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The interaction of a rectangular turbulent jet with a free surface for three jet-exit aspect ratios is experimentally investigated using Particle Image Velocimetry (PIV). The jet exits from a sharp edged rectangular orifice plate, parallel to the free surface and has a jet width of d = 10 mm. Aspect ratios of 1, 2 and 4 are studied with a fixed offset of 3d from the free surface. Reynolds and Froude numbers based on the bulk velocity are 6900 and 1.27 respectively. Detailed 2-D velocity fields are captured using the PIV in the central x-y plane for 0 < x/d < 23.5. The distribution of Reynolds shear stresses and turbulent kinetic energy show that they are suppressed in the vicinity of the free surface due to confinement. There was a significant effect of nozzle geometry on the reattachment point and recirculation region of the jets. / May 2016

published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy

As optical interconnects make their paces to replace traditional electrical interconnects, implementing low cost optical components and hybrid optic-electronic systems are of great interest. In the research work described in this dissertation, we are making our efforts to develop several practical optical components using novel printing technologies including imprinting, ink-jet printing and a combination of both. Imprinting process using low cost electroplating mold is investigated and applied to the waveguide molding process, and it greatly reduces the surface roughness and thus the optical propagation loss. The imprinting process can be applied to photonic components from multi-mode waveguides with 50[mu]m critical dimension down to photonic crystal structures with 500nm hole diameter. Compared to traditional lithography process, imprinting process is featured by its great repeatability and high yield to define patterns on existing layers. Furthermore we still need an approach to deposit layers and that is the reason we integrate the ink-jet printing technology, another low-cost, low material consumption, environmental friendly process. Ink-jet printing process is capable of depositing a wide range of materials, including conductive layer, dielectric layer or other functional layers with defined patterns. Together with molding technology, we demonstrate three applications: proximity coupler, thermo-optic (TO) switch and electro-optic (EO) polymer modulator. The proximity coupler uses imprinted 50[mu]m waveguide with embedded mirrors and ink-jet printed micro-lenses to improve the board-to-board optical interconnects quality. The TO switch and EO modulator both utilize imprinting technology to define a core pattern in the cladding layer. Ink-jet printing is used to deposit the core layer for TO switch and the electrode layers for EO modulator. The fabricated TO switch operates at 1 kHz with less than 0.5ms switching time and the EO modulator shows V[pi][middle dot]L=5.68V[middle dot]cm. To the best of our knowledge, these are the first demonstrations of functional optical switches and modulators using printing method. To further enable the high rate fabrication of ink-jet printed photonic and electronic devices with multiple layers on flexible substrate, we develop a roll-to-roll ink-jet printing system, from hardware integration to software implementation. Machine vision aided real time automatic registration is achieved when printing multiple layers. / text

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This research evaluates the Joint Strike Fighter (JSF) Program acquisition of Pratt & Whitney (P and W) F135 and the General Electric Aircraft Engines/Rolls Royce (GEAE/RR) F136 engines. This study examines existing research on the first *Great Engine War*. The first Great Engine War was an attempt by the Government to encourage Pratt & Whitney, the sole winner of the F- 16 fighter engine propulsion contract, to be more responsive to shortcomings in design and support. When P and W declared that any design changes would be out of the scope of the current contract, the government contracted with GEAE to produce an alternate engine design to compete against P&W. The competition was a success. The study also includes Interviews with veterans of the Great Engine War. The findings are balanced against the current JSF acquisition planning to ensure applicability. The research and analysis yielded the following recommendations to guide the JSF future engine acquisition: ensure airframe commonality for both engines, continue to purchase and support the engines as Government-Furnished Equipment (GFE), utilize supportability costs as competition criteria, maintain a concerted effort to encourage both competitors to attempt to win the maximum share, and do not participate in a Component Improvement Program.