Browsing by Author "Turbulent Boundary Layer plus research team"
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Item 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 teamQuantifying 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.Item 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 teamAccurate 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.Item Measurements of spatio-temporal fluvial channel bed evolution in an array of yawed porous vanes at the Saint Anthony Falls Laboratory (SAFL) main channel(2024-04-11) Lee, Jiyong; Tseng, Chien-Yung; Musa, Mirko; Guala, Michele; mguala@umn.edu; Guala, Michele; Turbulent Boundary Layer plus research teamControlling lateral sediment flux and bed surface elevation distributions is important engineering solutions for sustainable river management. However, quantification of the lateral sediment flux has posed great challenges for river engineers for decades due to difficulties in measuring high resolution 2D spatio-temporal bed surface evolution data, \eta(x,y,t), when lateral sediment flux control is imposed by hydraulic structures. Here, \eta is bed surface elevation. Dimensions x and y are stream- and span-wise directions, and t is time. We conducted two sets of open channel experiments, in which \eta(x,y,t) was monitored using the state-of-the-art laser scanning data acquisition system. The first experiment was carried out without hydraulic structures, namely baseline case. The second experiment was conducted under the same hydraulic condition with an array of yawed porous vanes that were installed at the one-half of the channel width, imposing asymmetric lateral sediment flux. By comparing results from these two sets of experiments, the effects of an array of yawed porous vanes on the lateral sediment flux were quantified. We found that an array of porous yawed vanes can effectively direct sediment flux in the lateral direction by 9-18% of the averaged streamwise sediment flux under the current array configurations and hydraulic conditions.