A cross-section averaged Advection-Dispersion equation (ADE) model was developed to simulate the transport of fertilizer in furrow irrigation. The advection and dispersion processes were solved separately by implementing the method of the characteristics with cubic spline interpolation (and natural boundary condition) and weighted finite difference scheme respectively. A zero-flux boundary condition during advance and an advective gradient at the downstream end of an open furrow were established. Local pseudo-steady state was assumed in order to apply Fischer's longitudinal dispersion equation under non-uniform and unsteady furrow flow conditions. Also, several parameters were used to evaluate the ADE model and fertigation performance.A field tracer experiment in two types of downstream-end furrow and two treatments was conducted and described. Infiltration and roughness parameters were calibrated by implementing a volume balance approach. The calibrated parameters were used as input data to run the surface irrigation model (SRFR). The roughness coefficient was 0.045 for wheel and 0.055 for non-wheel furrow treatment for bare soil. The root mean square error (RMSE) comparing the computed and observed infiltrated volume was in the range of 0.09-0.38 m3. The close match between simulated and observed data indicates an acceptable calibration. Pulses of fertilizer injected at the head end of four furrows each having unique management characteristics were simulated satisfactorily during the entire duration of the irrigation event. The constant value of the longitudinal dispersion coefficient was 1 m2 min-1 and yielded an acceptable space-time evolution of the pulses of tracer injected. Similar results for the dispersion coefficient were obtained with Fischer's equation in non-uniform and unsteady stream flow conditions in the furrow. An evaluation of several fertigation strategies for furrow systems indicated that fertigation by pulses could help reduce leaching and runoff losses in surface irrigation systems.

The effectiveness of an optimization algorithm can be reduced to its ability to navigate an objective function’s topology. Hybrid optimization algorithms combine various optimization algorithms using a single meta-heuristic so that the hybrid algorithm is more robust, computationally efficient, and/or accurate than the individual algorithms it is made of. This thesis proposes a novel meta-heuristic that uses search vectors to select the constituent algorithm that is appropriate for a given objective function. The hybrid is shown to perform competitively against several existing hybrid and non-hybrid optimization algorithms over a set of three hundred test cases. This thesis also proposes a general framework for evaluating the effectiveness of hybrid optimization algorithms. Finally, this thesis presents an improved Method of Characteristics Code with novel boundary conditions, which better characterizes pipelines than previous codes. This code is coupled with the hybrid optimization algorithm in order to optimize the operation of real-world piston pumps.

The primary purpose of this research was to improve the accuracy and robustness of pipeline transient modeling. An algorithm was developed to model the transient flow in closed tubes for thin walled pipelines. Emphasis was given to the application of this type of flow to pipelines with small radius 90° elbows. An additional loss term was developed to account for the presence of 90° elbows in a pipeline. The algorithm was integrated into an optimization routine to fit results from the improved model to experimental data. A web based interface was developed to facilitate the pre- and post- processing operations. Results showed that including a loss term that represents the effects of 90° elbows in the Method of Characteristics (MOC) [1] improves the accuracy of the predicted transients by an order of magnitude. Secondary objectives of pump optimization, blockage detection and removal were investigated with promising results.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22055号 / 工博第4636号 / 新制||工||1723(附属図書館) / 京都大学大学院工学研究科都市社会工学専攻 / (主査)教授 細田 尚, 教授 戸田 圭一, 准教授 音田 慎一郎 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Power failure of pumps, sudden valve actions, and the operation of automatic control systems are all capable of generating high pressure waves in domestic water supply systems. These transient conditions resulting in high pressures can cause pipe failures by damaging valves and fittings. In this study, basic equations for solving transient analysis problems are derived using method of characteristics. Two example problems are presented. One, a single pipe system which is solved by developing an excel spreadsheet. Second, a pipe network problem is solved using transient analysis program called TRANSNET. A transient analysis program is developed in Java. This program can handle suddenly-closing valves, gradually-closing valves, pump power failures and sudden demand changes at junctions. A maximum of four pipes can be present at a junction. A pipe network problem is solved using this java program and the results were found to be similar to that obtained from TRANSNET program. The code can be further extended, for example by developing java applets and graphical user interphase to make it more user friendly. A two dimensional (2D) numerical model is developed using MATLAB to analyze gaseous cavitation in a single pipe system. The model is based on mathematical formulations proposed by Cannizzaro and Pezzinga (2005) and Pezzinga (2003). The model considers gaseous cavitation due to both thermic exhange between gas bubbles and surrounding liquid and during the process of gas release. The results from the model show that during transients, there is significant increase in fluid temperature along with high pressures. In literature pipe failures and noise problems in premise plumbing are atributed to gaseous cavitation. / Master of Science

New analytical and numerical solutions are developed to both the kinematic approximation to the St Venant equations and the Hairsine-Rose (HR) soil erosion model in order to gain a better physical understanding of soil erosion and sediment transport in shallow overland flow. The HR model is unique amongst physically based erosion models in that it is the only one that: considers the entire distribution of the soil s sediment size classes, considers the development of a layer of deposited non-cohesive sediment having different characteristics to the original underlying cohesive soil and considers separately the erosion processes of rainfall detachment, runoff entrainment and gravitational deposition. The method of characteristics and the method of lines were used to develop both the analytical and numerical solutions respectively. These solutions were obtained for boundary and initial conditions typical of those used in laboratory flume experiments along with physically realistic constant and time dependent excess rainfall rates. Depending on the boundary and initial conditions, interesting new solutions of the kinematic wave equation containing expansion waves, travelling shocks as well as solutions which split into an upslope and downslope drying profiles were found. Numerical solutions of the HR model were applied to the experimental flume data of Polyakov and Nearing (2003) obtained under flow conditions which periodically cycled between net erosion and net deposition conditions. While excellent agreement was found with suspended sediment data, the analysis suggested that an additional transport mechanisms, traditionally not included in soil erosion models, was occurring. While the inclusion of bed-load transport improved the ii overall model prediction, it was still not sufficient. Subsequent asymptotic analysis then showed that the interaction of the flow with an evolving bed morphology was in fact far more important than bed load transport. A very interesting finding from this work showed that the traditional criterion of validating sediment transport model based solely on suspended sediment data was not sufficient as reliable predictions could be obtained even when important transport mechanisms were neglected. Experimental plots of sediment discharge or suspended sediment concentration against water discharge in overland flow have been shown to contain significant hysteresis between the falling and rising limbs of the discharge hydrograph. In the final Chapter, the numerical solution developed for the complete system of soil erosion and kinematic flow was used to show that it was possible for the HR model to simulate three of the four hysteresis loops identified in the literature. Counter clock-wise loops, clock-wise loops and figure 8 loops could all be produced as a result of starting with different initial conditions, being mi(x; 0) = 0, mi(x; 0) = pimt and mi(x; 0) = 0:5pimt respectively. This is the first time that these types of hysteresis loops have been produced by any erosion model. The generation of these hysteresis loops are physically explainable in terms of sediment availability and is consistent with data obtained on the field scale.

Carregamentos transientes termo hidráulicos do tipo Steam Hammer são eventos comuns em sistemas de tubulações de vapor com grandes potenciais de catástrofes em plantas de geração de energia. Uma vez iniciado o evento, ondas de pressões são geradas com amplitudes, geralmente, de grande magnitude ocasionando altas pressões no sistema, ruídos, deformações, fadiga, com possibilidade de danos materiais e econômicos e em casos extremos fatalidades. Os procedimentos da indústria para análise deste tipo de sistema consistem realização de análises estáticas equivalentes ou análise de espectro de resposta com carregamentos caracterizados por meio de métodos analíticos baseados em hipóteses simplificadoras do fluido e fluxo. Neste trabalho é proposta a analise de sistema de tubulações por meio do método de integração numérica com superposição modal e carregamento caracterizado por método numérico com base no método das características. Comparações foram efetuadas entre os resultados obtidos pela metodologia proposta e os procedimentos da indústria, demonstrando que, dado ao alto grau de conservadorismo, os procedimentos da indústria acarretam em superdimensionamento de estruturas e tubulações ocasionando custos adicionais de projeto, sendo a otimização do projeto obtida aplicando-se a metodologia proposta no trabalho. / Steam Hammer is a common transient thermo hydraulic event in steam piping systems with potential to cause serious damages in power generation plants. It generates pressure waves, generally of great amplitude and magnitude, causing high pressures in the system, associated with noise, with possible material and economic damages and, in extreme case, even fatalities. Industry procedures for analysis of these events consists of performing equivalent static analysis, or response spectrum analysis, with transient loadings calculated by analytical methods based on assumptions of fluid and flow. This paper proposes a new methodology for the piping system analysis by the numerical integration method with modal superposition and transient loadings calculated by a numerical method based on the method of characteristics. Comparisons were made between the results obtained by the proposed methodology and the stablished industry procedures, confirming that, due to the high degree of conservatism, industry procedures can lead to additional cost to the design, with the optimization of the design being obtained by applying the methodology proposed in this paper.

Minimum miscibility pressure (MMP) is a key parameter in the design of gas flooding. There are experimental and computational methods to determine MMP. Computational methods are fast and convenient alternatives to otherwise slow and expensive experimental procedures. This research focuses on the computational aspects of MMP estimation. It investigates the shortcomings of the current computational models and offers ways to improve the robustness of MMP estimation. First, we develop a new mixing cell method of estimating MMP that, unlike previous "mixing cell" methods, uses a variable number of cells and is independent of gas-oil ratio, volume of the cells, excess oil volumes, and the amount of gas injected. The new method relies entirely on robust P-T flash calculations using any cubic equation-of-state (EOS). We show that mixing cell MMPs are comparable with those of other analytical and experimental methods, and that our mixing cell method finds all the key tie lines predicted by MOC; however, the method proved to be more robust and reliable than current analytical methods. Second, we identify a number of problems with analytical methods of MMP estimation, and demonstrate them using real oil characterization examples. We show that the current MOC results, which assume that shocks exist from one key tie line to the next may not be reliable and may lead to large errors in MMP estimation. In such cases, the key tie lines determined using the MOC method do not control miscibility, likely as a result of the onset of L₁-L₂-V behavior. We explain the problem with a simplified pseudo-ternary model and offer a procedure for determining when an error exists and for improving the results. Finally, we present a simple mathematical model for predicting the MMP of contaminated gas. Injection-gas compositions often vary during the life of a gasflood because of reinjection and mixing of fluids in situ. Determining the MMP by slim-tube or other methods for each possible variation in the gas-mixture composition is impractical. Our method gives an easy and accurate way to determine impure CO₂ MMPs for variable field solvent compositions on the basis of just a few MMPs. Alternatively, the approach could be used to estimate the enrichment level required to lower the MMP to a desired pressure. / text

Carregamentos transientes termo hidráulicos do tipo Steam Hammer são eventos comuns em sistemas de tubulações de vapor com grandes potenciais de catástrofes em plantas de geração de energia. Uma vez iniciado o evento, ondas de pressões são geradas com amplitudes, geralmente, de grande magnitude ocasionando altas pressões no sistema, ruídos, deformações, fadiga, com possibilidade de danos materiais e econômicos e em casos extremos fatalidades. Os procedimentos da indústria para análise deste tipo de sistema consistem realização de análises estáticas equivalentes ou análise de espectro de resposta com carregamentos caracterizados por meio de métodos analíticos baseados em hipóteses simplificadoras do fluido e fluxo. Neste trabalho é proposta a analise de sistema de tubulações por meio do método de integração numérica com superposição modal e carregamento caracterizado por método numérico com base no método das características. Comparações foram efetuadas entre os resultados obtidos pela metodologia proposta e os procedimentos da indústria, demonstrando que, dado ao alto grau de conservadorismo, os procedimentos da indústria acarretam em superdimensionamento de estruturas e tubulações ocasionando custos adicionais de projeto, sendo a otimização do projeto obtida aplicando-se a metodologia proposta no trabalho. / Steam Hammer is a common transient thermo hydraulic event in steam piping systems with potential to cause serious damages in power generation plants. It generates pressure waves, generally of great amplitude and magnitude, causing high pressures in the system, associated with noise, with possible material and economic damages and, in extreme case, even fatalities. Industry procedures for analysis of these events consists of performing equivalent static analysis, or response spectrum analysis, with transient loadings calculated by analytical methods based on assumptions of fluid and flow. This paper proposes a new methodology for the piping system analysis by the numerical integration method with modal superposition and transient loadings calculated by a numerical method based on the method of characteristics. Comparisons were made between the results obtained by the proposed methodology and the stablished industry procedures, confirming that, due to the high degree of conservatism, industry procedures can lead to additional cost to the design, with the optimization of the design being obtained by applying the methodology proposed in this paper.

A Ãgua à um recurso natural essencial para todas as formas de vida e a sua distribuiÃÃo deve ser realizada com qualidade e sem desperdÃcios. Um dos mÃtodos de otimizaÃÃo dos sistemas de distribuiÃÃo de Ãgua à baseado na simulaÃÃo (modelagem) de redes hidrÃulicas reais atravÃs de modelos computacionais capazes de prever o seu comportamento nas situaÃÃes diversas ao logo da sua vida Ãtil. As principais etapas desse mÃtodo sÃo calibraÃÃo; operaÃÃo e controle; projeto e otimizaÃÃo; e traÃado de redes. A ideia deste trabalho à aprimorar uma dessas tÃcnicas, a de calibraÃÃo, processo de identificaÃÃo dos parÃmetros das tubulaÃÃes (fator de atrito, rugosidade, diÃmetros e outros) em redes existentes, na qual os mesmos sÃo considerados desconhecidos. A metodologia adotada à o MÃtodo Transiente Inverso (MTI) com otimizaÃÃo da tÃcnica de seleÃÃo da soluÃÃo atravÃs do algoritmo GenÃtico (AG). O objetivo principal à calibrar os principais parÃmetros (fator de atrito e rugosidade) a fim de analisar a conveniÃncia de duas tÃcnicas: cÃlculo do fator de atrito pelo mÃtodo pelo MTI-AG e a partir da rugosidade (com uso da fÃrmula de Swamee, 1993). O estudo à realizado para duas redes sintÃticas tiradas da literatura, mas que representam sistemas reais. As condiÃÃes impostas para a anÃlise sÃo: duas manobras de vÃlvulas (lenta e brusca) responsÃveis pelo evento transiente, o monitoramento de cargas transientes em somente 20% dos nÃs das redes e a utilizaÃÃo de dois tipo de seleÃÃo de soluÃÃo do algoritmo genÃtico (com elitismo e sem elitismo). Os experimentos sÃo realizados a partir de trÃs programas: o primeiro calcula as condiÃÃes permanentes, o segundo fornece cargas transientes por meio do MÃtodo das CaracterÃsticas (MOC) na busca das soluÃÃes das equaÃÃes de movimento no escoamento transiente e o terceiro, que trabalha de forma conjugada com os demais, seleciona os melhores resultados atravÃs de iteraÃÃes realizadas conforme o algoritmo genÃtico, tÃcnica inspirada nos mecanismos de evoluÃÃo dos seres vivos. Os resultados encontrados indicam que independente das condiÃÃes impostas inicialmente à mais eficiente identificar o fator de atrito a partir das rugosidades absolutas do que calibrar esse fator pelo MTI-AG devido a grande variabilidade dos fatores de atrito durante a ocorrÃncia do evento transiente. / Water is an essential natural resource for all life forms and their distribution should be carried out with quality and without waste. One of the methods of optimization of water distribution systems is based on the simulation (modeling) of real hydraulic networks using computational models that can predict their behavior in various situations the logo of its useful life. The main steps of this method are calibration; operation and control; design and optimization; and route networks. The idea of ​​this work is to improve one such technique, the calibration parameters of the pipes identification process (friction factor, surface roughness, diameter and the like) existing in networks in which they are considered unknown. The methodology adopted is the Transient Inverse Method (MTI) with optimization of the solution selection technique by Genetic Algorithm (GA). The main objective is to calibrate the main parameters (friction and roughness factor) to analyze the convenience of two techniques: calculation of the friction factor by the method by MTI-AG and from the roughness (using the formula Swamee, 1993 ). The study is carried out for two taken synthetic networks of literature, but represent real systems. The conditions for the analysis are: two maneuvers valves (slow and abrupt) responsible for the transient event, the monitoring of transient loads in only 20% of the nodes of the networks and the use of two types of solution selection of genetic algorithm (with elitism and without elitism). The experiments are carried out through three programs: the first calculates the permanent conditions, the second provides transient loads through the method of characteristics (MOC) in the search for solutions of the equations of motion in the transient flow and the third, who works so combined with others, selects the best results through iterations performed according to the genetic algorithm, a technique inspired by the mechanisms of evolution of living beings. The results indicate that regardless of the conditions imposed is initially more efficiently identify the friction factor from the absolute roughness than calibrate this factor by MTI-AG due to the great variability of friction factors for the occurrence of the transient event.