Regional deposition and ventilation of particles by generation, lobe and lung during steady inhalation in a computed tomography (CT) based human airway model are investigated numerically. The airway model consists of a seven-generation human airway tree, with oral cavity, pharynx and larynx. The turbulent flow in the upper respiratory tract is simulated by large-eddy simulation. The flow boundary conditions at the peripheral airways are derived from CT images at two lung volumes to produce physiologically-realistic regional ventilation. Particles with diameter less than 2.5 microns are selected for study because smaller particles tend to penetrate to the more distal parts of the lung. The current generational particle deposition efficiencies agree well with existing measurement data. Generational deposition efficiencies exhibit similar dependence on particle Stokes number regardless of generation, whereas deposition and ventilation efficiencies vary by lobe and lung, depending on airway morphology and airflow ventilation. In particular, regardless of particle size, the left lung receives a greater proportion of the particle bolus as compared to the right lung in spite of greater flow ventilation to the right lung. This observation is supported by the left-right lung asymmetry of particle ventilation observed in medical imaging. It is found that the particle-laden turbulent laryngeal jet flow, coupled with the unique geometrical features of the airway, causes a disproportionate amount of particles to enter the left lung.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22894号 / 工博第4791号 / 新制||工||1749(附属図書館) / 京都大学大学院工学研究科原子核工学専攻 / (主査)教授 横峯 健彦, 教授 佐々木 隆之, 講師 河原 全作 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

Understanding the dynamics of micro- and nanometer-sized objects like molecules, particles, and living cells in biological systems and biomaterials has become a key component in biomedical research. Consequently, significant progress has been made for the development of imaging platforms, fluorescent probes, and computational tools to visualize and quantify biological processes at different length and time scales. However, despite such advances, achieving a reliable measurement accuracy on the dynamic behavior of these microscopic vehicles in diverse biological contexts is challenging. Subsequently, the motivation behind this dissertation is to develop new robust microfluidic velocimetry techniques to investigate molecular transport and cell migration within an in-vitro microfluidic platform.

This study was concerned with the most common reverse flow type of cyclones where the flow enters the cyclone through a tangential inlet and leaves via an axial outlet pipe at the top of the cyclone. Numerical computations of two different cyclones were based on the so-called Stairmand cyclone. The difference in geometry between these two cyclones was basically characterized by the geometrical swirl number Sg of 3.5 and 4. Turbulent secondary flows inside a straight square channel have been studied numerically by using Large Eddy Simulation (LES) in order to verify the implementation process. Prandtl’s secondary motion calculated by LES shows satisfying agreement with both, Direct Numerical Simulation (DNS) and experimental results. Numerical calculations were carried out at various axial positions and at the apex cone of a gas cyclone separator. Two different NS-solvers (a commercial one, and a research code), based on a pressure correction algorithm of the SIMPLE method have been applied to predict the flow behavior. The flow was assumed as unsteady, incompressible and isothermal. A k − epsilon turbulence model has been applied first using the commercial code to investigate the gas flow. Due to the nature of cyclone flows, which exhibit highly curved streamlines and anisotropic turbulence, advanced turbulence models such as RSM (Reynolds Stress Model) and LES (Large Eddy Simulation) have been used as well. The RSM simulation was performed using the commercial package CFX4.4, while for the LES calculations the research code MISTRAL/PartFlow-3D code developed in our multiphase research group has been applied utilizing the Smagorinsky model. It was found that the k − epsilon model cannot predict flow phenomena inside the cyclone properly due to the strong curvature of the streamlines. The RSM results are comparable with LES results in the area of the apex cone plane. However, the application of the LES reveals qualitative agreement with the experimental data, but requires higher computer capacity and longer running times than RSM. These calculations of the continuous phase flow were the basis for modeling the behavior of the solid particles in the cyclone separator. Particle trajectories, pressure drop and the cyclone separation efficiency have been studied in some detail. This thesis is organized into five chapters. After an introduction and overview, chapter 2 deals with continuous phase flow turbulence modeling including the governing equations. The emphasis will be based on LES modelling. Furthermore, the disperse phase motion is treated in chapter 3. In chapter 4, the validation process of LES implementation with channel flow is presented. Moreover, prediction profiles of the gas flow are presented and discussed. In addition, disperse phase flow results are presented and discussed such as particle trajectories; pressure drop and cyclone separation efficiency are also discussed. Chapter 5 summarizes and concludes the thesis.

No description available.

Diabetes has gained growing attendance as one of the key non communicable diseases (NCD) with the World Health Organization identifying it as the focus of the World Health Day 2016. It is reported that more than 420 million people suffer from diabetes, a number predicted to rise in the coming years. This report forms part of a broader, long term focus project that aims to establish a systems approach to type 2 diabetes (T2D), the variant that accounts for more than 90% of reported diabetes cases. The broader project objectives are to identify possible biomarkers for the onset and the progression of T2D as a precursor to enable potential future approaches to delay onset, or even reverse disease states, via active bio-compounds and/or establishment of beneficial nutritional patterns. The 6-month master’s work reported here is sub-project that focused specifically on cell level vesicle trafficking processes. These processes are believed to be crucial in understanding the formation amyloid plaques, which compromise or kill the insulin secreting beta cells. Up until now, there has been a lack of appropriate experimental techniques to directly observe this process in live cells.  Hence we have developed 2 new techniques: (i)               a method of imaging the actin and tubulin network reorganization during exocytosis of the insulin containing granules while exploring novel ways of characterizing the network. (ii)             a method of imaging the granules themselves and using particle tracking microrheology to analyze their movement patterns during stimulation with glucose. These new techniques open the door to follow up experiments which would allow development of a cell scale mathematical model or simulation correlating short term glucose dynamics to risk of amyloid plaque formation and T2D.

The work is focused on experimental study and modelling of spacer grid influence on single- and two-phase flow. In the experimental study a mock-up of a realistic fuel bundle with five spacer grids of thin plate spring construction was investigated. A special pressure measuring technique was used to measure pressure distribution inside the spacer. Five pressure taps were drilled in one of the rods, which could exchange position with other rods, in this way providing a large degree of freedom. Laser Doppler Velocimetry was used to measure mean local axial velocity and its fluctuating component upstream and downstream of the spacer in several subchannels with differing spacer part. The experimental study revealed an interesting behaviour. Subchannels from the interior part of the bundle display a different effect on the flow downstream of the spacer compared to subchannels close to the box wall, even if the spacer part is the same. This behaviour is not reflected in modern correlations. The modelling part, first, consisted in comparing the present experimental data to Computational Fluid Dynamics calculations. It was shown that stand-alone subchannel models could predict the local velocity, but are unreliable in prediction of turbulence enhancement due to spacer. The second part of the modelling consisted in developing a deposition model for increase due to spacer. In this study Lagrangian Particle Tracking (LPT) coupled to Discrete Random Walk (DRW) technique was used to model droplet movements through turbulent flow. The LPT technique has an advantage to model the influence of turbulence structure effect on droplet deposition, in this way presenting a generalized model in view of spacer geometry change. The verification of the applicability of LPT DRW method to model deposition in annular flow at Boiling Water Reactor conditions proved that the method is unreliable in its present state. The model calculations compare reasonably well to air-water deposition data, but display a wrong trend if the fluids have a different density ratio than air-water.

Dynamic flow of material has been studied using fast neutron radiography (FNR) and positron emission particle tracking (PEPT). A new fast neutron imaging system was commissioned at The South African Nuclear Energy Corporation, Pretoria, as part of this study, although FNR measurements were ultimately performed at PhysikalischTechnische Bundesanstalt (PTB), Braunschweig. The PEPT studies were undertaken at the PEPT Cape Town facility located at iThemba LABS, Cape Town. The steady state motion of media, within a laboratory-scale tumbling mill, was studied for a range of speed and media mixes, using both FNR and PEPT. Several operational parameters were derived from the data, which could be related to potential improvements to the milling efficiency. The blending of FNR and PEPT data for the study of steady state flow, was explored for the first time. In addition, the flow of water through porous media was studied using FNR, which enabled the determination of the hydraulic conductivity, and hence intrinsic permeability, of the media within the column. The potential of using FNR, without or without PEPT, for the study of material in motion is discussed.

No description available.

The objective of this study is to compare Large-Scale Particle Image Velocimetry (LSPIV) to conventional methods for measuring discharge. Furthermore, to use the discharge data to create a rating curve at Islandsfallet in Uppsala. To measure discharge, on-site measurements have conventionally been done. Particle tracking allows flow velocimetry measurements without contact with the water. LSPIV works by measuring displacement of tracers through analysing image sequences. Using the free software Fudaa-LSPIV, flow velocity was measured and referenced to ADCP. The ADCP data were additionally used to construct the rating curve allowing to predict the water level/discharge correlation. Particle tracking was found to hold great potential in the Fyris river, and the possibility for setting up LSPIV for continuous discharge measurements should be investigated going forward. Constructing the new rating curve with discharge measurements from ADCP implied the current rating curve not being sufficient by underestimating the discharge levels necessary for a raise in water level implying the need for an updated rating curve. Concluding, does the LSPIV show promising result compared to the ADCP and the rating curve points out a big discrepancy, in higher discharge, between the new and the old rating curve. The rating curve would however need discharge data points in a greater range. / Syftet med detta arbete var att jämföra partikelspårning med mer traditionella metoder för att mäta vattenflöde. Vidare, att använda data för vattenflöde till att skapa en avbördningskurva vid Islandsfallet i Uppsala. För att mäta avrinning, är fältmätningar det konventionella sättet. Partikelspårning tillåter flödesmätningar utan krav på närvarande tekniker på plats. LSPIV fungerar genom att mäta förflyttning av spårelement på ytan genom att analysera sekvenser. Genom att använda gratisprogrammet FudaaLSPIV, mättes vattenflöde och data från ADCP användes som referensdata. Data från ADCP metoden användes också för att skapa en avbördningskurva som tillåter projicering och korrelation av vattennivå samt vattenflöde. Partikelspårning visade sig ha stor potential för Fyrisån och möjligheten att använda LSPIV för kontinuerliga mätningar bör undersökas vidare. Skapandet av den nya avbördningskurvan visade att den nuvarande avbördningskurvan underskattar vattenflödet mot vattennivån och vidare mätningar är nödvändiga för att utveckla avbördningskurvan vidare. Sammanfattningsvis visar LSPIV på positiva resultat i jämförelse med ADCP och avbördningskurvan visar på en stor diskrepans, i högre flöden, mellan den nya och den gamla avbördningskurvan. Avbördningskurvan skulle behöva ett större antal datapunkter för större flödesintervall.