Thesis (M.S.)--Brigham Young University. Dept. of Mechanical Engineering, 2006. / Includes bibliographical references (p. 37-38).

Thesis (PhD) - Swinburne University of Technology, School of Engineering and Science, 2009. / A thesis submitted in accordance with the regulations for the degree of Doctor of Philosophy, School of Engineering and Science, Swinburne University of Technology, 2009. Typescript. Includes bibliographical references (p. 315-330)

An experiment was conducted to investigate the aerodynamic losses of two high-pressure steam turbine nozzles (526A, 525B) subjected to a large range of incident angle and exit Mach number. The blades were tested in a 2D transonic windtunnel. The exit Mach number ranged from 0.60 to 1.15 and the incidence was varied from -34o to 35o. Measurements included downstream Pitot probe traverses, upstream total pressure, and endwall static pressures. Flow visualization techniques such as shadowgraph photography and color oil flow visualization were performed to complement the measured data. When the exit Mach number for both nozzles increased from 0.9 to 1.1, the total pressure loss coefficient increased by a factor of 7 as compared to the total pressure losses observed at subsonic condition (M2<0.9). For the range of incidence tested, the effect of flow incidence on the total pressure losses is less pronounced. Based on shadowgraphs taken during the experiment, it's believed that the large increase in losses at transonic conditions is due to strong shock/boundary layer interaction that may lead to flow separation on the blade suction surface. From the measured total pressure coefficients, a modified loss model that accounts for higher losses at transonic conditions was developed. The new model matches the data much better than the existing Kacker-Okapuu model for transonic exit conditions. / Master of Science

The study of designing stable aircraft has been widespread and ongoing since the early days of Orville and Wilbur Wright and their famous Wright Flyer airplane. All aircraft as they fly through the air are subject to minor changes in the forces acting on them. The field of aircraft stability seeks to understand and predict how aircraft will respond to these changes in forces and to design aircraft such that when these forces change the aircraft remains stable. The mathematical equations used to predict aircraft stability rely on knowledge of the location of the aerodynamic center, the point through which aerodynamic forces act on an aircraft. The aerodynamic center of an aircraft is a function of the aerodynamic centers of each individual wing, and the aerodynamic center of each wing is a function of the aerodynamic centers of the individual airfoils from which the wing is made. The ability to more accurately predict the location of the airfoil aerodynamic center corresponds directly to an increase in the accuracy of aircraft stability calculations. The Aerolab at Utah State University has develop new analytic mathematical expressions to describe the location of the airfoil aerodynamic center. These new expressions do not suffer from any of the restrictions, or approximations found in traditional methods, and therefore result in more accurate predictions of airfoil aerodynamic centers and by extension, more accurate aircraft stability predictions.

The importance of sports engineering has increased in the past decade as the demand for athletes and their equipment has increased. Similarly, the aerodynamics of blunt bodies such as prolate spheroids is of particular interest to aerodynamicists seeking to reduce drag. A system was developed to measure aerodynamic forces on rugby balls. The rugby balls, which varied in size and surface textures, were tested at multiple angles of attack, rotational rates, and wind tunnel velocities. A force balance utilizing load cells in conjunction with a subsonic wind tunnel was used to obtain lift and drag forces. A detailed description of the complete test apparatus is given including methods of mounting, rotation, calibration and tare measurements. Several methods of data acquisition were investigated and the final method is outlined. The results for two balls are given along with the variation in data from repeated testing. Both the force data trends and a few interesting phenomena are discussed.

A technique for digitally generating random time histories having arbitrarily shaped power spectra is presented. Four random time histories having significantly different statistical and power spectral properties have been generated and analyzed to determine their mean and amplitude distributions. It was found that the distribution of means could be approximated by a normal distribution and that the distribution of amplitudes could be approximated by the sum of a Rayleigh distribution and a normal distribution. An attempt was made to relate the coefficients of the equations used to represent the distributions of means and amplitudes to the power spectral properties of the generated time histories. It was found that two of the coefficients could be related to the power spectral properties of the time histories. The remaining two coefficients were empirically determined since no apparent relationship was found between these coefficients and the power spectral properties of the generated random time histories. In addition a discussion of the applicability of results for estimating fatigue life under randomly varying loads or stresses is presented. / Master of Science

The present thesis project consisted of two parts. First, a general method for determining the transient skin temperatures of bodies during high-speed flight was developed. The governing differential equation was presented for this purpose, giving the fundamental relations between the transient skin temperature and flight history. The determination of all pertinent parameters in the equation was discussed, and the Runge-Kutta numerical method of integration was used to obtain the solution. The method was employed to compute the time history of the skin temperatures for several hypothetical flight plans, and the results presented in the form of graphs. For the Mach number and altitude range investigated, the maximum skin temperature obtained was approximately 2200 °R and was found to be largely independent of the type of trajectory. The second portion of the project consisted of determining the effect of heat insulation on the cooling requirements of the internal structure of a high-speed vehicle. The governing equation for heat conduction through an isotropic solid was developed, and then modified to account for nonhomogeneous materials. The initial and boundary conditions for the governing equation were specified, and the equation solved by the method of finite-differences. The temperatures obtained, the first portion the thesis, were used as the outer surface temperature variation of the insulation, and the time history of the inner surface temperature of the insulation (for several thicknesses) was calculated. To make the problem as general as possible, the results were presented in terms of the thermal diffusivity of the insulating material. For illustrative purposes, an example problem was worked using rock wool as the insulating material. It was found that, by using one-half inch of this insulating material, the maximum temperature obtained by the internal structure was less that 5 percent of the skin temperature. Thus, it was concluded that the increase of the temperature of the internal structure of a high-speed vehicle during a limited time of flight, can be held to structurally permissable values by the use of heat insulation placed between the skin and the internal structure of the vehicle. / Master of Science

Os silos metálicos cilíndricos de chapa corrugada e cobertura cônica são as unidades mais utilizadas no Brasil para o armazenamento de produtos granulares. As principais ações variáveis que atuam sobre os silos são as pressões devidas aos produtos armazenados e ao vento, sendo esta ação crítica quando o silo se encontra vazio. Devido à grande eficiência estrutural da forma cilíndrica e à resistência elevada do aço, estas estruturas são leves e delgadas e, portanto, suscetíveis a perdas de estabilidade local e global e arrancamento. Com a finalidade de avaliar estes efeitos foram realizados estudos teóricos e experimentais sobre as ações do vento em silos. O trabalho foi desenvolvido com ensaios de modelos aerodinâmicos e aeroelásticos em um túnel de vento na Universidade de Cranfield, Inglaterra, com o objetivo de determinar os coeficientes aerodinâmicos no costado e na cobertura. Os resultados mostram que os valores dos coeficientes recomendados pela Norma Brasileira de vento, NBR 6123 (1990), são adequados para o costado. Para a cobertura cônica, como não são especificados pela NBR, são recomendados valores dos coeficientes aerodinâmicos determinados nos ensaios. Conclui-se também que a colocação externa das colunas é a favor da segurança e que o uso de anéis enrijecedores no costado é indicado e muito importante para a estabilidade local e global da estrutura do silo. / The steel cylindrical silos made of corrugated sheets with conical roofs are the most used units to the storage of granular materials. The main silo loads are the pressures due to the stored material and to the wind, being this action the critical one when the silo is empty. Due to the high efficiency of the cylindrical form and to the high strength of the steel, these structures are thin and light-weight and, as a consequence, susceptible to the loss of local and global stability and to the pull out of the structure. With the aim to assess these effects related to the wind loading in silos, some theoretical and experimental studies were conducted. The work was carried out with aerodynamic and aeroelastic models tested in a boundary layer wind tunnel in the University of Cranfield, England, with the objective to determine the aerodynamic coefficients of the cylinder and the conical roof. The results show that the coefficients of the Brazilian Code of wind loads, NBR 6123 (1990), are adequate to the cylinder. The coefficients to the conical roof are suggested based on our tests, considering that there are no values specified by the NBR. As well it is concluded that the outside columns is on the side of safety and it is indicated the use of wind rings attached to the cylinder, which are very important to the local and global stability of the silo structure.

A influência da fuselagem sobre a posição do centro aerodinâmico da asa é complexa e deve ser considerada nos cálculos de equilíbrio e estabilidade estática longitudinal da aeronave. Este trabalho apresenta uma análise comparativa para indicar o mais preciso dentre sete métodos teóricos para prever esta influência, em condições de baixa velocidade, utilizando seis configurações de modelos de asa mais fuselagem em escala reduzida, com proporções dimensionais características da aviação leve. Mediram-se os coeficientes de momento e sustentação para cada configuração, através de ensaios em túnel de vento de baixa velocidade, circuito aberto e seção de testes fechada. Calcularam-se as posições experimentais do centro aerodinâmico através da distância do eixo de rotação da balança ao bordo de ataque da asa e derivadas do coeficiente de momento em relação ao coeficiente de sustentação. Aplicaram-se os métodos teóricos às configurações. Os resultados demonstram que a maioria dos métodos prevê comportamentos na variação da posição do centro aerodinâmico semelhantes aos obtidos experimentalmente e apontados na revisão da literatura. A análise dos resultados teóricos ante os experimentais aponta o método descrito em Engineering Sciences Data Unit (1996a) como o mais preciso. / The fuselage influence on the wing aerodynamic center is complex and must be considered within longitudinal static stability and equilibrium calculations of the airplane. This work presents a comparative analysis to indicate the most accurate between seven theoretical methods that predict this influence, at low speed conditions, using six configurations of wing-fuselage reduced scale models, with the dimensional proportions found in light aviation. The moment and lift coefficients have been measured by experiments in a low speed open circuit wind tunnel with a closed test section. The experimental aerodynamic center positions have been found by the distance of the balance trunnion to wing leading edge and the derivation of the moment coefficient relative to the lift coefficient. The theoretical methods have been applied to all configurations. The results show that most of the methods predict variations in aerodynamic center position in the same way as those obtained in experimental results and shown in the literature review. The analysis between theoretical and experimental results indicates the method from Engineering Sciences Data Unit (1996a) as the most accurate.

O presente trabalho apresenta um estudo numérico e experimental sobre o desempenho aerodinâmico de turbinas eólicas de eixo vertical envolvendo rotores Savonius convencional de duplo-estágio e helicoidal. O estudo experimental é realizado no Túnel Aerodinâmico Professor Debi Pada Sadhu, do Laboratório de Mecânica dos Fluidos da UFRGS. As simulações numéricas são realizadas com o software Fluent/ANSYS utilizando o Método dos Volumes Finitos. São comparados os coeficientes de torque estático e dinâmico, o coeficiente de potência, além de uma análise aerodinâmica das duas turbinas. As medições são realizadas empregando Tubos de Pitot, um torquímetro estático digital e um torquímetro simples construído para a medição do torque dinâmico. As turbinas são fabricadas através da técnica de prototipagem 3D, com uma semelhança de dimensões e parâmetros. As soluções numéricas são resolvidas através da equação da continuidade, das equações de Navier-Stokes com médias de Reynolds (RANS) e pelo modelo de turbulência k-ω SST. A qualidade da malha utilizada é avaliada através do método de Índice de Convergência de Malha (GCI), para três diferentes tamanhos de malha. São feitas análises dos rotores na forma estática para diferentes ângulos de incidência e com a turbina em rotação são feitas análises para diferentes razões de velocidades de ponta de pá (λ). Resultados demonstram que a turbina helicoidal apresenta um coeficiente de torque positivo para todos os ângulos do rotor, assim como a turbina convencional de dois estágios. O coeficiente de torque dinâmico da turbina helicoidal é superior ao da turbina de duplo-estágio para a maioria dos casos, e também apresenta menor oscilação de torque ao longo de cada rotação. Por consequência, o coeficiente de potência do rotor helicoidal também se tornou superior, com um valor máximo encontrado na ordem de 11,8% para um λ de 0,65 no caso experimental, e de 8,4% para o mesmo λ no caso numérico, quando comparado com o rotor de duplo-estágio. Os erros relativos entre as simulações numéricas e os resultados experimentais estão entre 2,16% e 13,4%. Uma estimativa de potência gerada é feita para ambos os casos, para uma razão de velocidade de ponta de 0,65, onde a turbina helicoidal apresenta melhores resultados em relação ao rotor de duplo-estágio, na ordem de 13,6% para uma velocidade de 10,4 m/s. / This paper presents a numerical and experimental study of vertical axis wind turbine performance comparison involving two-stage and helical Savonius rotors. The experimental study is conducted in the Aerodynamic Tunnel Professor Debi Pada Sadhu at the Fluid Mechanics Laboratory of the UFRGS. The numerical simulations are performed with the Fluent/ANSYS software using the Finite Volumes Method. The static and dynamic torque coefficients, the power coefficients, and an aerodynamic analysis of the two turbines are compared. Measurements are made using Pitot tubes, a digital static torque wrench and a simple wrench constructed for the dynamic torque measurement. The aerodynamics rotors are manufactured by 3D prototyping technique with similar dimensions and parameters. Numerical solutions are solved by the continuity equation, the Reynolds Averaged Navier-Stokes (RANS) equations and the turbulence model k-ω SST. The quality of the mesh used is evaluated used the Grid Convergence Index (GCI) method, for three different mesh sizes. The rotors analyzes are made in static form for different angles of incidence and for the rotating turbine analyzes are made for differents tip speed ratio (λ). Results show that the helical turbine has a positive static torque coefficient for any rotor angles, as well as conventional two-stage turbine. The dynamic torque coefficient of the helical turbine is higher than the two-stage turbine for most cases and also shows less torque variation along each rotation. Consequently, the power coefficient of the helical rotor also become higher, with a maximum value found on the order of 11.8% for a λ of 0.65 in the experimental case, and 8.4% for the same λ number when compared with the two-stage rotor. The relative errors between the numerical simulations and the experimental results are between 2.16% and 13.4%. A generated power estimate is made for both cases, for a tip speed ratio of 0.65, where the helical turbine provides better results compared to two-stage rotor in order of 13.6% for a velocity of 10.4 m/s.