A. James Clark School of Engineering
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The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item Microbial Induced Corrosion in Oil Pipelines(2020) Farzaneh, Azadeh; Al-Sheikhly, Mohamad MA; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Crude oil pipeline failure due to corrosion processes is a global issue with detrimental effects on the environment and economy. More than 10,000 oil spills occur in the United States alone, each year. These oil spills are so prevalent that they have become the rule rather than being a 1-time incident. Many of these oil spills happen as a result of pipeline failure due to corrosion. Microbial-Induced Corrosion (MIC) accounts for 20% of the total number of pipeline corrosion incidents. Therefore, the mechanisms involved and especially in the case of microbial corrosion must be studied and elucidated.Sulfate-Reducing Bacteria (SRB) are the main culprits of MIC. The first suggested mechanism in 1930’s related high corrosion rates in buried pipelines to SRB hydrogen utilization and depolarization of the cathodic area on the metal surface. Despite its numerous flaws, it remained the most widely accepted mechanism of MIC. In 2004, a new mechanism called direct electron uptake was suggested for MIC. It related corrosivity of bacteria to direct electron uptake from metallic iron. This mechanism is not fully understood hitherto. Only a few bacteria have been isolated so far that demonstrated direct electron uptake capabilities. Most of the research has been focused on these few isolates. However, if direct-electron uptake is the main MIC mechanism, other SRB strains should possess similar capabilities. This work investigated the possibility of direct electron uptake as the main MIC mechanism for SRB D. bastinii, which has not been studied before, and D. vulgaris, an organotrophic SRB. Both are common bacteria existing in crude oil pipelines. Studies including electrochemical measurements, immersion corrosion testing, metal surface monitoring via scanning electron microscope revealed direct-electron uptake capabilities for both strains. SRB strains were tested under 18 different environmental conditions. Extremely high cathodic current densities were observed in SRB cultures confirming electron transfer from the iron surface to bacteria cells. Finally, based on the large experimental dataset provided in this work, an artificial neural network model was developed to predict MIC. This model demonstrates high correlation coefficients comparable or higher than existing models for general corrosion prediction in the literature. Revealing the predominant mechanisms of MIC along with modeling capabilities enables us to design appropriate measures to eradicate pipe failure due to MIC. Additionally the investigated direct electron uptake ability of the specific SRB strains studied can be used in microbial fuel cells for enhancing the efficiency of biocathodes.Item Photogrammetric Reconstruction of Tandem-Wing Kinematics for Free-Flying Dragonflies Undergoing a Range of Flight Maneuvers(2017) Gabryszuk, Mateusz; Laurence, Stuart J; Aerospace Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Photogrammetric methods are used to reconstruct the body and wing kinematics of free-flying dragonflies. A novel experimental setup was designed and constructed to allow for repeated untethered flights in a constrained flight arena. Kinematic data are presented for twelve individual flights and a total of 23 complete wing strokes, including unaccelerating, accelerating, climbing, and turning flight. High variability is observed in the wing motions employed by individual dragonflies, particularly in terms of stroke amplitude, pitch angle, and wingbeat frequency. Forewing and hindwing flapping is found to be neither in phase nor fully out of phase across all cases, with the forewings lagging the hindwings by an average of 90 degrees. Downstroke durations are observed to be shorter than upstroke durations except in highly accelerating flights. Migratory dragonflies are found to exhibit notably different wing kinematics than non-migratory species.Item The Fluid Dynamics of Mayfly Naiads(2014) Abdelziz, Khaled Mohamed-Refaat; Kiger, Kenneth T; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)During their aquatic phase, mayflies Centroptilum triangulifer use a series of tracheal gills to facilitate gas exchange. Recent experimental studies on nymphal mayflies have identified two coupled features associated with the ontogenic progression of their ventilatory kinematics: 1) there is an abrupt shift from a rowing mechanism in small instars to a flapping mechanism in larger instars, and 2) the flapping mechanism is associated with the development of a flexural hinge that permits the passive movement of a distal flap. The primary role of the tracheal gills is tied to ventilation rather than locomotion. As such, it is not yet understood why such a transition happens and which performance metric is improved, if any. Hence, the goal of the current research is to investigate both features using numerical simulations. First, a computational model of the mayfly is built from a dissected animal. Then, a 3-level prescribed kinematic chain is introduced to a previously in-house developed and in-house validated explicit parallel Navier-Stokes solver where both the advective and diffusive terms are advanced explicitly using a third-order, low-storage, Runge-Kutta scheme. Finally, an immersed boundary method based on a moving least squares reconstruction is implemented to enforce the correct moving boundary conditions. Two different parametric spaces are constructed. The first one investigates the transition from rowing to flapping kinematics, the morphological effects on the flow field and on the proposed performance parameters while the second aims to provide an explanation for the hinge development. Two metrics based on control volume analysis are proposed to quantify the performance of each numerical case. The first metric is simply the mechanical efficiency of the energy transfer from the moving gills to the surrounding flow field while the second incorporates the mass flow rate across the control surface. The second metric is promising because it is able to provide a plausible explanation of both features by showing that the rate of work done by the mayfly is diminished throughout ontogeny with respect to the induced mass flow rate.