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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Hypersonic Stationary Crossflow Waves: Receptivity to Roughness

Varun Viswanathan (8032571) 04 December 2019 (has links)
<div>Experiments were performed on a sharp-nosed 7° half-angle cone at a 6° angle of attack in the Boeing/AFOSR Mach-6 Quiet Tunnel (BAM6QT) to study the stationary crossflow instability and its receptivity to small surface roughness. Heat transfer measurements were obtained using temperature sensitive paint (TSP) and Schmidt Boelter (SB) heat transfer gauges. Great care was taken to obtain repeatable, quantitative measurements from TSP.</div><div></div><div>Consecutive runs were performed at a 0° angle of attack, and the heat transfer measured by the SB was found to drop as the initial model temperature increased, while other initial conditions such as stagnation pressure were held constant. This agreed with calculations done using a similarity solution. It was found that repeatable measurements at a 6° angle of attack could be made if the initial model temperature was controlled and the patch location that was used to calibrate the TSP was picked in a reasonable and consistent manner.</div><div></div><div>The Rod Insertion Method (RIM) roughness, which was used to excite the stationary crossflow instability, was found to be responsible for the appearance of the streaks that were analyzed. The signal-to-noise ratio in the TSP was too low to properly measure the streaks directly downstream of the roughness insert. The heat transfer along the streak experienced linear growth, peaked, and then slightly decayed. It is possible this peak was saturation. The general trend was that the growth of the streaks moved farther upstream as the roughness element height increased, which agreed with past computations and low speed experiments. The growth of the streak also moved farther upstream as the freestream Reynolds number increased. The amplitude of the streaks was calculated by non-dimensionalizing the heat transfer using the laminar theoretical mean-flow solution for a 7° half-angle cone at a 6° angle of attack. The relationship between the amplitude and the non-dimensional roughness height was approximately linear in the growth region of the streaks.</div>
2

Sobre seÃÃes cÃnicas / On conic sections

Josà Adriano dos Santos Oliveira 18 June 2015 (has links)
CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / O estudo realizado nesta dissertaÃÃo, busca apresentar as seccÃes cÃnicas, dando Ãnfase a uma abordagem por meio de uma geometria sintÃtica e elementar, onde o trabalho à desenvolvido da seguinte forma: inicia-se com uma abordagem histÃrica, assim como a sua relaÃÃo com o cone circular; em seguida, à feito um estudo sintÃtico sobre as cÃnicas, exclusivamente, no plano; apresenta-se algumas superfÃcies quÃdricas; a equaÃÃo geral do segundo grau à apresentada como uma representaÃÃo algÃbrica de uma cÃnica e sÃo mostradas diversas situaÃÃes, onde as cÃnicas surgem de forma, curiosamente, natural, alÃm das inÃmeras aplicaÃÃes prÃticas em diversas Ãreas do conhecimento. / The study in this dissertation, seeks to present the conic sections, emphasizing an approach by means of a synthetic and elementary geometry, where the work is carried out as follows: begins with a historical approach, as well as their relationship with the circular cone; then itâs done a synthetic study on the conical exclusively on the plan; It presents some quadric surfaces; the general equation of the second degree is presented as an algebraic representation of a conic and are shown several situations where the conical arise so, curiously, natural, in addition to numerous practical applications in various fields of knowledge.

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