Unstructured mesh - finite volume algorithms for swirling, turbulent, reacting flows

The work presented in this thesis develops techniques, employing the Finite Volume discretisation method, which allow the numerical simulation of three dimensional heat transfer and fluid flow problems using unstructured meshes. The method solves and stores all variables at the element centres which lowers storage requirements and generally shortens run times compared with the Control Volume-Finite Element approach. Correction terms are formulated which address two of the main forms of errors caused by mesh skewness. To allow a generic handling of any unstructured mesh the Cartesian components of velocity are solved under all circumstances. This leads to the requirement to adjust the discretisation of the momentum equations when there is significant flow curvature. The changes are presented in this study both when the position of the flow axis is known prior to the simulation and when its position is known only as a result of the simulation, this being the case when there is more than one source of swirling flow. These original features contribute to a Computational Fluid Dynamics code which is capable of solving swirling, turbulent fluid flow and reactive, radiative heat transfer on highly complex geometries. Specifically the techniques are applied to the simulation of processes occurring in the direct smelting of iron. The use of the Finite Volume method makes it relatively easy to employ many techniques and physical models developed for structured codes. The evaluation of the face convective fluxes is effected through the Rhie - Chow interpolation method. The SIMPLE algorithm is used in the pressure - velocity coupling. In the simulation of swirling flows it is shown that both the standard and ReNormalisation Group k-e models fail to accurately predict turbulent effects. An anisotropic hybrid (k-e and mixing length) model is developed which produces excellent numerical results for the flows of interest. The Simple Chemical Reaction Scheme is used to evaluate the transport of the various chemical species. Radiation effects are simulated through the use of the radiosity model. A series of simulation results are presented which show the capabilities of the methods in test cases ranging from simple heat transfer problems through to the simulation of two swirling jets in a three dimensional unstructured mesh

Development of self-management in pediatric inflammatory bowel disease: a qualitative exploration

Background: Self-management programs in pediatric chronic conditions, such as asthma and diabetes were effective in improving health-related outcomes. Similarly, self-management in the context of adult in inflammatory bowel disease (IBD) safely reduced healthcare costs. Nevertheless, evidence on self-management in pediatric IBD is scant. This study aims to explore self-management in pediatric IBD by exploring the childhood experience of IBD and how it is understood by the participants. Methods: Using a constructivist grounded theory approach, seven participants aged 8-17 years old were recruited in a tertiary metropolitan pediatric IBD center. Semi-structured interviews using topic guides and optional draw-and-write methods were used for data collection. Multi-level coding and constant comparison methods were utilised during data analysis. Results: The pediatric IBD self-management theory described the phenomenon of self-management through the relationship of categories that emerged from the study. Self-management starts off as a parent-dominant process that progressed to a more autonomous form with increasing disease experience. The experience was described as filled with struggles and a developing sense of control in managing these struggles. Autonomous self-management developed from the interaction of information, insight and integration. Enablers and deterrents were the contextual factors that influenced the development of self-management. Conclusions: Establishing identity both as a psychosocial developmental task and a disease-specific task is the core of self-management in childhood IBD. Future self-management programs should explore the role of structures around the child (family, school and healthcare systems) and the implementation of a proactive philosophy of involving children in managing their condition

The formation of milky way-mass disk galaxies in the first 500 million years of a cold dark matter universe

Whether or not among the myriad tiny protogalaxies there exists a population with similarities to present-day galaxies is an open question. We show, using BlueTides, the first hydrodynamic simulation large enough to resolve the relevant scales, that the first massive galaxies to form are predicted to have extensive rotationally supported disks. Although their morphology resembles in some ways Milky Way types seen at much lower redshifts, these high-redshift galaxies are smaller, denser, and richer in gas than their low-redshift counterparts. From a kinematic analysis of a statistical sample of 216 galaxies at redshift z = 8–10, we have found that disk galaxies make up 70% of the population of galaxies with stellar mass ${10}^{10}{M}_{\odot }$ or greater. Cold dark matter cosmology therefore makes specific predictions for the population of large galaxies 500 million years after the Big Bang. We argue that wide-field satellite telescopes (e.g., WFIRST) will in the near future discover these first massive disk galaxies. The simplicity of their structure and formation history should make new tests of cosmology possible

Reviews

C.S. Lewis, Poetry, and the Great War 1914-1918. John Bremer. Reviewed by Joe R. Christopher. Collected Poems. Hope Mirrlees. Ed. and intro. Sandeep Parmar. Reviewed by Nicholas Birns. Fantasy, Art and Life: Essays on George MacDonald, Robert Louis Stevenson and Other Fantasy Writers. William Gray. Reviewed by Scott McLaren. C. S. Lewis and the Middle Ages. Robert Boenig. Reviewed by Holly Ordway. Sherlock Holmes for the 21st Century: Essays on New Adaptations. Edited by Lynnette Porter. Reviewed by Janet Brennan Croft. Dancing the Tao: Le Guin and Moral Development. Sandra J. Lindow. Reviewed by Carl Badgley. Hobbit Place-names: A Linguistic Excursion Through the Shire. Rainer Nagel. Reviewed by Troels Forchhammer. The Broken Scythe: Death and Immortality in the Works of J.R.R. Tolkien. Edited by Roberto Arduini and Claudio A. Testi. Reviewed by Harley J. Sims. The Hobbit Tarot. Terry Donaldson (author of guide pamphlet) and Peter Pracownik (artist). Reviewed by Emily A Auger. The Lord of the Rings Tarot Deck and Card Game. Terry Donaldson (author of guidebook), Peter Pracownik (artist), and Mike Fitzgerald (game rules). Reviewed by Emily A Auger. J.K. Rowling: Harry Potter. Edited by Cynthia J. Hallett and Peggy J. Huey. Reviewed by Janet Brennan Croft

The BlueTides simulation: first galaxies and reionization

We introduce the BlueTides simulation and report initial results for the luminosity functions of the first galaxies and AGN, and their contribution to reionization. BlueTides was run on the BlueWaters cluster at NCSA from $z=99$ to $z=8.0$ and includes 2$\times$7040$^3$ particles in a $400$Mpc/h per side box, making it the largest hydrodynamic simulation ever performed at high redshift. BlueTides includes a pressure-entropy formulation of smoothed particle hydrodynamics, gas cooling, star formation (including molecular hydrogen), black hole growth and models for stellar and AGN feedback processes. The star formation rate density in the simulation is a good match to current observational data at $z\sim 8-10$. We find good agreement between observations and the predicted galaxy luminosity function in the currently observable range $-18\le M_{\mathrm UV} \le -22.5$ with some dust extinction required to match the abundance of brighter objects. BlueTides implements a patchy reionization model that produces a fluctuating UV background. BlueTides predicts number counts for galaxies fainter than current observational limits which are consistent with extrapolating the faint end slope of the luminosity function with a power law index $\alpha\sim -1.8$ at $z\sim 8$ and redshift dependence of $\alpha\sim (1+z)^{-0.4}$. The AGN population has a luminosity function well fit by a power law with a slope $\alpha\sim -2.4$ that compares favourably with the deepest CANDELS-Goods fields. We investigate how these luminosity functions affect the progress of reionization, and find that a high Lyman-$\alpha$ escape fraction ($f_\mathrm{esc} \sim 0.5$) is required if galaxies dominate the ionising photon budget during reionization. Smaller galaxy escape fractions imply a large contribution from faint AGN (down to $M_\mathrm{UV}=-12$) which results in a rapid reionization, disfavoured by current observations