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The aerodynamic design and optimization of a wing-fuselage junction fillet as part of a multi-disciplinary optimization process during the early aircraft design stagesHadjiilias, Hippokrates A. January 1996 (has links)
An attempt to minimize interference drag in a wing-fuselage junction by means of inserting a fillet is presented in this thesis. The case of a low-wing com- mercial transport aicraft at cruise conditions is examined. Due to the highly three dimensional behaviour of the flow field around the junction, a thin-layer Navier-Stokes code was implemented to estimate the drag forces at the junc- tion. Carefully selected design variable combinations based on-the theory of Design of Experiments constituted the initial group of feasible cases for which the flow solver had to be run. The drag values of these feasible cases were then used to create a second order response surface which could predict with rea- sonable accuracy the interference drag given the value of the design variables within the feasible region. A further optimization isolated the minimum in- terference drag combination of design variable values within the design space. The minimurn interference drag combination of design variable values was eval- uated numerically by the flow solver. The prediction of the response surface and the numerical value obtained by the flow solver for the interference drag of the optimal wing-fuselage combination differed by less than five percent. To demonstrate the ability of the method to be used in an interdisciplinary analysis and optimization program, a landing gear design module is included which provides volume constraints on the fillet geometry during the fillet sur- face definition phase. The Navier Stokes flow analyses were performed on the Cranfield Cray su- percomputer. Each analysis required between eight to twelve CPU hours, and the total CPU time required for the optimization of the six variable model described in the thesis required thirty Navier Stokes runs implementing the Design of Experimens and Surface Response Methodology implementation. For comparison, a typical optimization implementing a classical conjugate di- rections optimizer with no derivative information available would probably require more than forty iterations. Both the optimization and the flow solver results are discussed and some recommendations for improving the efficiency of the code and for further ap- plications of the method are given.
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Reliability-Based Optimization of Anisotropic Cylinders with Response Surface Approximation of Axial Buckling LoadSu, Bin 14 December 2001 (has links)
The reliability analysis and reliability-based optimization of laminated circular cylinders under axial buckling instability are studied. Structural reliability is measured in terms of Hasofer-Lind reliability index. The response surface models are used in both the calculation of the reliability index and the reliability-based optimization. In reliability analysis, both deterministic and probabilistic sensitivity factors are investigated; the results show that the reliability index is most sensitive to the applied load and Young's modulus of the material. Two cases are considered in the optimization study. In the first case, the cylinder weight is minimized subject to a reliability constraint whereas in the second case, cylinder reliability is maximized subject to a weight constraint. In addition, two different optimization techniques are studied. In the first technique, a global response surface model of the buckling response based on 3000 Monte Carlo simulations is used for the design optimization whereas in the second technique, multiple local regression models, with each based on approximately 20 simulations, are used in sequential search of an optimum design. An optimum design is found. The results based on sequential application of multiple local regression models are close to those from global optimization while the former is much more efficient in terms of computational cost.
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Estudo da influência dos parâmetros de injeção de combustível no ruído emitido por motores diesel, fazendo uso do planejamento multivariado de experimentos / Study of the influence of the fuel injection parameters on the noise emitted by diesel engines, using the multivariate design of experimentsRodrigues, Marlon Casagrande 06 October 2011 (has links)
Orientador: Roy Edward Bruns / Dissertação (mestrado profissional) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-18T11:44:59Z (GMT). No. of bitstreams: 1
Rodrigues_MarlonCasagrande_M.pdf: 2084739 bytes, checksum: 4206c434cf21dfc145d73ca304a9981b (MD5)
Previous issue date: 2011 / Resumo: Nos últimos anos a emissão de ruído tem sido decisiva para aceitação de veículos no mercado, não somente devido a legislação, mas também no que diz respeito a satisfação do cliente. Por este motivo as empresas fabricantes de veículos e ou motores de combustão interna tem sido obrigadas a dar uma atenção especial as emissões de ruído para poderem competir com suas concorrentes. Neste trabalho realizou-se estudo da influencia dos parâmetros de injeção de combustível do motor MWM 6.12 TCE no nível de ruído emitido pelo motor Diesel na condição de marcha lenta, por meio da técnica de planejamento multivariado de experimentos. Foram escolhidas duas técnicas de medição indireta de ruído (ruído de combustão e aceleração na saia do bloco) para serem utilizadas como variável resposta do planejamento de experimentos. Para verificação da eficácia dos planejamentos realizou-se ensaios qualitativos e quantitativos de ruído propriamente dito. Foi feito um planejamento fatorial fracionário 28-4 para fazer uma triagem de oito fatores de acordo com seus efeitos nas respostas aceleração na saia do bloco e ruído de combustão. Os fatores com efeitos mais significativos, pressão do rail, ponto de injeção principal, ponto de pré-injeção 2 e debito da pré-injeção 2, foram investigados usando um planejamento composto central e superfícies de respostas foram determinadas para cada uma das respostas. Os resultados mostraram que apenas a variável resposta vibração na saia do bloco apresentou resultados satisfatórios para esta condição especifica do motor tanto nos testes quantitativos como qualitativos (redução de 2 dB e melhora na qualidade sonora respectivamente). Apos verificação da influencia dos parâmetros de injeção no ruído emitido verificou-se também a influencia destas alterações no consumo de combustível e emissões dos gases de escape e foi observado que existem influencias significativas nas emissões dos gases de escape / Abstract: In recent years the noise level has been decisive for acceptance of vehicles on the market, not only because of legislation but also with regard to customer satisfaction. For this reason the manufacturers of vehicles and internal combustion engines have been forced to give special attention to the emission of noise to compete with their competitors. In this work, the influences of fuel injection parameters on the noise level of the MWM 6.12 TCE diesel engine emitted under low idle condition were determined using multivariate statistical design of experiments. Two techniques for the indirect measurement of noise, combustion noise and engine crankcase vibration, were chosen as the response variables for the experimental design. To check design effectiveness both qualitative and quantitative noise measurements were carried out. A 28-4 fractional factorial design was performed to screen eight factors according to their effects on engine crankcase vibration, and combustion noise. The factors with the most significant effects, rail pressure, pre-injection point, main injection point and the pre-injection delivery, were investigated using a central composite design and response surfaces were determined for each response. The results showed that only the engine crankcase vibration showed satisfactory results for this particular engine condition in both the quantitative and qualitative analyses (reduction of 2 dB and an improvement in sound quality, respectively). After verification of the influences of the injection parameters on the noise the influences of these changes on fuel consumption and exhaust emissions were also analyzed. Significant influences were observed on the exhaust gas emissions / Mestrado / Projetos / Mestre em Engenharia Automobilistica
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A novel reliability evaluation method for large engineering systemsFarag, Reda, Haldar, Achintya 06 1900 (has links)
A novel reliability evaluation method for large nonlinear engineering systems excited by dynamic loading applied in time domain is presented. For this class of problems, the performance functions are expected to be function of time and implicit in nature. Available first-or second-order reliability method (FORM/SORM) will be challenging to estimate reliability of such systems. Because of its inefficiency, the classical Monte Carlo simulation (MCS) method also cannot be used for large nonlinear dynamic systems. In the proposed approach, only tens instead of hundreds or thousands of deterministic evaluations at intelligently selected points are used to extract the reliability information. A hybrid approach, consisting of the stochastic finite element method (SFEM) developed by the author and his research team using FORM, response surface method (RSM), an interpolation scheme, and advanced factorial schemes, is proposed. The method is clarified with the help of several numerical examples. (C) 2016 Faculty of Engineering, Ain Shams University. Production and hosting by Elsevier B.V.
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Single-Step Factor Screening and Response Surface Optimization Using Optimal Designs with Minimal AliasingTruong, David Hien 05 May 2010 (has links)
Cheng and Wu (2001) introduced a method for response surface exploration using only one design by using a 3-level design to first screen a large number of factors and then project onto the significant factors to perform response surface exploration. Previous work generally involved selecting designs based on projection properties first and aliasing structure second. However, having good projection properties is of little concern if the correct factors cannot be identified. We apply Jones and Nachtsheim’s (2009) method for finding optimal designs with minimal aliasing to find 18, 27, and 30-run designs to use for single-step screening and optimization. Our designs have better factor screening capabilities than the designs of Cheng and Wu (2001) and Xu et al. (2004), while maintaining similar D-efficiencies and allowing all projections to fit a full second order model.
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Multivariate Optimization of Neutron Detectors Through ModelingWilliamson, Martin Rodney 01 December 2010 (has links)
Due to the eminent shortage of 3He, there exists a significant need to develop a new (or optimize an existing) neutron detection system which would reduce the dependency on the current 3He-based detectors for Domestic Nuclear Detection Office (DNDO) applications. The purpose of this research is to develop a novel methodology for optimizing candidate neutron detector designs using multivariate statistical analysis of Monte Carlo radiation transport code (MCNPX) models. The developed methodology allows the simultaneous optimization of multiple detector parameters with respect to multiple response parameters which measure the overall performance of a candidate neutron detector. This is achieved by applying three statistical strategies in a sequential manner (namely factorial design experiments, response surface methodology, and constrained multivariate optimization) to results generated from MCNPX calculations. Additionally, for organic scintillators, a methodology incorporating the light yield non-proportionality is developed for inclusion into the simulated pulse height spectra (PHS). A Matlab® program was developed to post-process the MCNPX standard and PTRAC output files to automate the process of generating the PHS thus allowing the inclusion of nonlinear light yield equations (Birks equations) into the simulation of the PHS for organic scintillators.
The functionality of the developed methodology is demonstrated on the successful multivariate optimization of three neutron detection systems which utilize varied approaches to satisfying the DNDO criteria for an acceptable alternative neutron detector. The first neutron detection system optimized is a 3He-based radiation portal monitor (RPM) based on a generalized version of a currently deployed system. The second system optimized is a 6Li-loaded polymer composite scintillator in the form of a thin film. The final system optimized is a 10B-based plastic scintillator sandwiched between two standard plastic scintillators. Results from the multivariate optimization analysis include not only the identification of which factors significantly affect detector performance, but also the determination of optimum levels for those factors with simultaneous consideration of multiple detector performance responses. Based on the demonstrated functionality of the developed multivariate optimization methodology, application of the methodology in the development process of new candidate neutron detector designs is warranted.
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An Examination of the Information Content of Funds from Operations (FFO) Using Polynomial Regression and Response Surface MethodologyGyamfi-Yeboah, Frank 22 July 2010 (has links)
I examine the market reaction to the announcement of FFO by REITs using abnormal trading volume as a gauge of investors’ reaction. I also address the question of whether FFO provides more useful information to investors than net income. Lastly, I examine whether the quality of private information among traders prior to the announcement of FFO affects the level of abnormal trading volume.
Using three different specifications, I find that even though the announcement of FFO leads to abnormal trading, there is no association between the level of abnormal trading volume and the size of the surprise contained in the FFO announcement. I also find, using abnormal returns as a measure of investor response, that FFO explains significantly more variance in abnormal returns than net income suggesting that FFO provides more useful information than net income.
Lastly, I use the proportion of institutional holdings as a proxy for the number of informed traders to predict the amount of abnormal trading volume. I find no significant relation between abnormal trading volume and the proportion of institutional holdings. However, when I break down institutional ownership into two broad classifications, I find that the level of abnormal trading volume is significantly positively related to the holdings by mutual funds and investment advisors but negatively related to the holdings of other institutions (pension funds &.endowments, banks and insurance companies). This raises questions of whether the use of an aggregate measure of institutional ownership is appropriate in studies that examine the effect of institutional holdings.
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Design/Evaluation of A Methodology For Performance Optimization Of Indexable Carbide InsertsYah, Fritz Alum January 2009 (has links)
In this project, two broad facets in the design of a methodology for performance optimization of indexable carbide inserts were examined. They were physical destructive testing and software simulation.For the physical testing, statistical research techniques were used for the design of the methodology. A five step method which began with Problem definition, through System identification, Statistical model formation, Data collection and Statistical analyses and results was indepthly elaborated upon. Set-up and execution of an experiment with a compression machine together with roadblocks and possible solution to curb road blocks to quality data collection were examined. 2k factorial design was illustrated and recommended for process improvement. Instances of first-order and second-order response surface analyses were encountered. In the case of curvature, test for curvature significance with center point analysis was recommended. Process optimization with method of steepest ascent and central composite design or process robustness studies of response surface analyses were also recommended.For the simulation test, AdvantEdge program was identified as the most used software for tool development. Challenges to the efficient application of this software were identified and possible solutions proposed. In conclusion, software simulation and physical testing were recommended to meet the objective of the project.
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Design Optimization and Combustion Simulation of Two Gaseous and Liquid-Fired CombustorsHajitaheri, Sina January 2012 (has links)
The growing effect of combustion pollutant emission on the environment and increasing petroleum prices are driving development of design methodologies for clean and efficient industrial combustion technologies. The design optimization methodology employs numerical algorithms to find the optimal solution of a design problem by converting it into a multivariate minimization problem. This is done by defining a vector of design parameters that specifies the design configuration, and an objective function that quantifies the performance of the design, usually so the optimal design outcome minimizes the objective function. A numerical algorithm is then employed to find the design parameters that minimize the objective function; these parameters thus specify the optimal design. However this technique is used in several other fields of research, its application to industrial combustion is fairly new.
In the present study, a statistical optimization method called response surface methodology is connected to a CFD solver to find the highest combustion efficiency by changing the inlet air swirl number and burner quarl angle in a furnace. OpenFOAM is used to model the steady-state combustion of natural gas in the 300 KW BERL combustor. The main barrier to applying optimization in the design of industrial combustion equipment is the substantial computational effort needed to carry out the CFD simulation every time the objective function needs to be evaluated. This is intensified by the stiffness of the coupled governing partial differential equations, which can cause instability and divergent simulations. The present study addresses both of these issues by initializing the flow field for each objective function evaluation with the numerical results of the previously converged point. This modification dramatically reduced computation time.
The combustion of diesel spray in the GenTex 50M process heater is investigated in the next part of this thesis. Experimental and numerical studies were carried out for both the cold spray and the diesel combustion where the numerical results satisfactorily predicted the observations. The simulation results show that, when carrying out a parametric design of a liquid fuel-fired combustor it is necessary to consider the effect of design parameters on the spray aerodynamic characteristics and size distribution, the air/spray interactions, and the size of the recirculation zones.
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Design Optimization and Combustion Simulation of Two Gaseous and Liquid-Fired CombustorsHajitaheri, Sina January 2012 (has links)
The growing effect of combustion pollutant emission on the environment and increasing petroleum prices are driving development of design methodologies for clean and efficient industrial combustion technologies. The design optimization methodology employs numerical algorithms to find the optimal solution of a design problem by converting it into a multivariate minimization problem. This is done by defining a vector of design parameters that specifies the design configuration, and an objective function that quantifies the performance of the design, usually so the optimal design outcome minimizes the objective function. A numerical algorithm is then employed to find the design parameters that minimize the objective function; these parameters thus specify the optimal design. However this technique is used in several other fields of research, its application to industrial combustion is fairly new.
In the present study, a statistical optimization method called response surface methodology is connected to a CFD solver to find the highest combustion efficiency by changing the inlet air swirl number and burner quarl angle in a furnace. OpenFOAM is used to model the steady-state combustion of natural gas in the 300 KW BERL combustor. The main barrier to applying optimization in the design of industrial combustion equipment is the substantial computational effort needed to carry out the CFD simulation every time the objective function needs to be evaluated. This is intensified by the stiffness of the coupled governing partial differential equations, which can cause instability and divergent simulations. The present study addresses both of these issues by initializing the flow field for each objective function evaluation with the numerical results of the previously converged point. This modification dramatically reduced computation time.
The combustion of diesel spray in the GenTex 50M process heater is investigated in the next part of this thesis. Experimental and numerical studies were carried out for both the cold spray and the diesel combustion where the numerical results satisfactorily predicted the observations. The simulation results show that, when carrying out a parametric design of a liquid fuel-fired combustor it is necessary to consider the effect of design parameters on the spray aerodynamic characteristics and size distribution, the air/spray interactions, and the size of the recirculation zones.
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