Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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Item Underwater acoustic propagation modeling and utilization for marine hydrokinetic devices(Montana State University - Bozeman, College of Engineering, 2024) Hafla, Erin Christine; Chairperson, Graduate Committee: Erick JohnsonOver the last two decades, there has been growing concern surrounding the increase in underwater anthropogenic sounds as expanding human populations interact with marine life and look for alternative energy production methods. That concern has led to a significant push worldwide to understand how propagated sound interacts with the surrounding marine environment. Marine hydrokinetic (MHK) devices are an alternative source of renewable energy available, which generate electricity from the motion of tidal and ocean currents, as well as ocean waves. Sounds produced by MHKs tend to overlap the frequency range common to both marine fauna communication and behavior. Preliminary measurements indicate that sound level values fall near the total sound decibel limitations presented by regulatory bodies. To date, the power optimization of MHK arrays has been prioritized over how its sound is produced, directed, and may impact the marine soundscape. There is a gap in knowledge regarding how marine fauna may respond to these sounds and what their physical and behavioral impact may be, and an absence in measured levels from insitu MHK deployments. A model for predicting the propagation of sound from an array of MHK sources in a real environment is essential for understanding potential impacts on a surrounding system. This work presents a fully three-dimensional solution to a set of coupled, linearized velocity-pressure equations in the time-domain as applied to underwater systems, and is an alternative sound propagation model to the Helmholtz and wave equation methods. The model is validated for a single source located within a series of increasingly complex two-dimensional and three-dimensional shallow water environments and compared against analytical solutions, examples from literature, and recorded sound pressure levels collected from Sequim Bay, WA. An uncertainty analysis for an array of MHK devices is presented to further understand how multiple turbine signals interact with one another in increasingly complex systems. This research presents a novel use of the velocity-pressure equations to analyze the variability associated with sound sources as sound propagates through a selected environment to inform the design and deployment of a MHK device or array of devices to minimize potential future impacts.Item A continuum mixture theory with an application to turbulent snow, air flows and sedimentation(Montana State University - Bozeman, College of Engineering, 1986) Decker, Rand AlanItem Modeling fish passage and energy expenditure for American shad in a steeppass fishway using a computational fluid dynamics model(Montana State University - Bozeman, College of Engineering, 2014) Plymesser, Kathryn Elizabeth; Chairperson, Graduate Committee: Joel CahoonThe Alaska steeppass is a fishway used extensively in the eastern U.S. and in remote locations. The baffles in the steeppass fishway tend to reduce water velocity to magnitudes negotiable by many species. A computational fluid dynamics (CFD) model was developed for common combinations of fishway slope and head pond elevation. Three-dimensional hydraulics information from the CFD model was used as a basis to predict passage success for American shad in the steeppass. The passage model considered six unique algorithms for swim path during ascent, and both the optimal swim speed approach of Castro-Santos (2005) and newly developed swim-speed information based on the laboratory study of Haro, Odeh, Castro-Santos, and Noreika (1999). The passage model was incorporated into a Monte Carlo framework to facilitate robust comparisons between the passage success predicted by the model and the experimental observations of Haro, Odeh, Castro-Santos, and Noreika (1999). The methods of Webb (1975) and Belke (1991) were then adapted to develop predictions of the energy expenditure of American shad. Findings included the observation that fish in the laboratory study did not tend to utilize the distance-optimizing prolonged swim speed of Castro-Santos (2005), but instead travelled at a faster velocity (more similar to the distance-optimizing burst speed) that resulted in significantly lower energy expenditures. The passage model did not indicate that the steeppass fishway presented a substantial velocity challenge to American shad. Comparisons of the passage model results with passage success in the study by Haro, Odeh, Castro-Santos, and Noreika (1999) led to the observation that other hydraulic factors (such as turbulence) or volitional issues should be the subject of further studies. The passage model was reformulated, creating a conceptual fishway of infinite length, to examine the distance at which model fish fail due to fatigue. The infinite-length model predicted that a fishway of 25 feet in length passed 99.0% of fish without fatigue failure. The velocity distributions from the CFD models also suggested that the zones of low velocity that existed near the bottom of the fishway under high head conditions may be desirable for successful ascent.