Fluid flows past single and multiple cylinders in different configurations are investigated both experimentally and numerically. Three and five in-line cylinders and in-line and staggered bundles of cylinders with different pitch-to-diameter ratios are considered. Experimental work comprises of laser-Doppler velocimetry and flow visualization obtained in a water tunnel and skin friction, pressure, lift, drag and hot-wire measurements obtained in a wind tunnel. Both steady and pulsed flows are considered. Numerical work consists of finite element analysis of Navier-Stokes and energy equations governing viscous fluid flow past single and multiple cylinders. Detailed measurements of the fluid dynamic quantities for flow past cylinders reveal that flow pulsation at frequencies which induce lock-on increases the organization of the flow in gaps between cylinders. A new pattern of flow field is found for flow past a triad and a pentad of cylinders with a pitch-to-diameter ratio of l.8. The numerical analysis generates important integral characteristics like flow resistance and heat transfer. A staggered square arrangement of finite bundle of cylinders is found to have better heat transfer characteristics compared to the in-line or staggered equilateral-triangular arrangements. / Ph. D. / incomplete_metadata

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Master of Science / Department of Mechanical and Nuclear Engineering / B. Terry Beck / Mohammad H. Hosni / Cavitation is the change of a liquid to a two-phase mixture of liquid and vapor, similar to boiling. However, boiling generates a vapor by increasing the liquid temperature while cavitation generates vapor through a decrease in pressure. Both processes are endothermic, removing heat from the surroundings. Both the phase change and heat absorption associated with cavitation provide many engineering applications, including contributing to a new type of refrigeration cycle under development. Cavitation can occur at or below the vapor pressure; conditions that delay cavitation and allow for a metastable liquid are not well understood. A converging-diverging nozzle was designed and fabricated to create a low pressure region at the nozzle throat. The converging section of the nozzle increased the water velocity and decreased the pressure, according to Bernoulli’s principle. A cavitation front was formed slightly past the nozzle throat. The cavitation location suggested that the water was metastable near the nozzle throat. Flow through the system was controlled by changing the nozzle inlet and outlet pressures. The flowrate of water was measured while the outlet pressure was lowered. The flowrate increased as the outlet pressure dropped until cavitation occurred. Once cavitation initiated, the flow became choked and remained constant and independent of the nozzle outlet pressure. High-speed imagery was used to visualize the flow throughout the nozzle and the formation and collapse of cavitation in the nozzle’s diverging section. High-speed video taken from 1,000 to 35,000 frames per second captured the formation of the cavitation front and revealed regions of recirculating flow near the nozzle wall in the diverging section. Particle Image Velocimetry (PIV) was used to measure the velocity vector field throughout the nozzle to characterize flow patterns within the nozzle. PIV showed that the velocity profile in the converging section and throat region were nearly uniform at each axial position in the nozzle. In the diverging section, PIV showed a transient, high-velocity central jet surrounded by large areas of recirculation and eddy formation. The single-phase experimental results, prior to cavitation onset, were supplemented by Computational Fluid Dynamics (CFD) simulations of the velocity distribution using Fluent software.

Approved for public release, distribution is unlimited / The geometric characteristics of flapping-wing propulsion are studied experimentally through the use of a force balance and a Micro Air Vehicle (MAV) system. The system used is built to duplicate the propulsion system currently on the flying model of the Naval Postgraduate School (NPS) MAV model. Experiments are carried out in a low speed wind tunnel to determine the effects of mean separation and plunge amplitude on the flapping wing propulsion system. Additionally, the effects of flapping-wing shape, flapping frequency, and MAV angle of attack (AOA) are also investigated. Some flow visualization is also performed. The intent is to optimize the system so that payload and controllability improvements can be made to the NPS MAV. / Ensign, United States Naval Reserve

The goal of this project is to use inspiration acquired from bird flight to optimize the wing planform of micro-air vehicle wings. Micro-air vehicles are used by the military for surveillance and for search and rescue missions by civilian first-responders. These vehicles fly in the same low Reynolds number regime as birds, and have low aspect ratios similar to the pheasants and grouse of the order Galliformes. Conventional analysis is difficult for low Reynolds numbers, prompting use of biologically inspired methods of optimization. Genetic algorithms, which mimic the process of evolution in nature, were used to define wing shapes that were tested in wind tunnel experiments. In these experiments, lift-drag ratios at various angles of attack were measured on scale model micro-air vehicle wings (with variable length feathers) similar in shape to a bird wing. The planform shape of the scale model wing evolved in the wind tunnel flow over successive generations to ultimately produce superior wings with higher lift-drag ratios. The low angle of attack wings were easily optimized into a wing shape different from and potentially more efficient than the oft-used Zimmerman planform. The process was repeated for a higher angle of attack, near stall conditions, which yielded a different wing planform shape. Chord distributions of the optimized low angle of attack wings were found to closely match the same distributions of birds from the order Galliformes. Results from flow visualization studies meant to illuminate possible physics responsible for the higher lift-drag ratios were also investigated.

Futebol é um esporte fascinante que capta a atenção de milhões de pessoas no mundo. Equipes de futebol profissionais, bem como os meios de comunicação, têm um profundo interesse na análise de partidas de futebol. Análise estatística é a abordagem mais usada para descrever um jogo de futebol, no entanto, muitas vezes eles não conseguem captar a evolução do jogo e as mudanças de estratégias que aconteceram. Neste trabalho, apresentamos Visual Soccer Match Analysis (VSMA), uma ferramenta para a compreensão dos diferentes aspectos relacionados com a evolução de um jogo de futebol. A nossa ferramenta recebe como entrada as coordenadas de cada jogador durante o jogo, bem como os eventos associados. Apresentamos um design visual que permite identificar rapidamente padrões relevantes em jogo. A abordagem foi desenvolvida em conjunto com colegas da área da educação física com experiência em análise de futebol. Validamos a utilidade da nossa abordagem utilizando dados de várias partidas, juntamente com avaliações de especialistas. / Soccer is a fascinating sport that captures the attention of millions of people in the world. Professional soccer teams, as well as the broadcasting media, have a deep interest in the analysis of soccer matches. Statistical summaries are the most-used approach to describe a soccer match. However, they often fail to capture the evolution of the game and changes of strategies that happen. In this work, we present the Visual Soccer Match Analysis (VSMA) system, a tool for understanding the different aspects associated with the evolution of a soccer match. Our tool receives as input the coordinates of each player throughout the match and related events. We present a visual design that allows to quickly identify relevant patterns in the match. Our approach was developed in conjunction with colleagues from the physical education field with expertise in soccer analysis. We validated the system utility using several matches together with expert evaluations.

Thesis. 1979. Ph.D.--Massachusetts Institute of Technology. Dept. of Mechanical Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND AERO / Includes bibliographical references. / by Wen Liu. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / by Francesca De Siervi. / M.S.

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