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Chaotic Advection in ThreeDimensional Unsteady Incompressible Laminar Flow
, 1996
"... this paper we take advantage of the spherical symmetry of the geometry of this system to y Email julyan@hp1.uib.es, Web http://formentor.uib.es/julyan. ..."
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this paper we take advantage of the spherical symmetry of the geometry of this system to y Email julyan@hp1.uib.es, Web http://formentor.uib.es/julyan.
Stochastic geometry of polygonal networks  an alternative approach to the hexagonsquaretransition in Bénard convection
, 1997
"... The tools of stochastic geometry are applied to the transition from hexagonal to square cells recently observed in surfacetensiondriven Benard convection. By means of this method we study the metrical and topological evolution of Benard cells as a function of the temperature di#erence across the l ..."
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The tools of stochastic geometry are applied to the transition from hexagonal to square cells recently observed in surfacetensiondriven Benard convection. By means of this method we study the metrical and topological evolution of Benard cells as a function of the temperature di#erence across the layer. We find distinct di#erences in the metric of the three cell types. While sidelength, area and perimeter of hexagons and squares grow monotoneously, the particular quantities of the pentagons change with onset of the transition in a steplike manner. Below the transition the pentagons behave similiar to hexagons, above close to squares which underlines their mediating character within the transition. The relation between perimeter and area plays obviously a decisive role for the stability of one cell class. We show that the perimeterarea ratio of a square Benard cell exceeds that of the hexagonal one by an unexpected high value. We find that the Benard pattern obeys to the AboavWeair...
Simulation of ThreeDimensional BénardMarangoni Flows Including Deformed Surfaces
, 2009
"... We present a coupled thermalfluid model for BénardMarangoni convection in a threedimensional fluid layer. The governing equations are derived in detail for two reasons: first, we do not assume a flat free surface as commonly done; and second, we prepare for the use of flexible discretizations. Th ..."
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We present a coupled thermalfluid model for BénardMarangoni convection in a threedimensional fluid layer. The governing equations are derived in detail for two reasons: first, we do not assume a flat free surface as commonly done; and second, we prepare for the use of flexible discretizations. The governing equations are discretized using spectral elements in space and an operator splitting approach in time. Since we are here primarily interested in steady state solutions, the focus is on the spatial discretization. The overall computational approach is very attractive to use for several reasons: (i) the solution can be expected to have a high degree of regularity, and rapid convergence can be expected; (ii) the spectral element decomposition automatically gives a convenient parameterization of the free surface that allows powerful results from differential geometry to easily be exploited; (iii) free surface deformation can readily be included; (iv) both normal and tangential stresses are conveniently accounted for through a single surface integral; (v) no differentiation of the surface tension is necessary in order to include thermocapillary effects (due to integrationbyparts twice); (vi) the geometry representation of the free surface need only be C 0 across element boundaries even though curvature effects are included. Threedimensional simulation results are presented, including the free surface deflection due to buoyancy and thermocapillary effects.
Understanding Complex Adaptive Systems by Playing Games
, 2009
"... Abstract. While educators teach their students about decision making in complex environments, managers have to deal with the complexity of large projects on a daily basis. To make better decisions it is assumed, that the latter would benefit from better understanding of complex phenomena, as do stu ..."
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Abstract. While educators teach their students about decision making in complex environments, managers have to deal with the complexity of large projects on a daily basis. To make better decisions it is assumed, that the latter would benefit from better understanding of complex phenomena, as do students as the professionals of the future. The goal of this article is to evaluate the relevance of the use of simulation games for learning about the complexity of largescale sociotechnical projects. Relevant concepts from complex adaptive systems will be introduced or described. The conjecture is that complex adaptive systems can be simulated by games, in which players are able to experience the system workings, and retrieve more insight in their complex behaviour as a result. The multiplayer computer game SimPortMV2 illustrates this by simulating the decision making process revolving around Maasvlakte 2 (MV2), an extension of the Port of Rotterdam into the North Sea. The game has been played by hundreds of students of higher education. Based on this study, we present preliminary indications of learning and conclusions on how simulation games can provide insights in a complex adaptive system and be used to educate both students and professionals.
Two Dimensional DSMC Calculations of the Rayleigh Bénard Instability
, 1996
"... : The Rayleigh B'enard instability is a well known phenomena in which a fluid layer confined between two horizontal, parallel plates heated from below spontaneously initiates convection at some critical temperature difference between the plates. The convective motion takes the form of parallel ..."
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: The Rayleigh B'enard instability is a well known phenomena in which a fluid layer confined between two horizontal, parallel plates heated from below spontaneously initiates convection at some critical temperature difference between the plates. The convective motion takes the form of parallel fluid rolls. A layer of rarefied Helium gas at cryogenic temperatures confined between two plates is simulated in two dimensions by means of the direct simulation Monte Carlo (DSMC) method. The transition from a stable layer to large scale convective motion is simulated. At higher temperature differences some experimentally verified nonlinear phenomena are also observed. The use of the nondimensional heat flux incident on the upper plate is recommended for use when comparing further DSMC studies, as in experiments. Suggestions for further work are also made. 1 INTRODUCTION If a fluid is confined between two horizontal, parallel, perfectly conducting plates and the bottom plate is heated, such...
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"... In this paper, we propose a new model for coherent clustering of gene expression data called regcluster. The proposed model allows (1) the expression profiles of genes in a cluster to follow any shiftingandscaling patterns in subspace, where the scaling can be either positive or negative, and (2) ..."
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In this paper, we propose a new model for coherent clustering of gene expression data called regcluster. The proposed model allows (1) the expression profiles of genes in a cluster to follow any shiftingandscaling patterns in subspace, where the scaling can be either positive or negative, and (2) the expression value changes across any two conditions of the cluster to be significant. No previous work measures up to the task that we have set: the densitybased subspace clustering algorithms require genes to have similar expression levels to each other in subspace; the patternbased biclustering algorithmsonlyallowpureshiftingorpurescalingpatterns; and the tendencybased biclustering algorithms have no coherence guarantees. We also develop a novel patternbased biclustering algorithm for identifying shiftingandscaling coregulation patterns, satisfying both coherence constraint and regulation constraint. Our experimental results show that the regcluster algorithm is able to detect a significant amount of clusters missed by previous models, and these clusters are potentially of high biological significance. 1.
Revisiting the 1954 suspension experiments of R. A. Bagnold
, 2002
"... In 1954 R. A. Bagnold published his seminal findings on the rheological properties of a liquidsolid suspension. Although this work has been cited extensively over the last fifty years, there has not been a critical review of the experiments. The purpose of this study is to examine the work and to s ..."
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In 1954 R. A. Bagnold published his seminal findings on the rheological properties of a liquidsolid suspension. Although this work has been cited extensively over the last fifty years, there has not been a critical review of the experiments. The purpose of this study is to examine the work and to suggest an alternative reason for the experimental ndings. The concentric cylinder rheometer was designed to measure simultaneously the shear and normal forces for a wide range of solid concentrations, fluid viscosities and shear rates. As presented by Bagnold, the analysis and experiments demonstrated that the shear and normal forces depended linearly on the shear rate in the ‘macroviscous’ regime; as the graintograin interactions increased in the ‘graininertia’ regime, the stresses depended on the square of the shear rate and were independent of the fluid viscosity. These results, however, appear to be dictated by the design of the experimental facility. In Bagnold’s experiments, the height (h) of the rheometer was relatively short compared to the spacing (t) between the rotating outer and stationary inner cylinder (h=t = 4:6). Since the top and bottom end plates rotated with the outer cylinder, the flow contained two axisymmetric counterrotating cells in which
LIQUIDLIQUID EXTRACTION BASED ON A NEW FLOW PATTERN: TWOFLUID TAYLORCOUETTE FLOW
, 1999
"... at the Universityof WisconsinMadison The exploitation of flow instabilities that can occur in rotating flows is investigated as a new approach to liquidliquid extraction. Two immiscible liquids are radially stratified by centrifugal force in the annulus between corotating coaxial cylinders. When ..."
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at the Universityof WisconsinMadison The exploitation of flow instabilities that can occur in rotating flows is investigated as a new approach to liquidliquid extraction. Two immiscible liquids are radially stratified by centrifugal force in the annulus between corotating coaxial cylinders. When the inner cylinder is then rotated above a critical speed, Taylor vortices form in one or both of the fluids. Although the flow pattern yields a relatively small amount of interfacial surface area, the surface is highly active for interphase mass transfer due to the local vortex motion. With the addition i of countercurrent axial flow, efficient continuous processing is also possible. It is proposed that this twofluid TaylorCouette flow yields a viable extraction process, particularly for fluid pairs that are easily emulsifiable and therefore have limited processing options with the current commercially available equipment. With this goal, the present study of twofluid TaylorCouette flow with coun
Longwave Marangoni instability with vibration
 J. Fluid Mech
"... The effect of vertical vibration on the longwave instability of a Marangoni system is studied. The vibration augments the stabilizing effect of surface tension in bounded systems. In laterally unbounded systems nonlinear terms can stabilize nonflat states and prevent the appearance of dry spots. T ..."
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The effect of vertical vibration on the longwave instability of a Marangoni system is studied. The vibration augments the stabilizing effect of surface tension in bounded systems. In laterally unbounded systems nonlinear terms can stabilize nonflat states and prevent the appearance of dry spots. The effect of a slight inclination of the system is also considered. 1.