京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第22824号 / 理博第4634号 / 新制||理||1666(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 川上 則雄, 教授 高橋 義朗, 教授 石田 憲二 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

Nonlinearity in the Navier-Stokes equations can originate from a variety of sources, such as contributions stemming from the advective term, constitutive closure models or external factors such as chemical reactions and capillarity. Needless to say, a combination of any of the above sources has the potential to exasperate the problem significantly. This dissertation explores cases that predominantly feature advective and/or capillary effects. In particular, we first consider the inertia-dominated problem of single-phase flow past a confined square cylinder, followed by a study focused on the low-Re dynamics of rigid particles straddling non-planar interfaces. The first part of the thesis investigates transient, three-dimensional, incompressible and isothermal flow of a Newtonian fluid past a symmetrically confined obstacle at zero incidence. Results from both Laser Doppler Velocimetry (LDV) experiments and direct simulations upto Re = 250 have been reported. Beyond the onset of instability (Recr ≈ 58), an inflexion point around Re ≈ 115 is detected for the Strouhal number with no evidence of hysteresis in any of the measurements. Furthermore, incommensurate frequencies observed in the range 127 ≤ Re ≤ 175 suggest a quasi-periodic transition to three-dimensionality. This is shown to be followed by an intermediate periodic window starting around Re ≈ 180. Fourier analysis and spanwise velocity correlations are then used to characterize the observed phenomena. Subsequent analysis of consolidated data suggest that only a parametric variation of transverse and spanwise blockage ratios can bring closure to the subject of bluff-body wake transitions. The second part of the thesis implements and validates a physically consistent continuum model for the Moving Contact Line (MCL) through direct simulations. After elaborately discussing the MCL conundrum, a fundamental framework for the simulations is outlined in a theoretical orientation which combines the Level set method with a Fictitious domain approach in a finite-element scheme. The thesis objectives are then realized through simulation of various case studies that show favorable comparisons with theoretical and/or published experimental data. In short, the current work successfully illustrates the potential of novel boundary conditions (such as the GNBC) to accurately describe MCL dynamics. / Chemical Engineering

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