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Description
In this work, the hydrodynamics of Suction Stabilization is studied. Suction stabilization was found to stabilize floating platforms/floats in a much better way as compared to the conventional methods. This was achieved by an effective increment in the metacentric height due to the Inverse Slack Tank (IST) effect. The study involves the analysis of the existing designs and optimizing its performance. This research investigates the stability of such floats and the hydrodynamic forces acting on the same for offshore applications, such as wind turbines. A simple mathematical model for the condition of parametric resonance is developed and the results are verified, both analytically and experimentally.
ContributorsCherangara Subramanian, Susheelkumar (Author) / Redkar, Sangram (Thesis advisor) / Rajadas, John (Committee member) / Rogers, Bradley (Committee member) / Arizona State University (Publisher)
Created2014
Description
Filtration for microfluidic sample-collection devices is desirable for sample selection, concentration, preprocessing, and downstream manipulation, but microfabricating the required sub-micrometer filtration structure is an elaborate process. This thesis presents a simple method to fabricate polydimethylsiloxane (PDMS) devices with an integrated membrane filter that will sample, lyse, and extract the DNA from microorganisms in aqueous environments. An off-the-shelf membrane filter disc was embedded in a PDMS layer and sequentially bound with other PDMS channel layers. No leakage was observed during filtration. This device was validated by concentrating a large amount of cyanobacterium Synechocystis in simulated sample water with consistent performance across devices. After accumulating sufficient biomass on the filter, a sequential electrochemical lysing process was performed by applying 5VDC across the filter. This device was further evaluated by delivering several samples of differing concentrations of cyanobacterium Synechocystis then quantifying the DNA using real-time PCR. Lastly, an environmental sample was run through the device and the amount of photosynthetic microorganisms present in the water was determined. The major breakthroughs in this design are low energy demand, cheap materials, simple design, straightforward fabrication, and robust performance, together enabling wide-utility of similar chip-based devices for field-deployable operations in environmental micro-biotechnology.
ContributorsLecluse, Aurelie (Author) / Meldrum, Deirdre (Thesis advisor) / Chao, Joseph (Thesis advisor) / Westerhoff, Paul (Committee member) / Arizona State University (Publisher)
Created2011
Description
In the marine ecosystem, mangrove forests protect the coastline due to their unique prop root system functions as a natural barrier to stabilize sediment and mitigate erosion. Such distinct characteristics provide a design inspiration to reduce local scour around underwater foundation systems such as the monopile foundation of offshore wind turbines. In this study, a ring of skirt piles in a circular layout inspired by the mangrove root structure has been proposed which aims to protect the centered monopile foundation. Three main aspects of the mangrove prop root system have been extracted to investigate the scour mitigation effect from the hydraulic, geotechnical, and bio-cementation perspectives. Laboratory flume tests have been conducted to evaluate the anti-scour potential using the proposed skirt pile groups. 3D reconstruction using the photogrammetric method has been employed to reconstruct the scoured bed for quantitative analysis. Computational fluid dynamics (CFD) and discrete element method (DEM) simulations have been performed to investigate the pile-flow and pile-sediment interactions, respectively. Results indicate the proposed skirt pile group reduces the scour depth and the volume of the scour hole by up to 57% and 85%, respectively. DEM simulation implied the installation of skirt piles demonstrates not only hydraulic but also geotechnical benefits due to the soil plug effect. In addition, a reactive transport model framework that simulates the bio-grouting process using microbially induced calcite precipitation (MICP) via shallow underwater injection has been developed to model the key processes such as bacterial attachment and detachment, urea hydrolysis, and calcite precipitation. The simulated cementation distribution exhibits a decent agreement with the experimental results, which could potentially be served for strategic optimization before conducting large or field-scale underwater injection tests. The model framework has been incorporated to simulate the MICP injection using skirt piles. Preliminary findings from this study demonstrated the feasibility of using mangrove-inspired skirt piles to mitigate scour for underwater foundation systems.
ContributorsLi, Xiwei (Author) / Tao, Junliang JT (Thesis advisor) / van Paassen, Leon LVP (Committee member) / Kavazanjian, Edward EK (Committee member) / Arizona State University (Publisher)
Created2024