Scholarship & Research
Permanent URI for this communityhttps://scholarworks.montana.edu/handle/1/1
Browse
5 results
Search Results
Item Characterization of the effects of hygrothermal-aging on mechanical performance and damage progression of fiberglass epoxy composite(Montana State University - Bozeman, College of Engineering, 2018) Voth, Michael Mark; Chairperson, Graduate Committee: David A. MillerMarine Hydro-Kinetic Devices (MHK) are a developing renewable energy technology that allows energy to be harvested from the natural flow of water due to tides, currents, and waves. Fiber Reinforced Polymers (FRP), which have been extensively used in wind energy applications, offer favorable mechanical properties as well as low costs and manufacturability making them a viable option for construction of MHK devices. However, exposure to a harsh marine environment results in moisture uptake into the FRP, often degrading mechanical properties. A study of a fiberglass-epoxy FRP was conducted to characterize the effects of moisture on mechanical properties and damage behavior of the material as well as classify the degradation mechanisms responsible for changes in performance. Environmental exposure was simulated through hygrothermal aging, exposing the FRP samples to distilled water and elevated temperature (50 °C) to accelerate the environmental effects. Quasi-static tension tests of both unidirectional and cross-ply laminates were conducted to classify the effects of moisture on mechanical properties of constituent and multi-angle laminates. Cross-ply laminates experienced 54% reduction in strengths due to moisture absorption, while unidirectional laminates strengths were reduced by 40%. Constitutive stress-strain response in conjunction with Acoustic Emission (AE) monitoring describe changes in damage behavior due to hygrothermal aging. This work also characterizes hygrothermal effects on pure/neat epoxy material to aid in interpreting hygrothermal degradation mechanisms in the composite as well as guided ultrasonic evaluation of composite specimens to characterize effects of moisture on AE signals.Item Evaluation of pitch control techniques for a cross-flow water turbine(Montana State University - Bozeman, College of Engineering, 2017) Gauthier, Timothy Andrew; Chairperson, Graduate Committee: Erick JohnsonCross-flow water turbines are complex devices that have yet to see large-scale implementation relative to conventional horizontal-axis wind turbines. While wind energy was the primary target of past investigations, water energy follows most of the same dynamic principles. However, water currents tend to be much more stable than their wind current counterparts, and many water currents exist in channels that favor the compact shape of the cross-flow turbine. These advantages have rejuvenated interest in cross-flow turbine design for marine energy generation. Computational models give engineers the ability to accurately estimate what designs work best to avoid costly field maintenance and downtime. Specifically, computational fluid dynamics uses the Navier-Stokes equations, a set of differential equations that describe the pressure and velocity fields in a fluid domain. The Reynold-Averaged Navier-Stokes turbulence model described in this work examines how controlling the pitch of water turbine blades can improve system performance and reliability. Pitch means that the blade noses up or down about the chord line which runs from leading edge to trailing edge relative to the inflow. Pitch control was originally developed for helicopter blades and is commonly used by conventional wind turbines, but pitch control for water turbines is a relatively new research area. Initial results suggest significant incremental gain in power output with pitch control up to 149%, as compared to a no-pitch case, based on a to-scale representation of the cross-flow water turbine in the Fluids and Computations Laboratory at Montana State University. Simultaneous reliability gain is observed as the force transmitted by the water to the blades is reduced by 135%; this may allow for lower cost turbine structures and streamlined hydrofoil design. Additionally, turbine wake profile visualization and blade pressure coefficient curves describe the viscous interaction both quantitatively and qualitatively. Cross-flow water turbines have the potential to become a significant worldwide energy source, with performance optimization studies such as these a necessary prerequisite.Item Acoustic propagation modeling for marine hydrokinetic applications(Montana State University - Bozeman, College of Engineering, 2016) Johnson, Charles Nathan; Chairperson, Graduate Committee: Erick JohnsonThe combination of riverine, tidal, and wave energy have the potential to supply over one third of the United States' annual electricity demand [1]. However, in order to deploy and test prototypes and commercial installations, marine hydrokinetic (MHK) devices must meet strict regulatory guidelines. These regulations mandate the maximum amount of noise that can be generated and sets particular thresholds for determining disturbance and injury caused by noise. In the absence of measured levels from in-situ deployments, a model for predicting the propagation of a MHK source in a real hydroacoustic environment needs to be established. An accurate model for predicting the propagation of a MHK source(s) in a real-life hydro-acoustic environment has been established. This model will help promote the growth and viability of marine, water, and hydrokinetic energy by confidently assuring federal regulations are meet and harmful impacts to marine fish and wildlife are minimal. A 3D finite-difference solution to the governing velocity-pressure equations is presented and offers advantages over other acoustic propagation techniques for MHK applications as spatially varying sound speeds, bathymetry, and bed composition that form complex 3D interactions can be modeled. This solution method also allows for the inclusion of complex MHK sound spectra from turbines and/or arrays of turbines. A number of different cases for hydro-acoustic environments have been validated by both analytical and numerical results from canonical and benchmark problems. Several of these key validation cases are presented in order to show the applicability and viability of a finite difference numerical implementation code for predicting acoustic propagation in a hydro environment. With the model successfully validated for hydro-acoustic environments, more complex and realistic MHK sources from turbines and/or arrays can be modeled. A systematic investigation of MHK relevant scenarios is presented with increasing complexity including a single- and multi- source investigation, a random phase change study, and a hydro-acoustic model integrationItem Bathymetric effects on marine hydrokinetic array performance(Montana State University - Bozeman, College of Engineering, 2015) Peebles, Garrett William; Chairperson, Graduate Committee: Erick JohnsonApproximately 16% of the globally generated electricity comes from conventional hydropower installations. Recent technological improvements in marine hydrokinetics (MHK), and a global demand for increased renewable energy, are enabling this technology to become a major contributor in the global energy market. MHK devices convert the kinetic energy, or energy of motion, from waves or water currents into electricity that is then transferred to the electrical grid. Wave energy converters (WECs) capitalize on the oscillatory motion of ocean waves, while current energy converters (CECs) use river, tidal, or ocean currents to generate electricity and often resemble wind turbines. Unlike wind, water currents are less intermittent, and, in the case of tidal currents, highly predictable. At present scales, individual CEC and WEC devices alone are not powerful enough to make hydrokinetic power economically feasible. Therefore, deployment of arrays of marine hydrokinetic devices is the most cost-effective method for these devices to become a major contributor in the energy market. In addition to device design and operational conditions, how these devices are deployed within a site determines their potential for power generation. The power generated depends upon interdevice proximity, where it is generally assumed more electricity is generated as the spacing between each device increases. However, most array performance studies of current-energy converters do not consider bed topography and are either inside smooth walled channels or deep, open waters. The research presented here explores the impact of site bathymetry on array performance since each deployment location is likely to have a significant impact on the optimality of an array layout. It is first shown that without boundary constraints the performance of an array does improve as the inter-device spacing is increased. Uniquely though, the normalized power and loading on an array is not transferable from an unconstrained domain to simple, sloping beds. The effects of this demonstrate the need to consider the topography of real world locations for general array designs.Item Simulation of irrigation and reservoir water use in the Canyon Ferry drainage basin(Montana State University - Bozeman, College of Engineering, 1987) DeLuca, Denise Kelley