Pratt Fellow Projects

Listed below are the proposed projects for the Fall 2017 Pratt Fellows Application cycle. Interested students are strongly encouraged to contact Professor Bliss to discuss these opportunities. 

For information regarding the Pratt Fellows Program please visit http://pratt.duke.edu/undergrad/students/research-fellows

Project: Acoustic Loudspeaker Design Capable of Producing Controllable Directivity Patterns for Sound Field Analysis and Sound Reproduction 

There is a need for a loudspeaker design that can produce sound fields with prescribed directivity patterns over a broad frequency range.  The term directivity refers to the spatial distribution of radiated acoustic intensity.  In normal loudspeaker design the directivity varies as a function of frequency.  The goal for this project is to have the same prescribed directivity pattern over a wide frequency range.  The design is envisioned as a multi-element array, namely many small high-quality speakers mounted in an enclosure (likely spherical or cylindrical) fabricated with a 3-D printer.  An accurate and versatile sound source of this type can be used as a reference source to study the effect of directivity on sound fields in vehicles, in both civilian and military applications. Another possible use is high fidelity sound reproduction in studios, performance spaces, and homes.  There is considerable interest in the relative merits of sound reproduction using sources with directivity independent of frequency.  The project involves analytical and computational modeling, design and construction, and testing in the anechoic chamber.  The student will work directly with the faculty advisor and his team on an individually tailored project.  The student will become knowledgeable in acoustics and loudspeaker design, and will significantly improve their analysis and experimental skills.  Open to one or two students.

Project: Novel Wind Turbine Designs to Improve Efficiency and Allow Higher Turbine Density in Wind Farms

Wind turbines are often sited in groups called wind farms to extract energy in windy areas on land or at sea.  Wind turbine wakes contain less energetic flow due to the extraction of power.  Downstream turbines operating in or near those wakes are substantially less efficient due to this wake shielding effect, requiring turbines to be spaced far apart, causing wind farms occupy large amounts of space.  The overall wind farm efficiency can be increased by novel design changes to steer the wakes away from turbines immediately downstream, and overall to cause the wakes to convect upward.  If the turbine wake can be made to ascend, the less-energetic fluid it carries rises above the downwind turbines, and is replaced by a downward flow of more energetic fluid from higher up.  If employed throughout a wind farm, there would be a net aerodynamic pumping that directs energetic higher altitude wind into the downstream turbines.  The project will develop aerodynamic models for novel wind turbine designs, including axis tipping and hybrid counter-rotating designs, and assess the potential increase in efficiency of wind farms.  Analysis, computation, experimental turbine design and wind tunnel testing will be components of the project.  The student will work directly with the faculty advisor and his team on an individually tailored project. The student will become knowledgeable in wind turbine aerodynamics and vortex flows, and will significantly improve their analysis and experimental skills.  Open to one or two students.

Project: Innovative Structures for Noise and Vibration Reduction of Flight and Ground Vehicles

Modern flight and ground vehicles face demanding technical challenges in the area of noise and vibration reduction.  Lightweight structures improve performance and efficiency, but it is difficult to reduce noise and vibration because the structures are more flexible.  It is necessary to attenuate sound and vibration through walls, floors, frames, and trim panels on vehicles, and to shield payloads on rocket nose cones.  Noise sources include engine and propulsion noise, aerodynamic noise, and road noise.  The research involves the development of a new approach by the invention of lightweight, flexible structures that inherently resist the transmission of sound and vibration. Multi-Element/Multi-Path (MEMP) structures divide a structure into a number of constituent layered subsystems with separate, but coupled, wave transmission paths.  The concept utilizes the inherent dynamics of the system, rather than damping, to achieve noise and vibration reduction over a wide frequency range.  The project will have experimental, analytical, and computational aspects.  The student will work directly with the faculty advisor and his team on an individually tailored project. The student will become knowledgeable in acoustics and vibration, and will significantly improve their analysis and experimental skills.  Open to one or two students.