Engineering Commons^™

Multi Rotor Wind Turbine Design And Cost Scaling, Preeti Verma

Masters Theses 1911 - February 2014

The current generation wind turbines are upscaled into multi megawatt range in terms of output power. However, the energy benefit from the turbine is offset by the increased mass and cost. Twenty MW wind turbines are now feasible with rotor diameters up to 200 m, according to a new report from the EU-funded UpWind project in 2011. The question is, how much bigger can wind turbines get realistically? One concept worth considering, and the one that is the subject of this thesis, is to have more than one rotor on a single support structure. Such turbines could have a greater …

The Effect Of Leaves And Steel Support Cables On The Dynamic Properties Of Northern Red Oak (Quercus Rubra) With Co-Dominant Trunks, Mark Reiland

Masters Theses 1911 - February 2014

Natural frequency and damping ratio were measured for ten forest grown northern red oak trees with co-dominant trunks. Steels support cables were installed in the canopies of five of the sample trees prior to measurement. Free vibration testing was performed during periods when leaves were and were not present. An accelerometer mounted at the base of the co-dominant union measured the acceleration time history during the free vibration testing. Natural frequency was determined from the acceleration time history using power spectral density analysis. Damping ratios were calculated from the power spectral density plots using the half power bandwidth method.

Trees …

Techniques For Industrial Implementation Of Emerging Semantic Technologies, Jay T. Breindel

Masters Theses 1911 - February 2014

Techniques for the industrial implementation of emerging semantic technologies are presented in this research. Every new design, project, and procedure within a company generates a considerable amount of new information and important knowledge. Furthermore, a tremendous amount of legacy knowledge already exists within companies in electronic and non-electronic formats. All of this generated knowledge results in the need for tools and techniques to represent, structure, and reuse this knowledge. Researchers have spent considerable time and effort developing semantic knowledge management systems, with anticipation that these tools will address these knowledge management needs. However, little has been done to implement these …

Simulations Of Non-Contact Creep In Regimes Of Mixed Dominance, Maija Benitz

Masters Theses 1911 - February 2014

Improvement of high temperature applications relies on the further development of ultra-high temperature materials (UHTMs). Higher performance and efficiency is driving the need for improvements in energy conversion and propulsion systems. Rocket nozzles, gas turbine engines and hypersonic aircraft depend on a better understanding of a material's performance at high temperatures. More specifically, the characterization of creep properties of high temperature materials is required. Conventional creep testing methods are limited to about 1700 degrees Celsius. Non-contact methods have been developed, which rotate spherical samples up to 33,000 rotations per second. A load is supplied by centripetal acceleration causing deformation of …

Viscoelastic Flow Through Contraction Geometries, Ashwin Karthik Sankaran

Masters Theses 1911 - February 2014

Contraction flow of viscoelastic fluids has been a benchmark problem in non-Newtonian fluid mechanics because it mimics flows occurring in a number of industrial applications. It is also of considerable interest to academia to gain fundamental understanding of factors that affect the evolution of vortices and a complete understanding of the dynamics for a simple polymeric fluid has not been achieved. In this two part study we investigate the effect of pre deformation of a Boger fluid in a contraction geometry and the flow of surfactants in a parallel contraction geometry.

Entry flow of a polymeric fluid results in the …

Vibration Reduction Of Offshore Wind Turbines Using Tuned Liquid Column Dampers, Colin Roderick

Masters Theses 1911 - February 2014

Offshore wind turbines (OWTs) are becoming an accepted method for generating electricity. The environmental conditions of offshore locations often impose high wind and wave forces on OWTs making them susceptible to intense loading and undesirable vibrations. One method to reduce system vibrations is through the use of structural control devices typically utilized in civil structures. Tuned liquid column dampers (TLCDs) show great promise in the application to OWTs due to their high performance and low cost. This thesis examines the use of TLCDs in OWTs.

Equations of motion for limited degree-of-freedom TLCD-turbine models are presented. A baseline analysis of each …

A Nonlinear Model For Wind-Induced Oscillations Of Trees, Lakshmi Narayanan Ramanujam

Masters Theses 1911 - February 2014

Ambient wind causes trees to oscillate. Wind-induced oscillations of trees constitute a fluid-structure interaction problem, which has been studied by many researchers from various points of view. However, there is yet a lot to be done. From an engineering point of view, the complex structure of trees, which are very different from man-made structures, as well as the highly nonlinear interaction between wind and tree, makes it a challenging task to predict the amplitude and frequency of the resulting oscillations. From a biological point of view, the influence of wind on photosynthesis as well as the growth and death of …

Physical Model Of The Feeding Strike Of The Mantis Shrimp, Suzanne M. Cox

Masters Theses 1911 - February 2014

A physical model was built to study the properties of the feeding strike of the mantis shrimp that are responsible for drag reduction and cavitation control. The model had three goals: 1) The model was to be outfitted with a method to collect kinematic, force and cavitation data. 2) The velocity and acceleration profile of the model were to be predicted with a mathematical model of the mechanism. 3) The model was to match as many drag and cavitation sensitive properties of the mantis shrimp strike as feasible and have a means to control the rest. The first iteration of …

Investigation Of 3-D Heat Transfer Effects In Fenestration Products, Sneh Kumar

Masters Theses 1911 - February 2014

Buildings in USA consume close to 40% of overall energy used and fenestration products (e.g. windows, doors, glazed-wall etc.) are the largest components of energy loss from buildings. Accurate evaluation of thermal performances of fenestration systems is critical in predicting the overall building energy use, and improving the product performance. Typically, two-dimensional (2-D) heat transfer analysis is used to evaluate their thermal performance as the 3-D analysis is highly complex process requiring significantly more time, effort, and cost compared to 2-D analysis. Another method of evaluation e.g. physical test in a hotbox is not possible for each product as they …

Drag Reduction In Turbulent Flows Over Micropatterned Superhydrophobic Surfaces, Robert J. Daniello

Masters Theses 1911 - February 2014

Periodic, micropatterned superhydrophobic surfaces, previously noted for their ability to provide drag reduction in the laminar flow regime, have been demonstrated capable of reducing drag in the turbulent flow regime as well. Superhydrophobic surfaces contain micro or nanoscale hydrophobic features which can support a shear-free air-water interface between peaks in the surface topology. Particle image velocimetry and pressure drop measurements were used to observe significant slip velocities, shear stress, and pressure drop reductions corresponding to skin friction drag reductions approaching 50%. At a given Reynolds number, drag reduction was found to increase with increasing feature size and spacing, as in …