Recent MSCE Theses

Dynamic Response Assessment and Modeling of a Small Wind Turbine Structure
Molly Pruess, MSCE May 2013     
Advisor: Dr. Damon Fick
Committee Members: Dr. Sangchul Bang, Dr. Lidvin Kjerengtroen

Abstract: Demand for energy is continually increasing worldwide and new sources of energy must be tapped. Small wind turbine (SWT) energy production output will have an important role in the energy future of rural homes and farming operations. SWTs are often located on sites with less than ideal wind conditions, resulting in more turbulent wind loading and a larger dynamic input. A better understanding of the dynamic frequencies of small wind turbines could lead to more efficient structural and foundation designs. By analyzing raw dynamic measurements from three types of measurement transducers (pressure cells, tiltmeters, and strain gages) using a fast Fourier transform, the natural frequencies of vibrations of an 80 ft. SWT were found and compared to three analytical, linear elastic, finite element models. From the data collected, it was concluded that using the upper bound of subgrade modulus design recommendations for spring constant calculations over estimated the first and second measured modal frequencies by approximately 1.5%. Using the lower bound design recommendations underestimated the same measured frequencies by approximately 9%. Verifying the structural design using dynamic analysis is achievable if the structural geometry and a reasonable range of engineering soil properties for the soil type are well understood.

Evaluating Temporal and Spatial Scale Issues with Hydrologic Models
Dol Raj Chalise, MSCE Fall 2013
Advisor: Dr. Thomas Fontaine
Committee Members: Dr. Scott Kenner, Dr. Adel Haj

Abstract: The relative accuracy of rainfall runoff models is an important issue. Some models may perform better than others in specific scenarios (e.g. wet vs. dry climates; forested vs. agricultural land use; long vs. short time steps for simulation). Two widely used models were selected for comparison to simulate runoff for watersheds in the Black Hills of South Dakota. The two models, the Precipitation Runoff Modeling System (PRMS) and Hydrological Simulation Program Fortran (HSPF), are both semi distributed, deterministic hydrological tools that simulate the impacts of precipitation, land use and climate on basin hydrology and streamflow. PRMS is primarily used by the U.S. Geological Survey (USGS) to simulate basin hydrology across the United States. HSPF is used by a larger base of public and government modelers to simulate basin hydrology, sediment processes, and water quality worldwide. One of the primary applications of this research is to help potential users to select the more appropriate hydrologic model, HSPF or PRMS, when working with a specific size of watershed. Results indicate that the HSPF better estimated annual, monthly, and daily water budget than the PRMS for a small watershed. The HSPF better estimated annual water budget than the PRMS for a large watershed. The PRMS betters estimated monthly and daily water budget than the HSPF for a large watershed when wet and dry periods were calibrated individually. The results indicate that the temporal and spatial scale variability influences the accuracy of HSPF and PRMS model simulations. The study suggests that an appropriate selection of a model for specific size of a watershed should be based on a specific hydrologic question that a user is seeking to answer.