Engineering Commons^™

Transformation Of Nonlinear Waves In The Presence Of Wind, Current, And Vegetation, Haifei Chen

Electronic Theses and Dissertations

Accurate prediction of extreme wave events is crucial for the safe maritime activities and offshore operations. Improved knowledge of wave dissipation mechanisms due to breaking and vegetation leads to accurate wave forecast, protecting life and property along the coast. The scope of the thesis is to examine the wave transformations in the presence of wind, current, and vegetation, using a two-phase flow solver based on the open-source platform OpenFOAM. The Reynolds-Averaged Navier-Stokes (RANS) equations are coupled with a Volume of Fluid (VOF) surface capturing scheme and a turbulence closure model. This RANS-VOF model is adapted to develop a numerical wind-wave-current …

Water Chemistry Dynamics In Four Vernal Pools In Maine, Usa, Lydia H. Kifner

Electronic Theses and Dissertations

Vernal pools are small seasonal wetlands that are a common landscape feature that contribute to biodiversity in northeastern North American forests. However, even basic information about their biogeochemical functions, such as carbon cycling, is limited. Dissolved gas concentrations (CH₄, CO₂) and other water chemistry parameters were monitored weekly at the bottom and surface of four vernal pools in central and eastern Maine, USA, from April to August 2016. The vernal pools were supersaturated with respect to CH₄ and CO₂ at all sampling dates and locations. Concentrations of dissolved CH₄ and CO₂ ranged …

Structural Behavior Of Inflatable, Reinforced, Braided, Tubular Members, Joshua Clapp

Electronic Theses and Dissertations

The Hypersonic Inflatable Aerodynamic Decelerator (HIAD) system being developed by the National Aeronautics and Space Administration (NASA) is an inflatable structure composed of multiple, concentric, pressurized tori, load straps, and a thermal protection system. The HIAD overcomes limitations inherent with the use of rigid decelerators since the deployed diameter is much larger than the packed size, which makes it an enabling technology for new opportunities in space exploration. The HIAD is designed to decelerate and protect spacecraft during atmospheric re-entry. The objective of this research was to improve understanding of structural behavior of HIAD components through material testing, structural testing …

Window Inserts And The People Adopting Them: Building Sustainable Communities In Maine, Daniel Sean Mistro

Electronic Theses and Dissertations

Residents of Maine face a large monetary expense to heat their homes in the winter. In Maine it takes 540 gallons of heating oil each year to heat a typical home [1]. Interior window inserts may be a practical solution to improve comfort, save money, and consume less environmentally harmful fossil fuels during cold winter months. The window inserts discussed in this paper are custom measured to fit into a window and consist of a wooden frame that is wrapped in two layers of polyolefin film and weather stripped for a snug fit. Commercial inserts cost $20-$36/square foot, or approximately …

Large Payload Hiad Systems: Development Of Computationally Efficient Modeling Strategies And Structural Investigations, Andrew C. Young

Electronic Theses and Dissertations

The hypersonic inflatable aerodynamic decelerator (HIAD) system under development by the National Aeronautics and Space Administration (NASA) has the potential to deliver the size of payloads to the Martian surface that will be necessary for future human-scale missions. An important step in realizing the promise of the HIAD system is to understand the structural behavior of this inflatable, textile, relatively compliant system. This is accomplished through structural testing and the development of structural modeling and analysis methodologies and tools. The structural modeling tools that have been developed to date utilize a continuum, shell-based finite element (FE) analysis approach. This methodology …

Feasibility Of Using 3d Printed Molds For Thermoforming Thermoplastic Composites, Sunil Bhandari

Electronic Theses and Dissertations

This thesis presents a novel combined experimental and numerical mechanics approach for characterizing 3D printed thermoplastic materials by the fused deposition modeling process for thermoforming thermoplastic composites. The implications of this work are:

1. a methodology for model-based performance evaluation of 3D printed structural parts, and
2. an improved design of 3D printed molds for composites manufacturing, which has potential for material innovations and scaled-up applications in additive manufacturing.

The thesis formulates basic criteria for selection of thermoplastic polymer used for the 3D printed mold based on forming temperatures. The thesis creates a lattice and shell finite element model of the 3D …