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Stephen W. Morris

Bio: Stephen W. Morris is an academic researcher from University of Toronto. The author has contributed to research in topics: Buoyancy & Vortex. The author has an hindex of 27, co-authored 68 publications receiving 1990 citations. Previous affiliations of Stephen W. Morris include University of British Columbia & University of California, Santa Barbara.


Papers
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Journal ArticleDOI
TL;DR: The correlation length of the pattern decreased rapidly with increasing control parameter so that the size of a correlated area became much smaller than the area of the cell, suggesting that the chaotic behavior is intrinsic to large aspect ratio geometries.
Abstract: We report experiments on convection patterns in a cylindrical cell with a large aspect ratio. The fluid had a Prandtl number [sigma][approx]1. We observed a chaotic pattern consisting of many rotating spirals and other defects in the parameter range where theory predicts that steady straight rolls should be stable. The correlation length of the pattern decreased rapidly with increasing control parameter so that the size of a correlated area became much smaller than the area of the cell. This suggests that the chaotic behavior is intrinsic to large aspect ratio geometries.

222 citations

Journal ArticleDOI
TL;DR: There is some evidence of a gradual increase in disorder as the drying layer become thinner, but no sudden transition, in contrast to what has been seen in previous experiments.
Abstract: We have studied shrinkage-crack patterns which form when a thin layer of an alumina/water slurry dries. Both isotropic and directional drying were studied. The dynamics of the pattern formation process and the geometric properties of the isotropic crack patterns are similar to what is expected from recent models, assuming weak disorder. There is some evidence of a gradual increase in disorder as the drying layer become thinner, but no sudden transition, in contrast to what has been seen in previous experiments. The morphology of the crack patterns is influenced by drying gradients and front propagation effects, with sharp gradients having a strong orienting and ordering effect.

192 citations

Journal ArticleDOI
TL;DR: In this article, the authors review the history of experimental work on Rayleigh-Benard convection in gases, and then describe a modern apparatus that has been used in their experiments on gas convection.
Abstract: We review the history of experimental work on Rayleigh–Benard convection in gases, and then describe a modern apparatus that has been used in our experiments on gas convection. This system allows for the study of patterns in a cell with an aspect ratio (cell radius/fluid layer depth) as large as 100, with the cell thickness uniform to a fraction of a μm, and with the pressure controlled at the level of one part in 105. This level of control can yield a stability of the critical temperature difference for the convective onset of better than one part in 104. The convection patterns are visualized and the temperature field can be inferred using the shadowgraph technique. We describe the flow visualization and image processing necessary for this. Some interesting results obtained with the system are briefly summarized.

118 citations

Journal ArticleDOI
TL;DR: Measurements of the crack spacing from both laboratory and geological investigations of columnar jointing are presented, and it is shown how these data can be collapsed onto a single master scaling curve.
Abstract: Crack patterns in laboratory experiments on thick samples of drying cornstarch are geometrically similar to columnar joints in cooling lava found at geological sites such as the Giant's Causeway. We present measurements of the crack spacing from both laboratory and geological investigations of columnar jointing, and show how these data can be collapsed onto a single master scaling curve. This is due to the underlying mathematical similarity between theories for the cracking of solids induced by differential drying or by cooling. We use this theory to give a simple quantitative explanation of how these geometrically similar crack patterns arise from a single dynamical law rooted in the nonequilibrium nature of the phenomena. We also give scaling relations for the characteristic crack spacing in other limits consistent with our experiments and observations, and discuss the implications of our results for the control of crack patterns in thin and thick solid films.

105 citations

Journal ArticleDOI
TL;DR: In this paper, the scaling relationship between column width and the size of the striae and relate these quantitatively to thermal and fracture models was examined in detail, showing that column radius and stria size are proportional to each other and inversely proportional to the cooling rate of the lava.
Abstract: [1] We describe field work, analysis, and modeling of columnar joints from the Columbia River Basalt Group. This work is focused on the regions around the Grand Coulee, Snake River, and Columbia Gorge, which form parts of this unusually homogeneous and very large sample of columnar basalt. We examine in detail the scaling relationship between the column width and the size of the striae and relate these quantitatively to thermal and fracture models. We found that the column radius and stria size are proportional to each other and inversely proportional to the cooling rate of the lava. Near a flow margin, our results put observational constraints on diffusive thermal models of joint formation. Deeper than a few meters into a colonnade, our measurements are consistent with a simple advection-diffusion model of two-phase convective cooling within the joints, regardless of the direction of cooling. This model allows an accurate comparison of igneous columnar jointing and joints due to desiccation in laboratory analog systems. We also identify a new length scale in which wavy columns can appear in some colonnades. The mechanisms leading to the wavy columns are likely related to those underlying similar wavy cracks in 2-D analog systems.

100 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, the Nusselt number and the Reynolds number depend on the Rayleigh number Ra and the Prandtl number Pr, and the thicknesses of the thermal and the kinetic boundary layers scale with Ra and Pr.
Abstract: The progress in our understanding of several aspects of turbulent Rayleigh-Benard convection is reviewed. The focus is on the question of how the Nusselt number and the Reynolds number depend on the Rayleigh number Ra and the Prandtl number Pr, and on how the thicknesses of the thermal and the kinetic boundary layers scale with Ra and Pr. Non-Oberbeck-Boussinesq effects and the dynamics of the large scale convection roll are addressed as well. The review ends with a list of challenges for future research on the turbulent Rayleigh-Benard system.

1,372 citations

Journal ArticleDOI
TL;DR: In this article, a review summarizes results for Rayleigh-Benard convection that have been obtained over the past decade or so, focusing on convection in compressed gases and gas mixtures with Prandtl numbers near one and smaller.
Abstract: ▪ Abstract This review summarizes results for Rayleigh-Benard convection that have been obtained over the past decade or so. It concentrates on convection in compressed gases and gas mixtures with Prandtl numbers near one and smaller. In addition to the classical problem of a horizontal stationary fluid layer heated from below, it also briefly covers convection in such a layer with rotation about a vertical axis, with inclination, and with modulation of the vertical acceleration.

823 citations

Book
18 Oct 2001
TL;DR: In this paper, Ball explains why these are not coincidences Nature commonly weaves its tapestry without any master plan or blueprint Instead, these designs build themselves by self-organization The interactions between the component parts give rise to spontaneous patterns that are at the same time complex and beautiful Many of these patterns are universal, recurring again and again in the natural order: spirals, spots, stripes, branches, honeycombs Philip Ball conducts a profusely illustrated tour of this gallery, and reveals the secrets of how nature's patterns are made.
Abstract: From the Publisher: Why do similar patterns and forms appear in nature in settings that seem to bear no relation to one another? The Windblown ripples of desert sand follow a sinuous course that resembles the stripes of a zebra or a marine fish In the trellis-like shells of microscopic sea creatures we see the same geometry as in the bubble walls of foam, Forks of lightning mirror the branches of a river network or a tree This book explains why these are not coincidences Nature commonly weaves its tapestry without any master plan or blueprint Instead, these designs build themselves by self-organization The interactions between the component parts -- whether they be grains of sand, molecules or living cells -- give rise to spontaneous patterns that are at the same time complex and beautiful Many of these patterns are universal, recurring again and again in the natural order: spirals, spots, stripes, branches, honeycombs Philip Ball conducts a profusely illustrated tour of this gallery, and reveals the secrets of how nature's patterns are made

700 citations

Journal ArticleDOI
TL;DR: In this paper, the authors survey a number of situations in which nontrivial patterns emerge in granular systems, elucidates important distinctions between these phenomena and similar ones occurring in continuum fluids, and describes general principles and models of pattern formation in complex systems that have been successfully applied to granular system.
Abstract: Granular materials are ubiquitous in our daily lives. While they have been the subject of intensive engineering research for centuries, in the last two decades granular matter has attracted significant attention from physicists. Yet despite major efforts by many groups, the theoretical description of granular systems remains largely a plethora of different, often contradictory concepts and approaches. Various theoretical models have emerged for describing the onset of collective behavior and pattern formation in granular matter. This review surveys a number of situations in which nontrivial patterns emerge in granular systems, elucidates important distinctions between these phenomena and similar ones occurring in continuum fluids, and describes general principles and models of pattern formation in complex systems that have been successfully applied to granular systems.

667 citations