Geophysical granular flows, such as snow avalanches, pyroclastic density currents, mudslides and debris flows, can be extremely hazardous to local populations, and understanding their complex behaviour remains an important challenge. This project aims to provide insight into these events by exploring different aspects in isolation, using a combination of mathematical theory, numerical simulations and small-scale experiments. Firstly, the effect of lateral confinement is examined by studying granular material moving in an inclined chute. This can have applications to natural releases flowing down confined valleys or conduits, and the relative simplicity of the geometry also provides a useful test case for new theoretical models. One such model is the recent depth-averaged μ(I)-rheology, which, because of the viscous terms introduced into the depth-averaged momentum balance, may be described as an intermediate approach between full constitutive laws and classical shallow-water-type equations for dense granular flows. Here, a generalisation of the new system to two spatial dimensions is described, and the resulting viscous equations are able to capture the cross-slope curvature of the downslope velocity profiles in steady uniform chute flows. This may be regarded as major progress compared to traditional hyperbolic models, which only admit constant velocity solutions. Particle size-segregation in geophysical granular flows is then investigated, which can cause important feedback on the overall bulk properties as it can lead to the development of regions with different frictional properties. A particularly striking example is segregation-induced 'finger' formation, where large particles are segregated to the flow surface and sheared to form a resistive coarse-rich front, which is unstable and spontaneously breaks down into a series of lobate structures. These travel both faster and further than one might anticipate. To model such segregation-mobility feedback effects, the depth-averaged μ(I)-rheology is extended to bidisperse flows by coupling with a depth-integrated model for size-segregation. The system of equations remains mathematically well-posed and is able to qualitatively capture finger formation, with the newly-introduced viscous terms controlling the characteristics of the leveed channels that develop. A more subtle segregation effect is studied in bidisperse roll waves, which form as small irregularities merge and coarsen as they move downslope, eventually growing into destructive large amplitude pulses. Experimental measurements show lateral, as well as vertical, segregation profiles, with the coarser grains accumulating at the fastest moving wave crests. The disturbances that form in mixtures with higher proportions of large particles grow more slowly, leading to smaller amplitude waves that travel at slower speeds, and the new coupled model predicts qualitatively similar behaviour. Finally, the influence of complex topography is investigated. A smooth two-dimensional bump is placed across the width of a chute, which, depending on the initial conditions, can lead to the formation of an airborne jet or granular shock at steady state. A simple depth-averaged model in a curvilinear coordinate system following the topography accurately captures both regimes, and represents a significant improvement on using an aligned Cartesian approach.

In turbulent water flows, large quantities of air bubbles are entrained at the free-surfaces. Practical applications of gas-liquid bubbly flows are found in Chemical, Civil, Environmental, Mechanical, Mining and Nuclear Engineering. Air-water flows are observed in small-scale as well as large-scale flow situations. Typical examples include thin circular jets used as mixing devices in chemical plants (Qw = 0.001 L/s, diameter = 1 mm) and spillway flows (Qw larger than 10,000 m3/s, flow thickness over 10 m). In each case, however, the interactions between the entrained air bubbles and the turbulence field are significant. The present manuscript regroups a collection of one book and 43 articles on the study of air bubble entrainment in turbulent flows. The work aims to gain a better understanding of the basic mechanisms of gas entrainment and the nteractions between entrained gas bubbles and the turbulence. It has been the purpose of the research work to assess critically the overall state of this field, to present new analysis and experimental results, to compare these with existing data, and to present new compelling conclusions regarding momentum and void fraction development of air-water gas-liquid bubbly flows. The manuscript presents a comprehensive analysis of the air entrainment processes in free-surface turbulent flows. The air-water flows are investigated as homogeneous mixtures with variable density. The variations of fluid density result from the non-uniform air bubble distributions and the turbulent diffusion process. Several types of air-water free-surface flows are studied : plunging jet flows, open channel flows, and turbulent water jets discharging into air.

No description available.

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2014-10-03T12:24:01Z No. of bitstreams: 2 Dissertação - Uilton Pereira da Silva Júnior - 2013.pdf: 4441880 bytes, checksum: 0e326268ea8b7a4519657530f34d0fe8 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2014-10-06T10:34:13Z (GMT) No. of bitstreams: 2 Dissertação - Uilton Pereira da Silva Júnior - 2013.pdf: 4441880 bytes, checksum: 0e326268ea8b7a4519657530f34d0fe8 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2014-10-06T10:34:13Z (GMT). No. of bitstreams: 2 Dissertação - Uilton Pereira da Silva Júnior - 2013.pdf: 4441880 bytes, checksum: 0e326268ea8b7a4519657530f34d0fe8 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2013-03-25 / The aim of this work is to study the rainfall partitions in three cultures under different soil managements: soya (Glycine max (L) Merrill) in no-tillage, corn (Zea Mays) in conventional tillage and brachiaria (brachiaria decumbens Stapf cv Comum) in no-tillage. The work was conducted from October 2011 to June 2012. This search was carried on in experimental area of the Federal University of Goias (UFG), campus Jataí, state of Goiás (Brazil). Pluviometers were installed above each culture, on the soil surface, between lines of each culture, in the soil body at 5 cm of soil depth and at 30 cm of soil depth. We used digital and handle pluviometers tools, with 3 (three) repetitions. Aimed calculating the partitions rainfall using datas given by pluviometers installed, based on numbers proposed by Kojac, et al. (2007). Worthed the precipitation intercepted by the canopy (Pf), the direct precipitation (Pd), the flow through the canopy (Ef), retained by the rain canopy (Rf), water saved in the deepth of until 5 cm of soil (Rs5), water saved in the deepth until 30 cm of soil (Rs30), runoff (RO) and the precipitation deep (Pp), over the total precipitation (Pt). To conclusion, the numbers of interceptation and saved by soya, corn and brachiaria canopy were low in negative stage, growing up with the development of foliar areas of farm. In corn culture, approximately 53% of precipitation fall down the soil of target way, in relation to total rain. In soya and brachiaria cases, the most part of rain was intercepted by the canopy before of fall down the soil, with numbers of 81,8% and 54,2% respectively. Understood that, for the three crops, only numbers of rain upper to 3 mm accepted dates of flow through the canopy. Corn presented 0,7% deep precipitation in contrast to total rains and 14% of runoff. The percentage of precipitation and runoff depth for soybeans were 7,2% and 3,7% respectively. To brachiaria was recorded 24% and 2,4% deep precipitation runoff. In tests conducted in the middle stages of vegetative brachiaria and corn, there were significant differences in precipitation retained at a depth of 30 cm soil depth in precipitation and runoff in relation to these crops. In tests conducted in the middle stages of vegetative brachiaria, and corn, there were significant differences in precipitation retained at a depth of 30 cm soil depth in precipitation and runoff. The brachiaria grown in no-till system, showed better water infiltration into the soil and less runoff. Analyzing these dates, it's possible to conclude about importance of maintenance of organic layer in the soil to reduce the runoff and elevating in the percentages of infiltration of soil water. Both the cultivated vegetable species, as the system of land management, were important in determining the values of rainfall partitions. / Este trabalho avalia as partições pluviométricas em três cultivos: soja (Glycine max (L) Merrill) cultivada no sistema de plantio direto, milho (Zea Mays) cultivado no sistema de plantio convencional e pastagem de braquiária (Brachiaria decumbens Stapf cv Comum) cultivada no sistema de plantio direto. O período de estudo foi de outubro de 2011 a junho de 2012. A pesquisa foi conduzida no campo experimental da Universidade Federal de Goiás (UFG), campus Jatobá, no município de Jataí (GO). Foram instalados instrumentos pluviométricos acima de cada cultura, sobre a superfície do solo, a 5 cm de profundidade do solo e a 30 cm de profundidade. Utilizou-se aparelhos pluviométricos manuais e digitais, com 3 repetições. Objetivou-se estimar as partições pluviométricas por meio dos dados fornecidos pelos pluviômetros instalados. Estimou-se a precipitação interceptada pelo dossel (Pf), a precipitação direta (Pd), o escoamento pelo dossel (Ef), a chuva retida pelo dossel (Rf), a água retida na profundidade de até 5 cm do solo (Rs5), a água retida na profundidade de até 30 cm do solo (Rs30), o escoamento superficial (RO) e a precipitação profunda (Pp). Os valores foram estimados em relação à precipitação total (Pt). Concluiu-se que os valores de interceptação e retenção pelo dossel da soja, milho e braquiária foram menores na fase vegetativa, aumentando conforme o desenvolvimento da área foliar dos cultivos. No cultivo do milho, 47% da precipitação foram interceptadas pelo dossel em relação à chuva total. Na soja, 81,8% da chuva foi interceptada pelo dossel antes de atingir o solo, e na braquiária 54,2%. O valor estimado da precipitação retida pelo dossel do milho foi de 28,6%, pelo dossel da soja de 22,7% e pelo dossel da braquiária de 24,7%. Verificou-se que, para os três cultivos, apenas valores de chuvas superiores a 3 mm permitiram registros de escoamento pelo dossel. O milho apresentou 0,7% de precipitação profunda em relação às chuvas totais e 14% de escoamento superficial. Os percentuais de precipitação profunda e escoamento superficial para a soja foram de 7,2% e 3,7% respectivamente. Para a braquiária, foram registrados 24% de precipitação profunda e 2,4% de escoamento superficial. Nos testes de médias realizados nas fases vegetativas da braquiária e do milho, observaram-se diferenças significativas na precipitação retida na profundidade de 30 cm do solo, na precipitação profunda e no escoamento superficial. A braquiária, cultivada no sistema de plantio direto, apresentou maior infiltração de água no solo e menor escoamento superficial em relação ao milho sob plantio convencional. Confirmando, assim, a importância da cobertura vegetal e da manutenção da camada de resíduos orgânicos no solo, para diminuição do escoamento superficial e aumento nas taxas de infiltração de água. Tanto a espécie vegetal quanto o sistema de manejo do solo foram importantes para determinar os valores das partições pluviométricas.

Made available in DSpace on 2017-07-10T17:31:12Z (GMT). No. of bitstreams: 1 Cleverson_Holocheski.pdf: 3361676 bytes, checksum: 7e3dfcfe4af0abe5639e043c72615586 (MD5) Previous issue date: 2011-08-05 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Whereas erosion is a process that detracts from the soil, reducing its productivity or even making impossible the food production in it, it is worth emphasizing the importance of studies on this topic, especially with explanations and solutions to problems found in areas that are degraded by erosive processes. The installation and evolution of this process depends on a number of factors, all of them related to the pedological cover and the shapes of slopes, such as those linked to the hydrology of the hillside. With emphasis on this type of erosion phenomenon, this work takes as its main objective to recognize the factors correlated with onset and progression of tunnels, particularly those concerning the characteristics of soils and landforms in a hillside of Rio das Pombas, in the city of Guarapuava, South Center of the Paraná State. To this end, the research was developed from a comprehensive pedological system approach, identifying and individualizing the units of soil through surveys, and also monitoring the rainfall and hydrological flows in order to observe the dynamics of subsurface water in that slope. The methodology used in the study was divided into four phases with the first phase was consisted basically of bibliographic content to be worked, then the second part of the research was carried out on field work, and in this phase samples for laboratory analysis were collected; the piezometers for monitoring of subsurface flows were installed and it was also installed the weather station to the collections related to rainfall. In the third phase, the work was focused on laboratory and office, where were then carried out the sizing analysis and also the preparation of cartographic material combined with the tabulation of data for the construction of graphs. The fourth and final phase was the analysis of integrated data, from which, through the analysis the results were achieved. In the case studied, the results indicated that the main factors of installation and maintenance of erosion of those tunnels were that related to the physical properties of pedologic cover, such as the particle size, the shape of the slope and mainly the hydrological conditions. Regarding the evolution of the erosion on that slope, it can be said that the tunnels in the future may finally become a crater, damaging the use of the area. / Considerando que a erosão é um processo que deprecia o solo diminuindo a sua produtividade ou até mesmo impossibilitando a sua produção de alimentos, cabe ressaltar, a importância de estudos sobre essa temática, principalmente, com explicações e soluções para os problemas encontrados em áreas degradadas por processos erosivos. A instalação e evolução da erosão em túneis depende de uma série de fatores, tanto aqueles relativos à cobertura pedológica e as formas das vertentes, como aqueles vinculados à hidrologia da encosta. Com destaque para esse tipo de fenômeno erosivo, o presente trabalho, adota como objetivo principal reconhecer os fatores correlacionados a instalação e evolução de túneis, particularmente, aqueles relativos às características dos solos e das formas de relevo, em uma encosta do Rio das Pombas, Município de Guarapuava, Centro Sul do Estado do Paraná. Para tanto, a pesquisa desenvolveu-se a partir de uma abordagem detalhada do sistema pedológico, identificando e individualizando as unidades de solo através de sondagens e também, monitorando as precipitações e os fluxos hidrológicos, a fim de, observar à dinâmica subsuperficial da água na referida encosta. A metodologia utilizada na pesquisa dividiu-se em quatro fases, sendo que a primeira fase consistiu basicamente no levantamento bibliográfico do conteúdo a ser trabalhado, em seguida na segunda parte da pesquisa realizou-se os trabalhos de campo, sendo que nessa fase foram coletadas as amostras para análises em laboratório; instalados os piezômetros para o monitoramento dos fluxos subsuperficiais e também instalada a estação meteorológica, para as coletas referentes às precipitações. Na terceira fase os trabalhos concentraram-se em laboratório e em gabinete, onde então foram realizadas as análises granulométricas e também a confecção do material cartográfico juntamente com a tabulação dos dados para confecção dos gráficos. Na quarta e última fase ocorreu à análise integrada dos dados, de onde então através dessa análise chegou-se aos resultados da pesquisa. No caso estudado, os resultados apontam que os principais fatores de instalação e manutenção de erosão dos túneis foram àqueles referentes às propriedades físicas da cobertura pedológica, tais como, a composição granulométrica, a forma da encosta e principalmente as condições hidrológicas. No que diz respeito à evolução do processo erosivo na referida encosta, pode-se afirmar que os túneis futuramente poderão chegar a se tornar uma voçoroca, prejudicando utilização da área.

Made available in DSpace on 2017-05-12T14:42:44Z (GMT). No. of bitstreams: 1 Cleverson_Holocheski.pdf: 3361676 bytes, checksum: 7e3dfcfe4af0abe5639e043c72615586 (MD5) Previous issue date: 2011-08-05 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Whereas erosion is a process that detracts from the soil, reducing its productivity or even making impossible the food production in it, it is worth emphasizing the importance of studies on this topic, especially with explanations and solutions to problems found in areas that are degraded by erosive processes. The installation and evolution of this process depends on a number of factors, all of them related to the pedological cover and the shapes of slopes, such as those linked to the hydrology of the hillside. With emphasis on this type of erosion phenomenon, this work takes as its main objective to recognize the factors correlated with onset and progression of tunnels, particularly those concerning the characteristics of soils and landforms in a hillside of Rio das Pombas, in the city of Guarapuava, South Center of the Paraná State. To this end, the research was developed from a comprehensive pedological system approach, identifying and individualizing the units of soil through surveys, and also monitoring the rainfall and hydrological flows in order to observe the dynamics of subsurface water in that slope. The methodology used in the study was divided into four phases with the first phase was consisted basically of bibliographic content to be worked, then the second part of the research was carried out on field work, and in this phase samples for laboratory analysis were collected; the piezometers for monitoring of subsurface flows were installed and it was also installed the weather station to the collections related to rainfall. In the third phase, the work was focused on laboratory and office, where were then carried out the sizing analysis and also the preparation of cartographic material combined with the tabulation of data for the construction of graphs. The fourth and final phase was the analysis of integrated data, from which, through the analysis the results were achieved. In the case studied, the results indicated that the main factors of installation and maintenance of erosion of those tunnels were that related to the physical properties of pedologic cover, such as the particle size, the shape of the slope and mainly the hydrological conditions. Regarding the evolution of the erosion on that slope, it can be said that the tunnels in the future may finally become a crater, damaging the use of the area. / Considerando que a erosão é um processo que deprecia o solo diminuindo a sua produtividade ou até mesmo impossibilitando a sua produção de alimentos, cabe ressaltar, a importância de estudos sobre essa temática, principalmente, com explicações e soluções para os problemas encontrados em áreas degradadas por processos erosivos. A instalação e evolução da erosão em túneis depende de uma série de fatores, tanto aqueles relativos à cobertura pedológica e as formas das vertentes, como aqueles vinculados à hidrologia da encosta. Com destaque para esse tipo de fenômeno erosivo, o presente trabalho, adota como objetivo principal reconhecer os fatores correlacionados a instalação e evolução de túneis, particularmente, aqueles relativos às características dos solos e das formas de relevo, em uma encosta do Rio das Pombas, Município de Guarapuava, Centro Sul do Estado do Paraná. Para tanto, a pesquisa desenvolveu-se a partir de uma abordagem detalhada do sistema pedológico, identificando e individualizando as unidades de solo através de sondagens e também, monitorando as precipitações e os fluxos hidrológicos, a fim de, observar à dinâmica subsuperficial da água na referida encosta. A metodologia utilizada na pesquisa dividiu-se em quatro fases, sendo que a primeira fase consistiu basicamente no levantamento bibliográfico do conteúdo a ser trabalhado, em seguida na segunda parte da pesquisa realizou-se os trabalhos de campo, sendo que nessa fase foram coletadas as amostras para análises em laboratório; instalados os piezômetros para o monitoramento dos fluxos subsuperficiais e também instalada a estação meteorológica, para as coletas referentes às precipitações. Na terceira fase os trabalhos concentraram-se em laboratório e em gabinete, onde então foram realizadas as análises granulométricas e também a confecção do material cartográfico juntamente com a tabulação dos dados para confecção dos gráficos. Na quarta e última fase ocorreu à análise integrada dos dados, de onde então através dessa análise chegou-se aos resultados da pesquisa. No caso estudado, os resultados apontam que os principais fatores de instalação e manutenção de erosão dos túneis foram àqueles referentes às propriedades físicas da cobertura pedológica, tais como, a composição granulométrica, a forma da encosta e principalmente as condições hidrológicas. No que diz respeito à evolução do processo erosivo na referida encosta, pode-se afirmar que os túneis futuramente poderão chegar a se tornar uma voçoroca, prejudicando utilização da área.

Ein neues, verallgemeinertes Modell für Blasenkoaleszenz und –zerfall wurde entwickelt. Es basiert auf physikalischen Überlegungen und berücksichtigt verschiedene Mechanismen, die zu Blasenkoaleszenz und –zerfall führen können. In einer ausführlichen Literaturrecherche wurden zunächst die verfügbaren Modelle zusammengestellt und analysiert. Es zeigte sich, dass viele widersprüchliche Modelle veröffentlicht wurden. Keins dieser Modelle erlaubt die Vorhersage der Entwicklung der Blasengrößenverteilungen entlang einer Rohrströmung für einen breiten Bereich an Kombinationen von Volumenströmen der Gas- und der Flüssigphase. Das neue Modell wurde ausführlich in einem vereinfachten Testsolver untersucht. Dieser erfasst zwar nicht alle Einzelheiten einer sich entlang des Rohres entwickelten Strömungen, erlaubt aber im Gegensatz zu den CFD-Simulationen eine Vielzahl von Variationsrechnungen zur Untersuchung des Einflusses einzelner Größen und Modelle. Koaleszenz und Zerfall kann nicht getrennt von anderen Phänomenen und Modellen, die diese widerspiegeln, betrachtet werden. Es bestehen enge Wechselwirkungen mit der Turbulenz der Flüssigphase und dem Impulsaustausch zwischen den Phasen. Da die Dissipationsrate der turbulenten kinetischen Energie ein direkter Eingangsparameter für das neue Modell ist, wurde die Turbulenzmodellierung besonders genau untersucht. Zur Validierung des Modells wurde eine TOPFLOW-Experimentalserie zur Luft-Wasser-Strömungen in einem 8 m langen DN200-Rohr genutzt. Die Daten zeichnen sich durch eine hohe Qualität aus und wurden im Rahmen des TOPFLOW-IIVorhabens mit dem Ziel eine Grundlage für die hier vorgestellten Arbeiten zu liefern, gewonnen. Die Vorhersage der Entwicklung der Blasengrößenverteilung entlang des Rohrs konnte im Vergleich zu den bisherigen Standardmodellen für Blasenkoaleszenz und -zerfall in CFX deutlich verbessert werden. Einige quantitative Abweichungen bleiben aber bestehen. Die vollständigen Modellgleichungen sowie eine Implementierung über „User-FORTRAN“ in CFX stehen zur Verfügung und können für weitere Arbeiten zur Simulation polydisperser Blasenströmungen genutzt werden.

Bed topography identification in open channel and glacier flows is of paramount importance for the study of the respective flows. In the former, the knowledge of the channel bed topography is required for modelling the hydrodynamics of open channel flows, fluvial hydraulics, flood propagation, and river flow monitoring. Indeed, flow models based on the Shallow Water Approximation require prior information on the channel bed topography to accurately capture the flow features. While in the latter, usable bedrock topographic information is very important for glacier flow modellers to accurately predict the flow characteristics. Experimental techniques to infer the bed topography are usually used but are mostly time consuming, costly, and sometimes not possible due to geographical restrictions. However, the measurement of free surface elevation is relatively easy. Alternative to experimental techniques, it is therefore important to develop fast, easy-to-implement, and cost-effective numerical methods. The inverse of the classical hydrodynamic problem corresponds to the determination of hydraulic parameters from measurable quantities. The forward problem uses model parameters to determine measurable quantities. New one-shot and direct pseudo-analytical and numerical approaches for reconstructing the channel bed topography from known free surface elevation data is developed for one-dimensional shallow water flows. It is shown in this work that instead of treating this inverse problem in the traditional partial differential equation (PDE)-constrained optimization framework, the governing equations of the direct problem can be conveniently rearranged to obtain an explicit PDE for the inverse problem. This leads to a direct solution of the inverse problem which is successfully tested on a range of benchmark problems and experimental data for noisy and noiseless free surface data. It was found that this solution approach creates very little amplification of noise. A numerical technique which uses the measured free surface velocity to infer the channel bed topography is also developed. The one-dimensional shallow water equations along with an empirical relationship between the free surface and the depth averaged velocities are used for the inverse problem analysis. It is shown that after a series of algebraic manipulation and integration, the equation governing the inverse problem simplifies to a simple integral equation. The proposed method is tested on a range of analytical and experimental benchmark test cases and the results confirm that, it is possible to reconstruct the channel bed topography from a known free surface velocity distribution of one-dimensional open channel flows. Following the analysis of the case of one-dimensional shallow water flows, a numerical technique for reconstructing the channel bed topography from known free surface elevation data for steep open channel flows is developed using a modified set of equations for which the zero-inertia shallow water approximation holds. In this context, the shallow water equations are modified by neglecting inertia terms while retaining the effects of the bed slope and friction terms. The governing equations are recast into a single first-order partial differential equation which describes the inverse problem. Interestingly, the analysis shows that the inverse problem does not require the knowledge of the bed roughness. The forward problem is solved using MacCormack’s explicit numerical scheme by considering unsteady modified shallow water equations. However, the inverse problem is solved using the method of characteristics. The results of the inverse and the forward problem are successfully tested against each other. In the framework of full two-dimensional shallow water equations, an easy-to-implement and fast to solve direct numerical technique is developed to solve the inverse problem of shallow open channel flows. The main underlying idea is analogous to the idea implemented for the case of one-dimensional reconstruction. The technique described is a “one-shot technique” in the sense that the solution of the partial differential equation provides the solution to the inverse problem directly. The idea is tested on a set of artificial data obtained by first solving the forward problem. Glaciers are very important as an indicator of future climate change or to trace past climate. They respond quickly compared to the Antarctica and Greenland ice sheets which make them ideal to predict climate changes. Glacier bedrock topography is an important parameter in glacier flow modelling to accurately capture its flow dynamics. Thus, a mathematical technique to infer this parameter from measured free surface data is invaluable. Analogous to the approaches implemented for open channel flows, easy-to-implement direct numerical and analytical algorithms are developed to infer the bedrock topography from the knowledge of the free surface elevation in one space dimension. The numerical and analytical methods are both based on the Shallow Ice Approximation and require the time series of the ablation/accumulation rate distribution. Moreover, the analytical method requires the knowledge of a non-zero glacier thickness at an arbitrary location. Numerical benchmark test cases are used to verify the suitability and applicability of the algorithms.

Ein neues, verallgemeinertes Modell für Blasenkoaleszenz und –zerfall wurde entwickelt. Es basiert auf physikalischen Überlegungen und berücksichtigt verschiedene Mechanismen, die zu Blasenkoaleszenz und –zerfall führen können. In einer ausführlichen Literaturrecherche wurden zunächst die verfügbaren Modelle zusammengestellt und analysiert. Es zeigte sich, dass viele widersprüchliche Modelle veröffentlicht wurden. Keins dieser Modelle erlaubt die Vorhersage der Entwicklung der Blasengrößenverteilungen entlang einer Rohrströmung für einen breiten Bereich an Kombinationen von Volumenströmen der Gas- und der Flüssigphase. Das neue Modell wurde ausführlich in einem vereinfachten Testsolver untersucht. Dieser erfasst zwar nicht alle Einzelheiten einer sich entlang des Rohres entwickelten Strömungen, erlaubt aber im Gegensatz zu den CFD-Simulationen eine Vielzahl von Variationsrechnungen zur Untersuchung des Einflusses einzelner Größen und Modelle. Koaleszenz und Zerfall kann nicht getrennt von anderen Phänomenen und Modellen, die diese widerspiegeln, betrachtet werden. Es bestehen enge Wechselwirkungen mit der Turbulenz der Flüssigphase und dem Impulsaustausch zwischen den Phasen. Da die Dissipationsrate der turbulenten kinetischen Energie ein direkter Eingangsparameter für das neue Modell ist, wurde die Turbulenzmodellierung besonders genau untersucht. Zur Validierung des Modells wurde eine TOPFLOW-Experimentalserie zur Luft-Wasser-Strömungen in einem 8 m langen DN200-Rohr genutzt. Die Daten zeichnen sich durch eine hohe Qualität aus und wurden im Rahmen des TOPFLOW-IIVorhabens mit dem Ziel eine Grundlage für die hier vorgestellten Arbeiten zu liefern, gewonnen. Die Vorhersage der Entwicklung der Blasengrößenverteilung entlang des Rohrs konnte im Vergleich zu den bisherigen Standardmodellen für Blasenkoaleszenz und -zerfall in CFX deutlich verbessert werden. Einige quantitative Abweichungen bleiben aber bestehen. Die vollständigen Modellgleichungen sowie eine Implementierung über „User-FORTRAN“ in CFX stehen zur Verfügung und können für weitere Arbeiten zur Simulation polydisperser Blasenströmungen genutzt werden.

京都大学 / 0048 / 新制・論文博士 / 博士(農学) / 乙第13021号 / 論農博第2831号 / 新制||農||1042(附属図書館) / 学位論文||H28||N4967(農学部図書室) / 32949 / 京都大学大学院農学研究科地域環境科学専攻 / (主査)教授 藤原 正幸, 教授 村上 章, 准教授 宇波 耕一 / 学位規則第4条第2項該当 / Doctor of Agricultural Science / Kyoto University / DFAM