published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy

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The impingement of supersonic jets on surfaces is of interest because of its important application to jet blast deflectors (JBD), and short takeoff and vertical landing aircraft (STOVL) during hover. Typically, on an aircraft carrier deck, the impingement of the jet blast on the deflector generates impingement tones, and structural vibrations, not only on the JBD but also on the ship deck. Therefore, apart from direct transmission of jet noise to the gallery level, there is a component of noise transmitted due to the impingement of the jet on the JBD. The objectives of this work are to study the pressure spectra (i) on a flat plate, and separately on a cone due to axisymmetric impingement of a supersonic underexpanded cold jet issuing from a convergent-divergent nozzle and (ii) on a plane jet impinging on a finite plate and an adjoining ground plane due to the impingement of a planar jet on the plate. The characteristics of the surface pressure fluctuations are numerically investiga ted using WIND-US 2.0. The time-dependent, compressible Euler equations for perfect gas are employed for the present computations. The impingement distance between the jet nozzle and the deflector plate, and the plate inclination with respect to the incident jet are varied. The impingement zone stagnation bubble and a high-speed radial jet with several embedded structures (shocklets) were identified on the perpendicular plate. Flows involving cones reveal the presence of detached cone shocks, enclosing a recirculation zone. The location and magnitude of the peak pressure on the cone surface are a strong function of the cone apex angle. For the two-dimensional jet impingement on angled plate the peak value of pressure occurs at normal jet impingement. The pressure at the intersection point of the plate and the ground plane is sometimes higher than the peak pressure on the plate. Beyond this point there is a sharp decrease in pressure. As the flow accelerates, an oblique shock is / Beyond this point there is a sharp decrease in pressure. As the flow accelerates, an oblique shock is sometimes formed in this grazing flow region. A recirculation region at the lower lip of the nozzle was observed for all the separation distances and plate inclinations. / by Binu Pundir. / Thesis (Ph.D.)--Florida Atlantic University, 2011. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2011. Mode of access: World Wide Web.

A common technique to improve the performance of shell and tube heat exchangers (STHE) is by redirecting the flow in the shell side with a series of baffles. A key aspect in this technique is to understand the interaction of the fluid dynamics and heat transfer. Computational fluid dynamics simulations and experiments were performed to analysis the 3-dimensional flow and heat transfer on the shell side of an STHE with and without baffles. Although, it was found that there was a small difference in the average exit temperature between the two cases, the heat transfer coefficient was locally enhanced in the baffled case due to flow structures. The flow in the unbaffled case was highly streamed, while for the baffled case the flow was a highly complex flow with vortex structures formed by the tip of the baffles, the tubes, and the interaction of flow with the shell wall. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

Tam Wai Shing = 穩態環流的熱傳送與縱橫比之關係及其與湍流狀態的瑞利-伯纳德對流之聯繫 / 譚偉誠. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (leaves 59-61). / Text in English; abstracts in English and Chinese. / Tam Wai Shing = Wen tai huan liu de re chuan song yu zong heng bi zhi guan xi ji qi yu tuan liu zhuang tai de Ruili-Bonade dui liu zhi lian xi / Tan Weicheng. / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Review of the theoretical studies of heat transport by turbulent convection --- p.5 / Chapter 2.1 --- The marginal stability arguments --- p.7 / Chapter 2.2 --- Chicago mixing zone model --- p.7 / Chapter 2.3 --- Shraiman and Siggia theory --- p.10 / Chapter 2.4 --- Grossmann and Lohse Theory --- p.12 / Chapter 2.4.1 --- Estimation of the kinetic dissipation --- p.13 / Chapter 2.4.2 --- Estimation of the thermal dissipation --- p.14 / Chapter 2.4.3 --- The four regimes --- p.15 / Chapter 3 --- Aspect-ratio dependence: The problem studied --- p.19 / Chapter 3.1 --- The velocity field --- p.21 / Chapter 3.1.1 --- Incompressible flow --- p.21 / Chapter 3.1.2 --- Large-scale circulating flow --- p.21 / Chapter 3.1.3 --- No-slip boundary conditions --- p.22 / Chapter 3.2 --- The functions f(x) and g(y) --- p.23 / Chapter 3.3 --- Boundary conditions for the temperature field --- p.23 / Chapter 3.4 --- Important parameters in the numerical calculation --- p.24 / Chapter 4 --- The numerical calculations --- p.31 / Chapter 5 --- Results and discussions --- p.34 / Chapter 5.1 --- Nu-Г Relationship --- p.38 / Chapter 5.2 --- Nu - Pe Relationship --- p.41 / Chapter 6 --- Implications for heat transport by Rayleigh-Benard convection --- p.49 / Chapter 6.1 --- Nu-Ra relationship --- p.50 / Chapter 6.2 --- Comparison with recent experimental results --- p.52 / Chapter 7 --- Conclusions --- p.57 / Bibliography --- p.59

Orientador: Eduardo Carlos Bianchi / Co-orientador: Vicente Luiz Scalon / Banca: Dayse Iara dos Santos / Banca: Bento Rodrigues de Pontes Junior / Banca: Olivio Novaski / Banca: Jaime Gilberto Duduch / O Programa de pós Graduação em Ciência e Tecnologia de Materiais, PosMat, tem caráter institucional e integra as atividades de pesquisa em materiais de diversos campi / Resumo: A retificação é um processo de acabamento, sendo normalmente o último processo da sequência de fabricação. Assim, qualquer benefício obtido na retificação é de grande valor para todo o processo de fabricação. Danos térmicos são uma das principais limitações do processo de retificação, por isso, é importante compreender os fatores que afetam a temperatura de retificação. o desempenho da técnica de lubri-refrigeração otimizada foi investigada e comparada com a técnica de lubri-refrigeração convencional para estimar o fluxo do calor dissipado para a peça de trabalho e assim verificar o máximo aumento da temperatura superficial da zona de contato entre o rebolo convencional de Al2O3 e a peça de aço ABNT 1020, levando-se em conta variáveis tais como a distribuição total de fluxo de calor e como ele é modelado (retangular ou triangular), as características térmicas da peça de trabalho e assim por diante. O problema direto foi solucionado a partir da equação de difusão de calor associado ao problema de condução de calor bidimensional em regime transiente utilizando-se do Método de Volumes Finitos para a sua discretização. Para a solução do problema inverso em transferência de calor fez-se o uso das temperaturas medidas experimentalmente para estimar o fluxo de calor na interface entre o rebolo e a superfície da peça (função objetivo). Foi aplicada a técnica inversa da Seção Áurea para a estimativa do fluxo de calor. Quando comparada à técnica do método convencional de aplicação de fluido, o fluxo de calor conduzido para a peça de trabalho foi reduzido em 84,0% nos ensaios realizados com profundidade de corte de 30um, em 74% nos ensaios com 45um e em 62,2% nos ensaios mais severos de 60um, demonstrando de forma clara e aplicabilidade do método otimizado de aplicação de fluido. O método otimizado foi efetivo na redução das temperaturas superficiais das regiões afastadas da região... / Abstract: Grinding is a finishing process, usually being the last sequence of the manufacturing process. Thus, any benefit obtained in the grinding is of great value to the entire manufacturing process. Thermal damage is one of the main limitations of the grinding process, so it is important to understand the factors that affect the temperature rectification. The technial performance of optimized lubrification and cooling was investigated and compared with the conventional lubrification and cooling technique to estimate the flow of heat dissipated into the workpiece and thus to check the increase in the maximum surface temperature in the contact zone between the conventional grinding wheel Al2O3 and the piece of AISI 1020, taking into account variables such as the total distribution of heat flow and how it is modeled (rectangular or triangular), the thermal characteristics of the workpiece, the geometry of the grinding wheel/workpiece interface and so on. The direct problem was solved from the heat diffusion equation associated with the problem of two-dimensional heat conduction in transient regime utilizing the finite volume method for its discretization. For the solution of the inverse problem of theat transfer the experimentally measured temperatures was used to estimate the heat flux at the interface between the grinding wheel and workpiece surface (objective function). The inverse technique of Golden Section was applied to estimate heat flow. When compared to the conventional technique of method of application fluid, the heat flow conducted to the workpiece was reduced by 84,0% in the tests performed with cutting depth of 30um, at 74,0%in the tests with 45 um and 62,2% in the tests practices of 60 um, clearly demonstrating the applicability of the optimized method of fluid application. The optimized method was effective in reducing the surface temperature of the remotest regions in the cutting region indicating that the front and back cooling... / Doutor

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / by Alfred Walters Reed. / Ph.D.

Thesis. 1975. Ph.D.--Massachusetts Institute of Technology. Dept. of Mechanical Engineering. / Vita. / Bibliography: leaves 76-78. / Ph.D.

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

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND AERONAUTICS. / Vita. / Includes bibliographical references. / Ph.D.