Wakes are present in many engineering flows. These flows include internal flows such as mixing chambers and turbomachinery as well as external flows like flow over high-lift or multi-element airfoils. Many times these wakes are exposed to flow conditions such as adverse pressure gradients and streamline curvature that alter the mean flow and turbulent structure of the wake. The ability to understand how pressure gradients and streamline curvature affects the structure of the wake is essential to predicting how the wake will affect the performance of the application in which it is found. The effects of pressure gradients and curvature of low-speed wakes has been extensively documented. As the transonic flow regime is becoming of more interest as gas speeds in turbomachinery increase this work fills a void in the body of wake knowledge pertaining to curved wakes in high speed flows. An under-resolved direct numerical simulation of transonic wake flow being shed by a cambered airfoil in the presence of adverse pressure gradients and streamline curvature is therefore presented here. It was observed that the turbulence characteristics arising from the cambered airfoil that generates the wake dominate the evolution of the wake for different distances downstream depending on the component of the Reynolds stresses that is being considered. These characteristics dissipated the most quickly in the shear stresses and endured the longest in the tangential normal stresses. Previous work in low-speed wakes has indicated that curvature creates new production terms that translate into asymmetry in the profiles of the wake. Curvature was observed to have limited influence on the evolution of the streamwise normal stresses and an extensive impact on the tangential normal stresses. The transport of the Reynolds shear stresses indicate that the asymmetry in this stress is caused indeed by curvature but through turbulent diffusion and not production. The k-ε turbulence model overpredicted the effect of curvature on the turbulence stresses in the wake. This led to accelerated wake decay and spread compared to the UDNS data.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第23476号 / 工博第4888号 / 新制||工||1764(附属図書館) / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 渦岡 良介, 教授 三村 衛, 教授 肥後 陽介 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

[pt] A primeira parte deste trabalho consiste num estudo das desigualdades lineares que aparecem na síntese de funções lógicas por single-threshold. São desenvolvidas condições necessárias e suficientes para existência de solução, e também estabelecidas condições para a redução das desigualdades. Na segunda parte é proposto um método para calcular uma solução ótima para o sistema, sob certas condições de projeto. Finalmentesão apresentados métodos para realiza, com multithreshold devices, funções lógicas não realizáveis por single-threshold devices. / [en] The first part of this thesis is a theoretical study of sets of inequalities that appear in the synthesis of logical sufficient conditions are developd for existence of solution of the inequalities. In the second part, a numerical method for calculating proposed. Following this development, logical functions that cannot be realized by a single-threshold device are studied. Using the conditions developed before for single- threshold, methods are presented for realization of these functions by multithreshold devices.

The feasibility of simulating solute transport in a channel impregnated witha biofilm is investigated. Biofilm factors relevant for numerical simulation arestudied to determine a suitable range of simulation. Inside the feasable rangeseveral cases are simulated to gain insight of how different factors influence thesolute transport in and around biofilms.

This dissertation studies the effects of the "key-value-ref" model in the computational field simulation software development process. The motivation of this study is rooted in addressing the high cost of designing and implementing high-performance simulation software that runs on modern parallel supercomputers. Unlike traditional sequential programming where a number of effective tools exist, parallel super-cluster programming contains many low-level constructs that increase the complexity in the implementation of a software design. More importantly, the dynamic nature of the simulation problems brings additional challenges into the designing stage. Often a designer has to face a number of competing factors and needs to devise strategies to make a trade-off and to find better software structures that can be realized with reasonable performance and flexibility. Proper modeling can help to address many of these issues in the design and implementation stages. Using a two-phase Lagrangian particleield simulation problem as a case study, this dissertation shows that the "key-space" concept developed in the "key-value-ref" model within this dissertation is able to model the essential components in available design approaches for parallel computational field simulation, and that the model also helps to expose the design choices in a more sensible way, and also offers certain guidance towards the crafting of a better software structure. In addition, a programming interface is also designed and implemented that allows the development of computational field simulation software utilizing the "key-space" concept. Empirical results show that the current implementation provides a reasonable performance compared to those highly optimized hand-tuned programs.

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