them will benefit from increased understanding of their response to the energy regimes that shape their planform morphology. We present a series of experiments on experimental deltas in which we study the link between impinging tide and wave energy and measures of delta geometry as well as an application of these metrics to a large dataset of images of deltas in the field.
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    Scaled Hydrokinetic Turbine Array installed in a laboratory channel and flood-like sediment transport conditions: topography, flow velocity and array model performance
    (2019-06-26) Musa, Mirko; Hill, Craig; Sotiropoulos, Fotis; Guala, Michele; mguala@umn.edu; Guala, Michele; Saint Anthony Falls Laboratory, CEGE, University of Minnesota
    The data represent sediment flux, spatio-temporally resolved topographic scans, flow velocity and voltage from the hydrokinetic turbine array experiments presented in the referenced scientific article published on Nature Energy (see reference). Hydrokinetic Energy represents a viable source of renewable energy that harness the kinetic energy of natural currents. Our experiments show that this technology can be deployed efficiently in large sandy rivers (e.g. Mississippi River), without compromising the geomorphic equilibrium of the stream and the structural safety of the turbine foundation, even in the presence of large migrating dunes.