Magneto-hydrodynamical model for plasma
Liu, Ruikuan; Yang, Jiayan
2017-10-01
Based on the Newton's second law and the Maxwell equations for the electromagnetic field, we establish a new 3-D incompressible magneto-hydrodynamics model for the motion of plasma under the standard Coulomb gauge. By using the Galerkin method, we prove the existence of a global weak solution for this new 3-D model.
The stochastic tetrad magneto-hydrodynamics via functional formalism
Materassi, Massimo; Consolini, Giuseppe
2015-12-01
> In this work we discuss an application of the Tetrad Dynamics approach, a stochastic dynamical theory already introduced in hydrodynamic turbulence, to incompressible magneto-hydrodynamics. This theoretical framework is capable of taking into account some crucial aspects of turbulent plasmas, namely, (i) its material nature, which is stressed through the adoption of Lagrangian variables, (ii) its probabilistic dynamics, which is fundamental to understand the intermittency and highly irregular nature of turbulence, and (iii) the multi-scale character of interactions, which is approached by promoting the space size of parcels to the role of a dynamical variable. In particular, here, we construct the probabilistic equations of motion for quantities describing the evolution of a turbulent plasma (a matrix describing the parcel's shape, the plasma velocity and magnetic field coarse-grained gradient tensors, and ), resorting the functional formalism of classical statistical dynamics. Through the introduction of a stochastic action and using a path integral approach, the statistical properties of can be derived from those of noises appearing in their equations of motion, both at equilibrium and out of equilibrium.
Viscosity and Vorticity in Reduced Magneto-Hydrodynamics
Energy Technology Data Exchange (ETDEWEB)
Joseph, Ilon [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2015-08-12
Magneto-hydrodynamics (MHD) critically relies on viscous forces in order for an accurate determination of the electric eld. For each charged particle species, the Braginskii viscous tensor for a magnetized plasma has the decomposition into matrices with special symmetries.
Active control of magneto-hydrodynamic instabilities in hot plasmas
Energy Technology Data Exchange (ETDEWEB)
Igochine, Valentin (ed.) [Max-Planck-Institut fuer Plasmaphysik, Garching (Germany)
2015-04-01
Written and edited by leading plasma physics researchers. Provides a toolkit for scientists and engineers aiming to optimize plasma performance. Comprehensive treatment of different plasma instabilities. During the past century, world-wide energy consumption has risen dramatically, which leads to a quest for new energy sources. Fusion of hydrogen atoms in hot plasmas is an attractive approach to solve the energy problem, with abundant fuel, inherent safety and no long-lived radioactivity. However, one of the limits on plasma performance is due to the various classes of magneto-hydrodynamic instabilities that may occur. The physics and control of these instabilities in modern magnetic confinement fusion devices is the subject of this book. Written by foremost experts, the contributions will provide valuable reference and up-to-date research reviews for ''old hands'' and newcomers alike.
Active control of magneto-hydrodynamic instabilities in hot plasmas
2015-01-01
During the past century, world-wide energy consumption has risen dramatically, which leads to a quest for new energy sources. Fusion of hydrogen atoms in hot plasmas is an attractive approach to solve the energy problem, with abundant fuel, inherent safety and no long-lived radioactivity. However, one of the limits on plasma performance is due to the various classes of magneto-hydrodynamic instabilities that may occur. The physics and control of these instabilities in modern magnetic confinement fusion devices is the subject of this book. Written by foremost experts, the contributions will provide valuable reference and up-to-date research reviews for "old hands" and newcomers alike.
A Tightly Coupled Non-Equilibrium Magneto-Hydrodynamic Model for Inductively Coupled RF Plasmas
2016-02-29
Journal Article 3. DATES COVERED (From - To) 12 May 2015 – 06 Oct 2015 4. TITLE AND SUBTITLE A Tightly Coupled Non-Equilibrium Magneto- Hydrodynamic ...development a tightly coupled magneto- hydrodynamic model for Inductively Coupled Radio- Frequency (RF) Plasmas. Non Local Thermodynamic Equilibrium (NLTE... hydrodynamic model for Inductively Coupled RF Plasmas A. Munafò,1, a) S. A. Alfuhaid,1, b) J.-L. Cambier,2, c) and M. Panesi1, d) 1)Department of
Numerical magneto-hydrodynamics for relativistic nuclear collisions
Energy Technology Data Exchange (ETDEWEB)
Inghirami, Gabriele [Frankfurt Institute for Advanced Studies, Frankfurt am Main (Germany); Goethe-Universitaet, Institute for Theoretical Physics, Frankfurt am Main (Germany); GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, Darmstadt (Germany); Forschungszentrum Juelich, John von Neumann Institute for Computing, Juelich (Germany); Del Zanna, Luca [Universita di Firenze, Dipartimento di Fisica e Astronomia, Firenze (Italy); INAF - Osservatorio Astrofisico di Arcetri, Firenze (Italy); INFN - Sezione di Firenze, Firenze (Italy); Beraudo, Andrea [INFN - Sezione di Torino, Torino (Italy); Moghaddam, Mohsen Haddadi [INFN - Sezione di Torino, Torino (Italy); Hakim Sabzevari University, Department of Physics, P. O. Box 397, Sabzevar (Iran, Islamic Republic of); Becattini, Francesco [Universita di Firenze, Dipartimento di Fisica e Astronomia, Firenze (Italy); INFN - Sezione di Firenze, Firenze (Italy); Bleicher, Marcus [Frankfurt Institute for Advanced Studies, Frankfurt am Main (Germany); Goethe-Universitaet, Institute for Theoretical Physics, Frankfurt am Main (Germany); GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, Darmstadt (Germany); Forschungszentrum Juelich, John von Neumann Institute for Computing, Juelich (Germany)
2016-12-15
We present an improved version of the ECHO-QGP numerical code, which self-consistently includes for the first time the effects of electromagnetic fields within the framework of relativistic magneto-hydrodynamics (RMHD). We discuss results of its application in relativistic heavy-ion collisions in the limit of infinite electrical conductivity of the plasma. After reviewing the relevant covariant 3 + 1 formalisms, we illustrate the implementation of the evolution equations in the code and show the results of several tests aimed at assessing the accuracy and robustness of the implementation. After providing some estimates of the magnetic fields arising in non-central high-energy nuclear collisions, we perform full RMHD simulations of the evolution of the quark-gluon plasma in the presence of electromagnetic fields and discuss the results. In our ideal RMHD setup we find that the magnetic field developing in non-central collisions does not significantly modify the elliptic flow of the final hadrons. However, since there are uncertainties in the description of the pre-equilibrium phase and also in the properties of the medium, a more extensive survey of the possible initial conditions as well as the inclusion of dissipative effects are indeed necessary to validate this preliminary result. (orig.)
Friedrich, J; Schäfer, T; Grauer, R
2016-01-01
We investigate the scaling behavior of longitudinal and transverse structure functions in homogeneous and isotropic magneto-hydrodynamic (MHD) turbulence by means of an exact hierarchy of structure function equations as well as by direct numerical simulations of two- and three-dimensional MHD turbulence. In particular, rescaling relations between longitudinal and transverse structure functions are derived and utilized in order to compare different scaling behavior in the inertial range. It is found that there are no substantial differences between longitudinal and transverse structure functions in MHD turbulence. This finding stands in contrast to the case of hydrodynamic turbulence which shows persistent differences even at high Reynolds numbers. We propose a physical picture that is based on an effective reduction of pressure contributions due to local regions of same magnitude and alignment of velocity and magnetic field fluctuations. Finally, our findings underline the importance of the pressure term for ...
Development and validation of a magneto-hydrodynamic solver for blood flow analysis
Energy Technology Data Exchange (ETDEWEB)
Kainz, W; Guag, J; Krauthamer, V; Myklebust, J; Bassen, H; Chang, I [Center for Devices and Radiological Health, FDA, Silver Spring, MD (United States); Benkler, S; Chavannes, N [Schmid and Partner Engineering AG, Zurich (Switzerland); Szczerba, D; Neufeld, E; Kuster, N [Foundation for Research on Information Technology in Society (IT' IS), Zurich (Switzerland); Kim, J H; Sarntinoranont, M, E-mail: wolfgang.kainz@fda.hhs.go [Soft Tissue Mechanics and Drug Delivery Laboratory, Mechanical and Aerospace Engineering, University of Florida, FL (United States)
2010-12-07
The objective of this study was to develop a numerical solver to calculate the magneto-hydrodynamic (MHD) signal produced by a moving conductive liquid, i.e. blood flow in the great vessels of the heart, in a static magnetic field. We believe that this MHD signal is able to non-invasively characterize cardiac blood flow in order to supplement the present non-invasive techniques for the assessment of heart failure conditions. The MHD signal can be recorded on the electrocardiogram (ECG) while the subject is exposed to a strong static magnetic field. The MHD signal can only be measured indirectly as a combination of the heart's electrical signal and the MHD signal. The MHD signal itself is caused by induced electrical currents in the blood due to the moving of the blood in the magnetic field. To characterize and eventually optimize MHD measurements, we developed a MHD solver based on a finite element code. This code was validated against literature, experimental and analytical data. The validation of the MHD solver shows good agreement with all three reference values. Future studies will include the calculation of the MHD signals for anatomical models. We will vary the orientation of the static magnetic field to determine an optimized location for the measurement of the MHD blood flow signal.
Kumar, Vikash; Rezai, Pouya
2017-06-01
Sorting cells, microorganisms and particles from a solution is of paramount importance in many biological applications. An ideal sorting device should work at high throughput, involve simple design, avoid energy consumption, operate without a diluting sheath flow and perform separation with high purity. However, currently available sorting methods such as pinched flow fractionation, hydrodynamic filtration, magnetophoresis and deterministic lateral displacement meet only a few of the above-mentioned characteristics. In this paper, we report a hybrid technique combining magnetic focusing of particles in a thin microchannel and their hydrodynamic fractionation at a downstream expansion region, to devise a sheathless and high-throughput Magneto-Hydrodynamic Fractionation (MHF) method. First, sheathless magnetic focusing of 11 μm microparticles against the wall of the thin microchannel was investigated over a wide range of flow rates (0.5-5 mL h-1). Then, a mixture of 5 μm and 11 μm paramagnetic particles was injected into the device at a flow rate of 5 mL h-1 to demonstrate their sorting. Both of these magnetic particles were aligned along the wall of the channel and hence focused in the device, however their centers were lying on different streamlines due to their different sizes. Therefore, they were separated into distinct streamlines upon entering into the expansion region. Using this device, we achieved a high throughput sorting of more than 104 particles per second with an approximate on-chip fractionation purity of 98%. This technique has a great potential for separation of more than two magnetic particles for application in immunomagnetic affinity-based sorting of multiple biological substances.
Hayat, Tasawar; Awais, Muhammad; Imtiaz, Amna
2016-01-01
This communication deals with the properties of heat source/sink in a magneto-hydrodynamic flow of a non-Newtonian fluid immersed in a porous medium. Shrinking phenomenon along with the permeability of the wall is considered. Mathematical modelling is performed to convert the considered physical process into set of coupled nonlinear mathematical equations. Suitable transformations are invoked to convert the set of partial differential equations into nonlinear ordinary differential equations which are tackled numerically for the solution computations. It is noted that dual solutions for various physical parameters exist which are analyzed in detail.
Panta, Yogendra M.; Qian, Shizhi; Cheney, Marcos A.
2007-11-01
We experimentally investigated the effects of magnetic fields on the anodic currents in the determination of mercury (II) ions in aqueous solutions with the linear sweep stripping voltammetry technique. In the stripping analysis, a potential difference is applied across the working and reference electrodes positioned in the working sample, then a transmitted current density through the sample results. When the electrochemical cell is placed on a permanent magnet, a magneto-hydrodynamic (MHD) convection is induced through the interaction between the current density and the magnetic field. The induced MHD convection enhances the ionic mass transport of the Hg^2+ ions during both the deposition and stripping steps without the use of any mechanical stirrers or rotating electrodes. This leads to a larger anodic current, thus obtaining higher detection sensitivity for the determination of mercury (II) ions.
Simulation of two-dimensional fully developed laminar flow for a magneto-hydrodynamic (MHD) pump.
Wang, Pei-Jen; Chang, Chia-Yuan; Chang, Ming-Lang
2004-07-30
MHD micro-pumps circumvent the wear and fatigue caused by high pressure-drop across the check valves of mechanical micro-pumps in micro-fluidic systems. Early analyses of the fluid flow for MHD micro-pumps were mostly made possible by the Poiseuille flow theory; however, this conventional laminar approach cannot illustrate the effects of various channel sizes and shapes. This paper, therefore, presents a simplified MHD flow model based upon steady state, incompressible and fully developed laminar flow theory to investigate the characteristics of a MHD pump. Inside the pump, flowing along the channel is the electrically conducting fluid flowing driven by the Lorentz forces in the direction perpendicular to both dc magnetic field and applied electric currents. The Lorentz forces were converted into a hydrostatic pressure gradient in the momentum equations of the MHD channel flow model. The numerical simulations conducted with the explicit finite difference method show that the channel dimensions and the induced Lorentz forces have significant influences on the flow velocity profile. Furthermore, the simulation results agree well with the experimental results published by other researchers.
Mirza, I A; Abdulhameed, M; Vieru, D; Shafie, S
2016-12-01
Therapies with magnetic/electromagnetic field are employed to relieve pains or, to accelerate flow of blood-particles, particularly during the surgery. In this paper, a theoretical study of the blood flow along with particles suspension through capillary was made by the electro-magneto-hydrodynamic approach. Analytical solutions to the non-dimensional blood velocity and non-dimensional particles velocity are obtained by means of the Laplace transform with respect to the time variable and the finite Hankel transform with respect to the radial coordinate. The study of thermally transfer characteristics is based on the energy equation for two-phase thermal transport of blood and particles suspension with viscous dissipation, the volumetric heat generation due to Joule heating effect and electromagnetic couple effect. The solution of the nonlinear heat transfer problem is derived by using the velocity field and the integral transform method. The influence of dimensionless system parameters like the electrokinetic width, the Hartman number, Prandtl number, the coefficient of heat generation due to Joule heating and Eckert number on the velocity and temperature fields was studied using the Mathcad software. Results are presented by graphical illustrations. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.
Abdulhameed, M.; Vieru, D.; Roslan, R.
2017-10-01
This paper investigates the electro-magneto-hydrodynamic flow of the non-Newtonian behavior of biofluids, with heat transfer, through a cylindrical microchannel. The fluid is acted by an arbitrary time-dependent pressure gradient, an external electric field and an external magnetic field. The governing equations are considered as fractional partial differential equations based on the Caputo-Fabrizio time-fractional derivatives without singular kernel. The usefulness of fractional calculus to study fluid flows or heat and mass transfer phenomena was proven. Several experimental measurements led to conclusion that, in such problems, the models described by fractional differential equations are more suitable. The most common time-fractional derivative used in Continuum Mechanics is Caputo derivative. However, two disadvantages appear when this derivative is used. First, the definition kernel is a singular function and, secondly, the analytical expressions of the problem solutions are expressed by generalized functions (Mittag-Leffler, Lorenzo-Hartley, Robotnov, etc.) which, generally, are not adequate to numerical calculations. The new time-fractional derivative Caputo-Fabrizio, without singular kernel, is more suitable to solve various theoretical and practical problems which involve fractional differential equations. Using the Caputo-Fabrizio derivative, calculations are simpler and, the obtained solutions are expressed by elementary functions. Analytical solutions of the biofluid velocity and thermal transport are obtained by means of the Laplace and finite Hankel transforms. The influence of the fractional parameter, Eckert number and Joule heating parameter on the biofluid velocity and thermal transport are numerically analyzed and graphic presented. This fact can be an important in Biochip technology, thus making it possible to use this analysis technique extremely effective to control bioliquid samples of nanovolumes in microfluidic devices used for biological
Magneto-hydrodynamics Simulation in Astrophysics
Pang, Bijia
2011-08-01
Magnetohydrodynamics (MHD) studies the dynamics of an electrically conducting fluid under the influence of a magnetic field. Many astrophysical phenomena are related to MHD, and computer simulations are used to model these dynamics. In this thesis, we conduct MHD simulations of non-radiative black hole accretion as well as fast magnetic reconnection. By performing large scale three dimensional parallel MHD simulations on supercomputers and using a deformed-mesh algorithm, we were able to conduct very high dynamical range simulations of black hole accretion of Sgr A* at the Galactic Center. We find a generic set of solutions, and make specific predictions for currently feasible observations of rotation measure (RM). The magnetized accretion flow is subsonic and lacks outward convection flux, making the accretion rate very small and having a density slope of around -1. There is no tendency for the flows to become rotationally supported, and the slow time variability of th! e RM is a key quantitative signature of this accretion flow. We also provide a constructive numerical example of fast magnetic reconnection in a three-dimensional periodic box. Reconnection is initiated by a strong, localized perturbation to the field lines and the solution is intrinsically three-dimensional. Approximately 30% of the magnetic energy is released in an event which lasts about one Alfvén time, but only after a delay during which the field lines evolve into a critical configuration. In the co-moving frame of the reconnection regions, reconnection occurs through an X-like point, analogous to the Petschek reconnection. The dynamics appear to be driven by global flows rather than local processes. In addition to issues pertaining to physics, we present results on the acceleration of MHD simulations using heterogeneous computing systems te{shan2006heterogeneous}. We have implemented the MHD code on a variety of heterogeneous and multi-core architectures (multi-core x86, Cell, Nvidia and ATI GPU) using different languages (FORTRAN, C, Cell, CUDA and OpenCL). Initial performance results for these systems are presented, and we conclude that substantial gains in performance over traditional systems are possible. In particular, it is possible to extract a greater percentage of peak theoretical performance from some heterogeneous systems when compared to x86 architectures.
Computation of Viscous Incompressible Flows
Kwak, Dochan
2011-01-01
This monograph is intended as a concise and self-contained guide to practitioners and graduate students for applying approaches in computational fluid dynamics (CFD) to real-world problems that require a quantification of viscous incompressible flows. In various projects related to NASA missions, the authors have gained CFD expertise over many years by developing and utilizing tools especially related to viscous incompressible flows. They are looking at CFD from an engineering perspective, which is especially useful when working on real-world applications. From that point of view, CFD requires two major elements, namely methods/algorithm and engineering/physical modeling. As for the methods, CFD research has been performed with great successes. In terms of modeling/simulation, mission applications require a deeper understanding of CFD and flow physics, which has only been debated in technical conferences and to a limited scope. This monograph fills the gap by offering in-depth examples for students and engine...
Computational fluid dynamics incompressible turbulent flows
Kajishima, Takeo
2017-01-01
This textbook presents numerical solution techniques for incompressible turbulent flows that occur in a variety of scientific and engineering settings including aerodynamics of ground-based vehicles and low-speed aircraft, fluid flows in energy systems, atmospheric flows, and biological flows. This book encompasses fluid mechanics, partial differential equations, numerical methods, and turbulence models, and emphasizes the foundation on how the governing partial differential equations for incompressible fluid flow can be solved numerically in an accurate and efficient manner. Extensive discussions on incompressible flow solvers and turbulence modeling are also offered. This text is an ideal instructional resource and reference for students, research scientists, and professional engineers interested in analyzing fluid flows using numerical simulations for fundamental research and industrial applications. • Introduces CFD techniques for incompressible flow and turbulence with a comprehensive approach; • Enr...
Successes and Challenges of Incompressible Flow Simulation
Kwak, Dochan; Kiris, Cetin
2003-01-01
During the past thirty years, numerical methods and simulation tools for incompressible flows have been advanced as a subset of CFD discipline. Even though incompressible flows are encountered in many areas of engineering, simulation of compressible flow has been the major driver for developing computational algorithms and tools. This is probably due to rather stringent requirements for predicting aerodynamic performance characteristics of flight vehicles, while flow devices involving low speed or incompressible flow could be reasonably well designed without resorting to accurate numerical simulations. As flow devices are required to be more sophisticated and highly efficient, CFD tools become indispensable in fluid engineering for incompressible and low speed flow. This paper is intended to review some of the successes made possible by advances in computational technologies during the same period, and discuss some of the current challenges.
Unsteady Magneto-Hydrodynamic (MHD) flow of a uniformly ...
African Journals Online (AJOL)
Numerical results are presented for the transient and steady state Velocity, Temperature and Concentration fields. These results are obtained by solving the partial differential equations describing the conservation, momentum energy and species concentration by an explicit finite – difference method in time – dependent ...
Compression modes and the nuclear matter incompressibility ...
Indian Academy of Sciences (India)
We review the current status of the nuclear matter ( = and no Coulomb interaction) incompressibility coefﬁcient, , and describe the theoretical and the experimental methods used to determine from properties of compression modes in nuclei. In particular we consider the long standing problem of the conﬂicting ...
Viscoelastic Models for Nearly Incompressible Materials
2009-09-01
outlined first, then the Prony series approximation to the stress relaxation function is introduced, and this in turn is used to derive various...These solutions are useful for verifying the model implementation. nonlinear, viscoelastic, rate-dependence, nearly incompressible, Prony series...12 3.4 Prony Series Approximation and Incremental Relations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.4.1
Efficient Parallel Algorithms for Unsteady Incompressible Flows
Guermond, Jean-Luc
2013-01-01
The objective of this paper is to give an overview of recent developments on splitting schemes for solving the time-dependent incompressible Navier–Stokes equations and to discuss possible extensions to the variable density/viscosity case. A particular attention is given to algorithms that can be implemented efficiently on large parallel clusters.
Lattice Boltzmann model for incompressible axisymmetric flows.
Chen, Sheng; Tölke, Jonas; Geller, Sebastian; Krafczyk, Manfred
2008-10-01
A lattice Boltzmann model for incompressible axisymmetric flow is proposed in this paper. Unlike previous axisymmetric lattice Boltzmann models, which were based on "primitive-variables" Navier-Stokes equations, the target macroscopic equations of the present model are vorticity-stream-function formulations. Due to the intrinsic features of vorticity-stream-function formulations, the present model is more efficient, more stable, and much simpler than the existing models. The advantages of the present model are validated by numerical experiments.
Waves of pressure in viscous incompressible fluid
Prosviryakov, E. Yu.
2017-12-01
A three-dimensional non-stationary flow of a viscous incompressible fluid in the infinite space is examined. The description of possible shapes of pressure is based on the equation for the axial component of velocity, which is an exact consequence of the basic equations. New analytical exact solutions to the Navier-Stokes equations for periodic and localized traveling waves have been found.
Inviscid incompressible limits for rotating fluids
Czech Academy of Sciences Publication Activity Database
Caggio, Matteo; Nečasová, Šárka
2017-01-01
Roč. 163, November (2017), s. 1-18 ISSN 0362-546X R&D Projects: GA ČR GA16-03230S Institutional support: RVO:67985840 Keywords : compressible Navier-Stokces system * rotating fluids * incompressible limit Subject RIV: BA - General Mathematics Impact factor: 1.192, year: 2016 http://www.sciencedirect.com/science/article/pii/S0362546X17301815?via%3Dihub
Surface wave propagation in a fluid-saturated incompressible ...
Indian Academy of Sciences (India)
Keywords. Incompressible porous medium; volume fractions; frequency equation; phase velocity; wave number; attenuation coefﬁcient. ... and discussed. As a particular case, the propagation of Rayleigh type surface waves at the free surface of an incompressible porous half-space is also deduced and discussed.
CUDA Simulation of Homogeneous, Incompressible Turbulence
Morin, Lee; Shebalin, John V.; Shum, Victor; Fu, Terry
2011-01-01
We discuss very fast Compute Unified Device Architecture (CUDA) simulations of ideal homogeneous incompressible turbulence based on Fourier models. These models have associated statistical theories that predict that Fourier coefficients of fluid velocity and magnetic fields (if present) are zero-mean random variables. Prior numerical simulations have shown that certain coefficients have a non-zero mean value that can be very large compared to the associated standard deviation. We review the theoretical basis of this "broken ergodicity" as applied to 2-D and 3-D fluid and magnetohydrodynamic simulations of homogeneous turbulence. Our new simulations examine the phenomenon of broken ergodicity through very long time and large grid size runs performed on a state-of-the-art CUDA platform. Results comparing various CUDA hardware configurations and grid sizes are discussed. NS and MHD results are compared.
Error estimation and adaptivity for incompressible hyperelasticity
Whiteley, J.P.
2014-04-30
SUMMARY: A Galerkin FEM is developed for nonlinear, incompressible (hyper) elasticity that takes account of nonlinearities in both the strain tensor and the relationship between the strain tensor and the stress tensor. By using suitably defined linearised dual problems with appropriate boundary conditions, a posteriori error estimates are then derived for both linear functionals of the solution and linear functionals of the stress on a boundary, where Dirichlet boundary conditions are applied. A second, higher order method for calculating a linear functional of the stress on a Dirichlet boundary is also presented together with an a posteriori error estimator for this approach. An implementation for a 2D model problem with known solution, where the entries of the strain tensor exhibit large, rapid variations, demonstrates the accuracy and sharpness of the error estimators. Finally, using a selection of model problems, the a posteriori error estimate is shown to provide a basis for effective mesh adaptivity. © 2014 John Wiley & Sons, Ltd.
Edge instability in incompressible planar active fluids
Nesbitt, David; Pruessner, Gunnar; Lee, Chiu Fan
2017-12-01
Interfacial instability is highly relevant to many important biological processes. A key example arises in wound healing experiments, which observe that an epithelial layer with an initially straight edge does not heal uniformly. We consider the phenomenon in the context of active fluids. Improving upon the approximation used by Zimmermann, Basan, and Levine [Eur. Phys. J.: Spec. Top. 223, 1259 (2014), 10.1140/epjst/e2014-02189-7], we perform a linear stability analysis on a two-dimensional incompressible hydrodynamic model of an active fluid with an open interface. We categorize the stability of the model and find that for experimentally relevant parameters, fingering instability is always absent in this minimal model. Our results point to the crucial role of density variation in the fingering instability in tissue regeneration.
Broken Ergodicity in Ideal, Homogeneous, Incompressible Turbulence
Morin, Lee; Shebalin, John; Fu, Terry; Nguyen, Phu; Shum, Victor
2010-01-01
We discuss the statistical mechanics of numerical models of ideal homogeneous, incompressible turbulence and their relevance for dissipative fluids and magnetofluids. These numerical models are based on Fourier series and the relevant statistical theory predicts that Fourier coefficients of fluid velocity and magnetic fields (if present) are zero-mean random variables. However, numerical simulations clearly show that certain coefficients have a non-zero mean value that can be very large compared to the associated standard deviation. We explain this phenomena in terms of broken ergodicity', which is defined to occur when dynamical behavior does not match ensemble predictions on very long time-scales. We review the theoretical basis of broken ergodicity, apply it to 2-D and 3-D fluid and magnetohydrodynamic simulations of homogeneous turbulence, and show new results from simulations using GPU (graphical processing unit) computers.
A Parallel Implicit Incompressible Flow Solver Using Unstructured Meshes.
1993-01-17
conjunction with the incompressible flow solver. Steady and unsteady flows over a tri-element airfoil and NACA0012 airfoil are computed using the...in a heated bath. Next, an explicit version of the incompressible flow solver is parallelized. This is applied for solving steady flow over a NACA0012 ...modified to accomodate a set of complete linelets within a subdomain. The algorithm was then tested via simulation of unsteady flow past NACA0012 airfoil
Current-sheet formation in incompressible electron magnetohydrodynamics
DEFF Research Database (Denmark)
Ruban, Victor P.
2002-01-01
The nonlinear dynamics of axisymmetric, as well as helical, frozen-in vortex structures is investigated by the Hamiltonian method in the framework of ideal incompressible electron magnetohydrodynamics. For description of current-sheet formation from a smooth initial magnetic field, local and nonl......The nonlinear dynamics of axisymmetric, as well as helical, frozen-in vortex structures is investigated by the Hamiltonian method in the framework of ideal incompressible electron magnetohydrodynamics. For description of current-sheet formation from a smooth initial magnetic field, local...
Surface wave propagation in a fluid-saturated incompressible ...
Indian Academy of Sciences (India)
... half-space is also deduced and discussed. Keywords. Incompressible porous medium; volume fractions; frequency equation; phase velocity; wave number; attenuation coefficient. 1. Introduction. Porous media theories play an important role in many branches of engineering including materials science, petroleum industry, ...
Roughness Induced Boundary Layer Transition in Incompressible Flow
Ye, Q.; Schrijer, F.J.; Scarano, F.
2015-01-01
The fluid dynamics process leading to laminar-turbulent transition behind an isolated roughness element is investigated in the incompressible regime using particle image velocimetry. The study covers the effect of roughness size and geometry on the promotion of transition. The measurement domain
Qualitative behaviour of incompressible two-phase flows with phase ...
Indian Academy of Sciences (India)
Jan Prüss
2017-11-07
Nov 7, 2017 ... with phase transitions is considered mathematically. The model is based on first ... is constant, i.e we consider the isothermal case. ν designates the outer normal of 1, V the normal velocity of (t), ... and ψ1,ψ2 be the given Helmholtz free energies, which are constants in the isothermal, incompressible case.
Real-Time Incompressible Fluid Simulation on the GPU
Directory of Open Access Journals (Sweden)
Xiao Nie
2015-01-01
Full Text Available We present a parallel framework for simulating incompressible fluids with predictive-corrective incompressible smoothed particle hydrodynamics (PCISPH on the GPU in real time. To this end, we propose an efficient GPU streaming pipeline to map the entire computational task onto the GPU, fully exploiting the massive computational power of state-of-the-art GPUs. In PCISPH-based simulations, neighbor search is the major performance obstacle because this process is performed several times at each time step. To eliminate this bottleneck, an efficient parallel sorting method for this time-consuming step is introduced. Moreover, we discuss several optimization techniques including using fast on-chip shared memory to avoid global memory bandwidth limitations and thus further improve performance on modern GPU hardware. With our framework, the realism of real-time fluid simulation is significantly improved since our method enforces incompressibility constraint which is typically ignored due to efficiency reason in previous GPU-based SPH methods. The performance results illustrate that our approach can efficiently simulate realistic incompressible fluid in real time and results in a speed-up factor of up to 23 on a high-end NVIDIA GPU in comparison to single-threaded CPU-based implementation.
An update on projection methods for transient incompressible viscous flow
Energy Technology Data Exchange (ETDEWEB)
Gresho, P.M.; Chan, S.T.
1995-07-01
Introduced in 1990 was the biharmonic equation (for the pressure) and the concomitant biharmonic miracle when transient incompressible viscous flow is solved approximately by a projection method. Herein is introduced the biharmonic catastrophe that sometimes occurs with these same projection methods.
On iterative methods for the incompressible Stokes problem
Rehman, M. ur; Geenen, T.; Vuik, C.; Segal, G.; MacLachlan, S.P.
2011-01-01
In this paper, we discuss various techniques for solving the system of linear equations that arise from the discretization of the incompressible Stokes equations by the finite-element method. The proposed solution methods, based on a suitable approximation of the Schur-complement matrix, are shown
Wind Turbine Aerodynamics Using an Incompressible Overset Grid Method
DEFF Research Database (Denmark)
Zahle, Frederik; Johansen, Jeppe; Sørensen, Niels
2007-01-01
In this paper 3D Navier-Stokes simulations of the unsteady flow over the NREL Phase VI turbine are presented. The computations are carried out using the structured grid, incompressible, finite volume flow solver EllipSys3D, which has been extended to include the use of overset grids. Computations...
An example of self–acceleration for incompressible flows
Directory of Open Access Journals (Sweden)
Jens Lorenz
2013-12-01
Full Text Available In this paper we consider the Cauchy problem for the unforced Eulerand Navier–Stokes equations for incompressible flows. We give an example of a smooth initial velocity field of finite energy which is self-accelerating, i.e., the maximal speed increases for some time. The self–acceleration is due to the non–Bernoulli part of the pressure generated by the velocity field.
Stability of axisymmetric swirl flows of viscous incompressible fluid
Aktershev, S. P.; Kuibin, P. A.
2013-09-01
A new method of solution to the problem of stability of the swirl flow of viscous incompressible fluid is developed. The method based on expansion of the required function into power series of radial coordinate allows an avoidance of difficulties related to numerical integration of the system of differential equations with a singular point. Stability of the Poiseuille flow in a rotating pipe is considered as an example.
A stabilised nonconforming finite element method for steady incompressible flows
Huang, Pengzhan; Feng, Xinlong; Liu, Demin
2012-02-01
A stabilised nonconforming finite element method for the steady incompressible flow problem with damping based on local Gauss integration is considered in this article. The method combines the nonconforming finite element method with the stabilised strategy. Moreover, the stability and error estimates are analysed. Finally, numerical results are shown to support the developed theory analysis. Compared with some classical, closely related mixed finite element methods, the results of the present method show its better performance than others.
Meshless Solution of Incompressible Flow Over Backward-Facing Step
Directory of Open Access Journals (Sweden)
Mužík Juraj
2016-05-01
Full Text Available Article presents the use of the meshless method for numerical simulation of incompressible fluid flow. The article presents the implementation of the meshless local Petrov-Galerkin method (MLPG, with Navier-Stokes equation formulated using the local weighted residual principle. The trial function construction process is the most important part of the meshless method implementation. In this article the radial basis functions (RBF are used for the process of the trial functions construction.
Divergence-Free SPH for Incompressible and Viscous Fluids.
Bender, Jan; Koschier, Dan
2017-03-01
In this paper we present a novel Smoothed Particle Hydrodynamics (SPH) method for the efficient and stable simulation of incompressible fluids. The most efficient SPH-based approaches enforce incompressibility either on position or velocity level. However, the continuity equation for incompressible flow demands to maintain a constant density and a divergence-free velocity field. We propose a combination of two novel implicit pressure solvers enforcing both a low volume compression as well as a divergence-free velocity field. While a compression-free fluid is essential for realistic physical behavior, a divergence-free velocity field drastically reduces the number of required solver iterations and increases the stability of the simulation significantly. Thanks to the improved stability, our method can handle larger time steps than previous approaches. This results in a substantial performance gain since the computationally expensive neighborhood search has to be performed less frequently. Moreover, we introduce a third optional implicit solver to simulate highly viscous fluids which seamlessly integrates into our solver framework. Our implicit viscosity solver produces realistic results while introducing almost no numerical damping. We demonstrate the efficiency, robustness and scalability of our method in a variety of complex simulations including scenarios with millions of turbulent particles or highly viscous materials.
Experiments on the Richtmyer-Meshkov Instability of Incompressible Fluids
Jacobs, J.; Niederhaus, C.
2000-01-01
Richtmyer-Meshkov (R-M) instability occurs when two different density fluids are impulsively accelerated in the direction normal to their nearly planar interface. The instability causes small perturbations on the interface to grow and possibly become turbulent given the proper initial conditions. R-M instability is similar to the Rayleigh-Taylor (R-T) instability, which is generated when the two fluids undergo a constant acceleration. R-M instability is a fundamental fluid instability that is important to fields ranging from astrophysics to high-speed combustion. For example, R-M instability is currently the limiting factor in achieving a net positive yield with inertial confinement fusion. The experiments described here utilize a novel technique that circumvents many of the experimental difficulties previously limiting the study of the R-M instability. A Plexiglas tank contains two unequal density liquids and is gently oscillated horizontally to produce a controlled initial fluid interface shape. The tank is mounted to a sled on a high speed, low friction linear rail system, constraining the main motion to the vertical direction. The sled is released from an initial height and falls vertically until it bounces off of a movable spring, imparting an impulsive acceleration in the upward direction. As the sled travels up and down the rails, the spring retracts out of the way, allowing the instability to evolve in free-fall until impacting a shock absorber at the end of the rails. The impulsive acceleration provided to the system is measured by a piezoelectric accelerometer mounted on the tank, and a capacitive accelerometer measures the low-level drag of the bearings. Planar Laser-Induced Fluorescence is used for flow visualization, which uses an Argon ion laser to illuminate the flow and a CCD camera, mounted to the sled, to capture images of the interface. This experimental study investigates the instability of an interface between incompressible, miscible liquids
The Theory of Nearly Incompressible Magnetohydrodynamic Turbulence: Homogeneous Description
Zank, G. P.; Adhikari, L.; Hunana, P.; Shiota, D.; Bruno, R.; Telloni, D.; Avinash, K.
2017-09-01
The theory of nearly incompressible magnetohydrodynamics (NI MHD) was developed to understand the apparent incompressibility of the solar wind and other plasma environments, particularly the relationship of density fluctuations to incompressible manifestations of turbulence in the solar wind and interstellar medium. Of interest was the identification of distinct leading-order incompressible descriptions for plasma beta β ≫ 1 and β ∼ 1 or ≪ 1 environments. In the first case, the “dimensionality” of the MHD description is 3D whereas for the latter two, there is a collapse of dimensionality in that the leading-order incompressible MHD description is 2D in a plane orthogonal to the large-scale or mean magnetic field. Despite the success of NI MHD in describing fluctuations in a low-frequency plasma environment such as the solar wind, a basic turbulence description has not been developed. Here, we rewrite the NI MHD system in terms of Elsässer variables. We discuss the distinction that emerges between the three cases. However, we focus on the β ∼ 1 or ≪ 1 regimes since these are appropriate to the solar wind and solar corona. In both cases, the leading-order turbulence model describes 2D turbulence and the higher-order description corresponds to slab turbulence, which forms a minority component. The Elsäasser β ∼ 1 or ≪ 1 formulation exhibits the nonlinear couplings between 2D and slab components very clearly, and shows that slab fluctuations respond in a passive scalar sense to the turbulently evolving majority 2D component fluctuations. The coupling of 2D and slab fluctuations through the β ∼ 1 or ≪ 1 NI MHD description leads to a very natural emergence of the “Goldreich-Sridhar” critical balance scaling parameter, although now with a different interpretation. Specifically, the critical balance parameter shows that the energy flux in wave number space is a consequence of the intensity of Alfvén wave sweeping versus passive scalar
Modeling electrokinetic flows by consistent implicit incompressible smoothed particle hydrodynamics
Pan, Wenxiao; Kim, Kyungjoo; Perego, Mauro; Tartakovsky, Alexandre M.; Parks, Michael L.
2017-04-01
We present a consistent implicit incompressible smoothed particle hydrodynamics (I2SPH) discretization of Navier-Stokes, Poisson-Boltzmann, and advection-diffusion equations subject to Dirichlet or Robin boundary conditions. It is applied to model various two and three dimensional electrokinetic flows in simple or complex geometries. The accuracy and convergence of the consistent I2SPH are examined via comparison with analytical solutions, grid-based numerical solutions, or empirical models. The new method provides a framework to explore broader applications of SPH in microfluidics and complex fluids with charged objects, such as colloids and biomolecules, in arbitrary complex geometries.
Modeling electrokinetic flows by consistent implicit incompressible smoothed particle hydrodynamics
Energy Technology Data Exchange (ETDEWEB)
Pan, Wenxiao; Kim, Kyungjoo; Perego, Mauro; Tartakovsky, Alexandre M.; Parks, Michael L.
2017-04-01
We present an efficient implicit incompressible smoothed particle hydrodynamics (I2SPH) discretization of Navier-Stokes, Poisson-Boltzmann, and advection-diffusion equations subject to Dirichlet or Robin boundary conditions. It is applied to model various two and three dimensional electrokinetic flows in simple or complex geometries. The I2SPH's accuracy and convergence are examined via comparison with analytical solutions, grid-based numerical solutions, or empirical models. The new method provides a framework to explore broader applications of SPH in microfluidics and complex fluids with charged objects, such as colloids and biomolecules, in arbitrary complex geometries.
Finite element solvers for incompressible fluid flows and heat transfer
Sohn, Jeong L.; Kim, Yongmo; Chung, T. J.
1989-01-01
Two different finite-element solvers for incompressible viscous flow, i.e., the mixed interpolation method and the SIMPLE-type iterative method, are compared and tested with some benchmark problems. The advantages of the SIMPLE-type iterative method are the decoupling of the governing equations and the use of equal-order interpolation functions for both velocity and pressure. Even though there is a significant difference between the two methods in terms of the pressure field, similar solutions are obtained for the velocity field.
Finite element solution algorithm for incompressible fluid dynamics
Baker, A. J.
1974-01-01
A finite element solution algorithm is established for the two-dimensional Navier-Stokes equations governing the transient motion of a viscous incompressible fluid, i.e., hydrodynamics. Dependent variable transformation renders the differential equation description uniformly elliptic. The finite element algorithm is established using the Galerkin criterion on a local basis within the Method of Weighted Residuals. It is unconstrained with respect to system linearity, computational mesh uniformity or solution domain closure regularity. The finite element matrices are established using a linear 'natural coordinate function' description. Computational solutions using the COMOC computer program illustrate the various features of the algorithm including recirculating flows.
Discrete Exterior Calculus Discretization of Incompressible Navier-Stokes Equations
Mohamed, Mamdouh S.
2017-05-23
A conservative discretization of incompressible Navier-Stokes equations over surface simplicial meshes is developed using discrete exterior calculus (DEC). Numerical experiments for flows over surfaces reveal a second order accuracy for the developed scheme when using structured-triangular meshes, and first order accuracy otherwise. The mimetic character of many of the DEC operators provides exact conservation of both mass and vorticity, in addition to superior kinetic energy conservation. The employment of barycentric Hodge star allows the discretization to admit arbitrary simplicial meshes. The discretization scheme is presented along with various numerical test cases demonstrating its main characteristics.
Pseudo-compressibility methods for the incompressible flow equations
Turkel, Eli; Arnone, A.
1993-01-01
Preconditioning methods to accelerate convergence to a steady state for the incompressible fluid dynamics equations are considered. The analysis relies on the inviscid equations. The preconditioning consists of a matrix multiplying the time derivatives. Thus the steady state of the preconditioned system is the same as the steady state of the original system. The method is compared to other types of pseudo-compressibility. For finite difference methods preconditioning can change and improve the steady state solutions. An application to viscous flow around a cascade with a non-periodic mesh is presented.
A multilevel approximate projections for incompressible flow calculations
Energy Technology Data Exchange (ETDEWEB)
Howell, L.H. [Lawrence Livermore National Lab., CA (United States)
1994-12-31
An adaptive-mesh projection algorithm for unsteady, variable-density, incompressible flow at high Reynolds number has been developed in the Applied Mathematics Group at LLNL. A grid-based refinement scheme combines the theoretical efficiencies of adaptive methods with the computational advantages of uniform grids, while a second-order Godunov method provides a robust and accurate treatment of advection in the presence of discontinuities without excessive dissipation. This paper focuses on the work of the present author concerning the approximate projection itself, which involves the numerical inversion of the operator {del} {center_dot} (1/{rho}){del} on various subsets of the adaptive grid hierarchy.
A Fractional-Step Method Of Computing Incompressible Flow
Kwak, Dochan; Rosenfeld, Moshe; Vinokur, Marcel
1993-01-01
Method of computing time-dependent flow of incompressible, viscous fluid involves numerical solution of Navier-Stokes equations on two- or three-dimensional computational grid based on generalized curvilinear coordinates. Equations of method derived in primitive-variable formulation. Dependent variables are pressure at center of each cell of computational grid and volume fluxes across faces of each cell. Volume fluxes replace Cartesian components of velocity; these fluxes correspond to contravariant components of velocity multiplied by volume of computational cell, in staggered grid. Choice of dependent variables enables simple extension of previously developed staggered-grid approach to generalized curvilinear coordinates and facilitates enforcement of conservation of mass.
Microscopic statistical description of incompressible Navier-Stokes granular fluids
Tessarotto, Massimo; Mond, Michael; Asci, Claudio
2017-05-01
Based on the recently established Master kinetic equation and related Master constant H-theorem which describe the statistical behavior of the Boltzmann-Sinai classical dynamical system for smooth and hard spherical particles, the problem is posed of determining a microscopic statistical description holding for an incompressible Navier-Stokes fluid. The goal is reached by introducing a suitable mean-field interaction in the Master kinetic equation. The resulting Modified Master Kinetic Equation (MMKE) is proved to warrant at the same time the condition of mass-density incompressibility and the validity of the Navier-Stokes fluid equation. In addition, it is shown that the conservation of the Boltzmann-Shannon entropy can similarly be warranted. Applications to the plane Couette and Poiseuille flows are considered showing that they can be regarded as final decaying states for suitable non-stationary flows. As a result, it is shown that an arbitrary initial stochastic 1-body PDF evolving in time by means of MMKE necessarily exhibits the phenomenon of Decay to Kinetic Equilibrium (DKE), whereby the same 1-body PDF asymptotically relaxes to a stationary and spatially uniform Maxwellian PDF.
Incompressible material point method for free surface flow
Zhang, Fan; Zhang, Xiong; Sze, Kam Yim; Lian, Yanping; Liu, Yan
2017-02-01
To overcome the shortcomings of the weakly compressible material point method (WCMPM) for modeling the free surface flow problems, an incompressible material point method (iMPM) is proposed based on operator splitting technique which splits the solution of momentum equation into two steps. An intermediate velocity field is first obtained by solving the momentum equations ignoring the pressure gradient term, and then the intermediate velocity field is corrected by the pressure term to obtain a divergence-free velocity field. A level set function which represents the signed distance to free surface is used to track the free surface and apply the pressure boundary conditions. Moreover, an hourglass damping is introduced to suppress the spurious velocity modes which are caused by the discretization of the cell center velocity divergence from the grid vertexes velocities when solving pressure Poisson equations. Numerical examples including dam break, oscillation of a cubic liquid drop and a droplet impact into deep pool show that the proposed incompressible material point method is much more accurate and efficient than the weakly compressible material point method in solving free surface flow problems.
A sharp interface method for incompressible two-phase flows
Sussman, M.; Smith, K. M.; Hussaini, M. Y.; Ohta, M.; Zhi-Wei, R.
2007-02-01
We present a sharp interface method for computing incompressible immiscible two-phase flows. It couples the level-set and volume-of-fluid techniques and retains their advantages while overcoming their weaknesses. It is stable and robust even for large density and viscosity ratios on the order of 1000 to 1. The numerical method is an extension of the second-order method presented by Sussman [M. Sussman, A second order coupled levelset and volume of fluid method for computing growth and collapse of vapor bubbles, Journal of Computational Physics 187 (2003) 110-136] in which the previous method treated the gas pressure as spatially constant and the present method treats the gas as a second incompressible fluid. The new method yields solutions in the zero gas density limit which are comparable in accuracy to the method in which the gas pressure was treated as spatially constant. This improvement in accuracy allows one to compute accurate solutions on relatively coarse grids, thereby providing a speed-up over continuum or "ghost-fluid" methods.
Incompressible magnetohydrodynamic modes in the thin magnetically twisted flux tube
Cheremnykh, O. K.; Fedun, V.; Kryshtal, A. N.; Verth, G.
2017-08-01
Context. Observations have shown that twisted magnetic fields naturally occur, and indeed are omnipresent in the Sun's atmosphere. It is therefore of great theoretical interest in solar atmospheric waves research to investigate the types of magnetohydrodynamic (MHD) wave modes that can propagate along twisted magnetic flux tubes. Aims: Within the framework of ideal MHD, the main aim of this work is to investigate small amplitude incompressible wave modes of twisted magnetic flux tubes with m ≥ 1. The axial magnetic field strength inside and outside the tube will be allowed to vary, to ensure the results will not be restricted to only cold plasma equilibria conditions. Methods: The dispersion equation for these incompressible linear MHD wave modes was derived analytically by implementing the long wavelength approximation. Results: It is shown, in the long wavelength limit, that both the frequency and radial velocity profile of the m = 1 kink mode are completely unaffected by the choice of internal background magnetic twist. However, fluting modes with m ≥ 2 are sensitive to the particular radial profile of magnetic twist chosen. Furthermore, due to background twist, a low frequency cut-off is introduced for fluting modes that is not present for kink modes. From an observational point of view, although magnetic twist does not affect the propagation of long wavelength kink modes, for fluting modes it will either work for or against the propagation, depending on the direction of wave travel relative to the sign of the background twist.
Irreversibility analysis of magneto-hydrodynamic nanofluid flow injected through a rotary disk
Directory of Open Access Journals (Sweden)
Rashidi Mohammad Mehdi
2015-01-01
Full Text Available The non-linear Navier-Stokes equations governed on the nanofluid flow injected through a rotary porous disk in the presence of an external uniform vertical magnetic field can be changed to a system of non-linear partial differential equations by applying similar parameter. In this study, partial differential equations are analytically solved by the modified differential transform method, Pade differential transformation method to obtain self-similar functions of motion and temperature. A very good agreement is observed between the obtained results of Pade differential transformation method and those of previously published ones. Then it has become possible to do a comprehensive parametric analysis on the entropy generation in this case to demonstrate the effects of physical flow parameters such as magnetic interaction parameter, injection parameter, nanoparticle volume fraction, dimensionless temperature difference, rotational Brinkman number and the type of nanofluid on the problem.
Parabolized Navier-Stokes Code for Computing Magneto-Hydrodynamic Flowfields
Mehta, Unmeel B. (Technical Monitor); Tannehill, J. C.
2003-01-01
This report consists of two published papers, 'Computation of Magnetohydrodynamic Flows Using an Iterative PNS Algorithm' and 'Numerical Simulation of Turbulent MHD Flows Using an Iterative PNS Algorithm'.
Magneto Hydrodynamic Simulations of a Magnetic Flux Compression Generator Using ALE3D
2017-07-13
cylindrical armature where an explosive drives the armature radially and causes a drop in the inductance. In this report, the results of ALE3D magneto...require adequate resolution to ensure convergence of the solution. If the mesh resolution is too coarse, numerical errors may become significant and...Letter “A” marks the point of crowbar impact caused by the downward spike. The simulation result shows the end-effect (a bell-shaped contour of
Comparison of magnetic island stabilization strategies from magneto-hydrodynamic simulations
Février, O.; Maget, P.; Lütjens, H.; Beyer, P.
2017-04-01
The degradation of plasma confinement in tokamaks caused by magnetic islands motivates to better understand their possible suppression using electron cyclotron current drive (ECCD) and to investigate the various strategies relevant for this purpose. In this work, we evaluate the efficiency of several control methods through nonlinear simulations of this process with the toroidal magneto-hydro-dynamic (MHD) code XTOR-2F (Lütjens and Luciani 2010 J. Comput. Phys. 229 8130-43), which has been extended to incorporate in Ohm’s law a source term modeling the driven current resulting from the interaction of the EC waves with the plasma. A basic control system has been implemented in the code, allowing testing of advanced strategies that require feedback on island position or phase. We focus in particular on the robustness of the control strategies towards uncertainties that apply to the control and ECCD systems, such as the risk of misalignment of the current deposition or the possible inability to generate narrow current deposition.
Magneto-hydrodynamics of coupled fluid–sheet interface with mass suction and blowing
Energy Technology Data Exchange (ETDEWEB)
Ahmad, R., E-mail: uqrahma3@uq.edu.au
2016-01-15
There are large number of studies which prescribe the kinematics of the sheet and ignore the sheet's mechanics. However, the current boundary layer analysis investigates the mechanics of both the electrically conducting fluid and a permeable sheet, which makes it distinct from the other studies in the literature. One of the objectives of the current study is to (i) examine the behaviour of magnetic field effect for both the surface and the electrically conducting fluid (ii) investigate the heat and mass transfer between a permeable sheet and the surrounding electrically conducting fluid across the hydro, thermal and mass boundary layers. Self-similar solutions are obtained by considering the RK45 technique. Analytical solution is also found for the stretching sheet case. The skin friction dual solutions are presented for various types of sheet. The influence of pertinent parameters on the dimensionless velocity, shear stress, temperature, mass concentration, heat and mass transfer rates on the fluid–sheet interface is presented graphically as well as numerically. The obtained results are of potential benefit for studying the electrically conducting flow over various soft surfaces such as synthetic plastics, soft silicone sheet and soft synthetic rubber sheet. These surfaces are easily deformed by thermal fluctuations or thermal stresses. - Highlights: • The momentum equation is modelled for both the surrounding MHD fluid and the sheet with the effects of mass suction and blowing. • The current study further investigates the heat and mass transfer characteristics between a permeable sheet and the surrounding electrically conducting fluid across the thermal and mass boundary layers. • Both the approximated and analytical techniques have been included for the purpose of comparison, and the perfect numerical agreements have been established with the previous studies. • Dual solutions for the skin friction coefficients are found for various categories of the sheet. • The movement of an electrically conducting fluid over an elastic sheet is much slower as compared to a stretching sheet. • A high viscous fluid such as oil has slow down the ow over an elastic stretching sheet and, as a result, the electrically conducting fluid having high viscosity will appear to coat the sheet, whereas the viscosity of water has rapidly increased the motion of an electrically conducting fluid over an elastic stretching sheet. • The study is applicable to a system involving fluid flow over various types of soft surfaces such as synthetic plastics, soft synthetic rubber sheet and fibres. Thus, the main contribution of this study is the depth of fluid flow analysis on the fluid–sheet interface and it's applications in engineering, which attract the readers.
Three Dimensional Magneto-Hydrodynamics Simulations of Auto-Magnetizing Imploding Liners for ICF
Woolstrum, Jeff; Jennings, Chris; Shipley, Gabriel; Awe, Thomas; Slutz, Stephen; Jordan, Nicholas; Lau, Yy; Peterson, Kyle; McBride, Ryan
2017-10-01
AutoMag is a potential next step in the magnetized liner inertial fusion (MagLIF) program. In standard MagLIF, external coils are used to magnetize deuterium gas inside a metal cylindrical liner, which is imploded by the Z-machine at Sandia National Laboratories. In AutoMag, helical slots are cut into the liner and filled with dielectric insulator to form a solenoid, producing an axial magnetic field from the drive current and removing the need for external field coils. Alternatively with external field coils, AutoMag could produce a field-reversed configuration inside the liner. Recent work at Sandia has found that the breakdown of the dielectric material corresponds to the geometry of the liner/dielectric. We explore this finding in 3D resistive-MHD simulations, modeling geometries relevant to both the 20-MA Z facility, and to the 1-MA MAIZE facility at the University of Michigan. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc. for the U.S. DoE's NNSA under contract DE-NA0003525.
Exponential integrators for the incompressible Navier-Stokes equations.
Energy Technology Data Exchange (ETDEWEB)
Newman, Christopher K.
2004-07-01
We provide an algorithm and analysis of a high order projection scheme for time integration of the incompressible Navier-Stokes equations (NSE). The method is based on a projection onto the subspace of divergence-free (incompressible) functions interleaved with a Krylov-based exponential time integration (KBEI). These time integration methods provide a high order accurate, stable approach with many of the advantages of explicit methods, and can reduce the computational resources over conventional methods. The method is scalable in the sense that the computational costs grow linearly with problem size. Exponential integrators, used typically to solve systems of ODEs, utilize matrix vector products of the exponential of the Jacobian on a vector. For large systems, this product can be approximated efficiently by Krylov subspace methods. However, in contrast to explicit methods, KBEIs are not restricted by the time step. While implicit methods require a solution of a linear system with the Jacobian, KBEIs only require matrix vector products of the Jacobian. Furthermore, these methods are based on linearization, so there is no non-linear system solve at each time step. Differential-algebraic equations (DAEs) are ordinary differential equations (ODEs) subject to algebraic constraints. The discretized NSE constitute a system of DAEs, where the incompressibility condition is the algebraic constraint. Exponential integrators can be extended to DAEs with linear constraints imposed via a projection onto the constraint manifold. This results in a projected ODE that is integrated by a KBEI. In this approach, the Krylov subspace satisfies the constraint, hence the solution at the advanced time step automatically satisfies the constraint as well. For the NSE, the projection onto the constraint is typically achieved by a projection induced by the L{sup 2} inner product. We examine this L{sup 2} projection and an H{sup 1} projection induced by the H{sup 1} semi-inner product. The H
Structure and computation of two-dimensional incompressible extended MHD
Grasso, D; Abdelhamid, H M; Morrison, P J
2016-01-01
A comprehensive study of a reduced version of Lust's equations, the extended magnetohydrodynamic (XMHD) model obtained from the two-fluid theory for electrons and ions with the enforcement of quasineutrality, is given. Starting from the Hamiltonian structure of the fully three-dimensional theory, a Hamiltonian two-dimensional incompressible four-field model is derived. In this way energy conservation along with four families of Casimir invariants are naturally obtained. The construction facilitates various limits leading to the Hamiltonian forms of Hall, inertial, and ideal MHD, with their conserved energies and Casimir invariants. Basic linear theory of the four-field model is treated, and the growth rate for collisionless reconnection is obtained. Results from nonlinear simulations of collisionless tearing are presented and interpreted using, in particular normal fields, a product of the Hamiltonian theory that gives rise to simplified equations of motion.
Effects of Nuclear Incompressibility on Heavy-Ion Fusion
Esbensen, Henning; Mişicu, Şerban
2008-08-01
We apply the coupled-channels technique to study the hindrance of fusion which has been observed at extreme sub-barrier energies in 64Ni+64Ni and 16O+208Pb collisions. The calculated fusion cross section is sensitive at extreme subbarrier energies to the ion-ion potential for overlapping nuclei but we are not able to reproduce the low-energy data when we apply a conventional Woods-Saxon or proximity type potential in the calculations. The data can, however, be explained quite well by applying the M3Y double-folding potential which has been corrected for the effect of the nuclear incompressibility. The correction is made by including a repulsive contact interaction in the double-folding procedure. This produces a thicker Coulomb barrier and rather shallow pocket in the entrance channel potential, and these two features make it possible to explain the fusion data at the lowest energies.
Symmetry Breaking for the Incompressible Navier-Stokes Equations
Waymire, E. C.; Dascaliuc, R.; Thomann, E. A.; Michalowski, N. P.
2015-12-01
The validity of uniquely determined solutions to 3-dimensional incompressible Navier-Stokes equations for smooth initial data remains one of the great challenges since their inception. Jean Leray was among the first investigage the mathematical mysteries embodied by these equations in terms of self-similarities viewed backwards in time. However this proved to be uneventful, and recently shown to be a failed approach. Recent new developments in the mathematical representation of solutions as expected values of stochastic cascades have lead to new insights into the nature of self-similarities in forward in time solutions to these equations. The purpose of this talk is to describe some of the progress and challenges underlying these fundamentally important equations for fluid flow when viewed from this perspective.
Liao, Xian; Liu, Yanlin
2016-01-01
The present work is devoted to proving that the boundary regularity of the three dimensional density patch persists by time evolution for inhomogeneous incompressible viscous flow, with some smallness condition on the initial velocity.
Nurijanyan, S.; van der Vegt, Jacobus J.W.; Bokhove, Onno
2013-01-01
A discontinuous Galerkin finite element method (DGFEM) has been developed and tested for the linear, three-dimensional, rotating incompressible Euler equations. These equations admit complicated wave solutions, which poses numerical challenges. These challenges concern: (i) discretisation of a
Large scale finite element solvers for the large eddy simulation of incompressible turbulent flows
Colomés Gené, Oriol
2016-01-01
In this thesis we have developed a path towards large scale Finite Element simulations of turbulent incompressible flows. We have assessed the performance of residual-based variational multiscale (VMS) methods for the large eddy simulation (LES) of turbulent incompressible flows. We consider VMS models obtained by different subgrid scale approximations which include either static or dynamic subscales, linear or nonlinear multiscale splitting, and different choices of the subscale space. W...
Weakly nonlinear incompressible Rayleigh-Taylor instability in spherical geometry
Zhang, J.; Wang, L. F.; Ye, W. H.; Wu, J. F.; Guo, H. Y.; Zhang, W. Y.; He, X. T.
2017-06-01
In this research, a weakly nonlinear (WN) model for the incompressible Rayleigh-Taylor instability in cylindrical geometry [Wang et al., Phys. Plasmas 20, 042708 (2013)] is generalized to spherical geometry. The evolution of the interface with an initial small-amplitude single-mode perturbation in the form of Legendre mode (Pn) is analysed with the third-order WN solutions. The transition of the small-amplitude perturbed spherical interface to the bubble-and-spike structure can be observed by our model. For single-mode perturbation Pn, besides the generation of P 2 n and P 3 n , which are similar to the second and third harmonics in planar and cylindrical geometries, many other modes in the range of P0- P 3 n are generated by mode-coupling effects up to the third order. With the same initial amplitude, the bubbles at the pole grow faster than those at the equator in the WN regime. Furthermore, it is found that the behavior of the bubbles at the pole is similar to that of three-dimensional axisymmetric bubbles, while the behavior of the bubbles at the equator is similar to that of two-dimensional bubbles.
Global Regularity for Several Incompressible Fluid Models with Partial Dissipation
Wu, Jiahong; Xu, Xiaojing; Ye, Zhuan
2017-09-01
This paper examines the global regularity problem on several 2D incompressible fluid models with partial dissipation. They are the surface quasi-geostrophic (SQG) equation, the 2D Euler equation and the 2D Boussinesq equations. These are well-known models in fluid mechanics and geophysics. The fundamental issue of whether or not they are globally well-posed has attracted enormous attention. The corresponding models with partial dissipation may arise in physical circumstances when the dissipation varies in different directions. We show that the SQG equation with either horizontal or vertical dissipation always has global solutions. This is in sharp contrast with the inviscid SQG equation for which the global regularity problem remains outstandingly open. Although the 2D Euler is globally well-posed for sufficiently smooth data, the associated equations with partial dissipation no longer conserve the vorticity and the global regularity is not trivial. We are able to prove the global regularity for two partially dissipated Euler equations. Several global bounds are also obtained for a partially dissipated Boussinesq system.
Instantaneous Point Explosion in Incompressible Fluid-like Media
Grinfeld, Michael; Segletes, Steven
The problem of point explosion is one of the most famous and extensively developed in in the sense of corresponding physics, mechanics, and applied mathematics. There are many reasons for that based on its practical importance and theoretical beauty. We refer interested readers to the publications of Sedov, Taylor, Laudau and Lifshitz, and Lavrent'ev and Shabat. In the paper, we discuss this classical program from the standpoint of terminal ballistics and present our novel results relating to the special situation when the media can be treated as an ``effective'' incompressible liquid. Sedov, L.I., Similarity and Dimensional Methods in Mechanics, CRC Press, 1993. Taylor, J., Explosion. II. The Atomic Explosion of 1945. Proc. Roy. Soc. London, A201, ¹ 1065, 1950, p. 175. Landau, L.D. and Lifshitz, E.M., Fluid Mechanics, Pergamon Press, 1959. Zeldovich Ya. B. and Raizer, Yu.P., Physics of Shock Waves and High-Temperature Hydrodynamic Phenomena,Dover, New York, 2002. Lavrent'ev, M.A. and Shabat, B.V., Hydrodynamic Phenomena and Their Mathematical Models. Hauka, 1973 (in Russian).
Multidimensional upwinding for incompressible flows based on characteristics
Zamzamian, Kamiar; Razavi, Seyed Esmail
2008-10-01
In this paper, the multidimensional characteristic based upwind scheme (MCB) which has been recently introduced by the authors is applied to two another benchmark problems namely flow in a channel with a backward facing step and two-dimensional steady and unsteady flows past a circular cylinder. Extension of MCB scheme for calculating convective fluxes on non-Cartesian grids is presented here. For the flow over backward facing step, obtained results were compared against well-known experimental data and the results show high accuracy of MCB scheme and faster convergence rate with respect to conventional CB scheme. In the case of flow over circular cylinder, the flow at steady and transient regimes is investigated by MCB scheme. Again, the results obtained by MCB are compared to the other results in the literature and show good agreement with them. Also, rapid convergence rate of MCB was observed in this case too. It is concluded that, the genuinely multidimensional characteristic based (MCB) scheme, has been introduced earlier by the authors, is a robust and powerful scheme for modeling incompressible viscous flows for achieving the high accuracy and remarkable advantage in convergence rate with respect to conventional characteristic based schemes.
Éléments finis pour les fluides incompressibles
Azaïez, Mejdi; Mund, Ernest
2011-01-01
Cet ouvrage présente l'ensemble des concepts et méthodes nécessaires à la modélisation numérique par éléments finis du comportement des fluides visqueux newtoniens incompressibles. Après un bref rappel des équations de base et des modèles simplifiés, il expose en détail les techniques d'approximation de ces équations par éléments finis pour les dépendances spatiale et temporelle (problèmes de diffusion, d'advection-diffusion et de transport). Une attention toute particulière est portée à la discrétisation spatiale des équations de Stokes et aux algorithmes temporels pour la simulation numérique directe des équations de Navier-Stokes. Un chapitre ancillaire résume les méthodes de résolution des systèmes algébriques de grande taille à structure creuse, caractéristiques des méthodes d'éléments finis. L'exposé clair, didactique et progressif offre un contenu équilibré entre théorie et pratique. Ce manuel constitue ainsi une référence indispensable pour les étudiants de ma...
Rouze, Ned C; Wang, Michael H; Palmeri, Mark L; Nightingale, Kathy R
2013-11-15
Elastic properties of materials can be measured by observing shear wave propagation following localized, impulsive excitations and relating the propagation velocity to a model of the material. However, characterization of anisotropic materials is difficult because of the number of elasticity constants in the material model and the complex dependence of propagation velocity relative to the excitation axis, material symmetries, and propagation directions. In this study, we develop a model of wave propagation following impulsive excitation in an incompressible, transversely isotropic (TI) material such as muscle. Wave motion is described in terms of three propagation modes identified by their polarization relative to the material symmetry axis and propagation direction. Phase velocities for these propagation modes are expressed in terms of five elasticity constants needed to describe a general TI material, and also in terms of three constants after the application of two constraints that hold in the limit of an incompressible material. Group propagation velocities are derived from the phase velocities to describe the propagation of wave packets away from the excitation region following localized excitation. The theoretical model is compared to the results of finite element (FE) simulations performed using a nearly incompressible material model with the five elasticity constants chosen to preserve the essential properties of the material in the incompressible limit. Propagation velocities calculated from the FE displacement data show complex structure that agrees quantitatively with the theoretical model and demonstrates the possibility of measuring all three elasticity constants needed to characterize an incompressible, TI material. © 2013 Elsevier Ltd. All rights reserved.
Coarse-grained incompressible magnetohydrodynamics: analyzing the turbulent cascades
Aluie, Hussein
2017-02-01
We formulate a coarse-graining approach to the dynamics of magnetohydrodynamic (MHD) fluids at a continuum of length-scales ℓ. In this methodology, effective equations are derived for the observable velocity and magnetic fields spatially-averaged at an arbitrary scale of resolution. The microscopic equations for the ‘bare’ velocity and magnetic fields are ‘renormalized’ by coarse-graining to yield macroscopic effective equations that contain both a subscale stress and a subscale electromotive force (EMF) generated by nonlinear interaction of eliminated fields and plasma motions. Particular attention is given to the effects of these subscale terms on the balances of the quadratic invariants of ideal incompressible MHD—energy, cross-helicity and magnetic helicity. At large coarse-graining length-scales, the direct dissipation of the invariants by microscopic mechanisms (such as molecular viscosity and Spitzer resistivity) is shown to be negligible. The balance at large scales is dominated instead by the subscale nonlinear terms, which can transfer invariants across scales, and are interpreted in terms of work concepts for energy and in terms of topological flux-linkage for the two helicities. An important application of this approach is to MHD turbulence, where the coarse-graining length ℓ lies in the inertial cascade range. We show that in the case of sufficiently rough velocity and/or magnetic fields, the nonlinear inter-scale transfer need not vanish and can persist to arbitrarily small scales. Although closed expressions are not available for subscale stress and subscale EMF, we derive rigorous upper bounds on the effective dissipation they produce in terms of scaling exponents of the velocity and magnetic fields. These bounds provide exact constraints on phenomenological theories of MHD turbulence in order to allow the nonlinear cascade of energy and cross-helicity. On the other hand, we prove a very strong version of the Woltjer-Taylor conjecture
Numerical simulation by cubic-polynomial interpolation for unsteady, incompressible, viscous flow
Sugiyama, Hiromi
1995-01-01
A procedure for computing time-accurate solutions to the incompressible Navier-Stokes equations is presented. The procedure, designated as the CIP-ACE method, uses (1) an artificial compressibility approach to transform the equations into a hyperbolic system, (2) a fractional-step-like approach, and (3) cubic-polynomial interpolation to upwind difference the N-S equations. Two sample incompressible flow problems with known exact solutions were used to validate this CIP-ACE method. The method showed rapid convergence to a numerical solution that is reasonably compatible with the exact solutions. Furthermore, it can be extended to solve the three-dimensional, incompressible N-S equations in generalized coordinates, making it an attractive alternative to more established numerical methods.
A comparison of two incompressible Navier-Stokes algorithms for unsteady internal flow
Wiltberger, N. Lyn; Rogers, Stuart E.; Kwak, Dochan
1993-01-01
A comparative study of two different incompressible Navier-Stokes algorithms for solving an unsteady, incompressible, internal flow problem is performed. The first algorithm uses an artificial compressibility method coupled with upwind differencing and a line relaxation scheme. The second algorithm uses a fractional step method with a staggered grid, finite volume approach. Unsteady, viscous, incompressible, internal flow through a channel with a constriction is computed using the first algorithm. A grid resolution study and parameter studies on the artificial compressibility coefficient and the maximum allowable residual of the continuity equation are performed. The periodicity of the solution is examined and several periodic data sets are generated using the first algorithm. These computational results are compared with previously published results computed using the second algorithm and experimental data.
Phase-field modeling of isothermal quasi-incompressible multicomponent liquids
Tóth, Gyula I.
2016-09-01
In this paper general dynamic equations describing the time evolution of isothermal quasi-incompressible multicomponent liquids are derived in the framework of the classical Ginzburg-Landau theory of first order phase transformations. Based on the fundamental equations of continuum mechanics, a general convection-diffusion dynamics is set up first for compressible liquids. The constitutive relations for the diffusion fluxes and the capillary stress are determined in the framework of gradient theories. Next the general definition of incompressibility is given, which is taken into account in the derivation by using the Lagrange multiplier method. To validate the theory, the dynamic equations are solved numerically for the quaternary quasi-incompressible Cahn-Hilliard system. It is demonstrated that variable density (i) has no effect on equilibrium (in case of a suitably constructed free energy functional) and (ii) can influence nonequilibrium pattern formation significantly.
Brinkhues, S; Klawonn, A; Rheinbach, O; Schröder, J
2013-03-01
Arterial walls in the healthy physiological regime are characterized by quasi-incompressible, anisotropic, hyperelastic material behavior. Polyconvex material functions representing such materials typically incorporate a penalty function to account for the incompressibility. Unfortunately, the penalty will affect the conditioning of the stiffness matrices. For high penalty parameters, the performance of iterative solvers will degrade, and when direct solvers are used, the quality of the solutions will deteriorate. In this paper, an augmented Lagrange approach is used to cope with the quasi-incompressibility condition. Here, the penalty parameter can be chosen much smaller, and as a consequence, the arising linear systems of equations have better properties. An improved convergence is then observed for the finite element tearing and interconnecting-dual primal domain decomposition method, which is used as an iterative solver. Numerical results for an arterial geometry obtained from ultrasound imaging are presented. Copyright © 2012 John Wiley & Sons, Ltd.
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Jilian Wu
2013-01-01
Full Text Available We discuss several stabilized finite element methods, which are penalty, regular, multiscale enrichment, and local Gauss integration method, for the steady incompressible flow problem with damping based on the lowest equal-order finite element space pair. Then we give the numerical comparisons between them in three numerical examples which show that the local Gauss integration method has good stability, efficiency, and accuracy properties and it is better than the others for the steady incompressible flow problem with damping on the whole. However, to our surprise, the regular method spends less CPU-time and has better accuracy properties by using Crout solver.
On the method of pseudo compressibility for numerically solving incompressible flows
Chang, J. L. C.; Kwak, D.
1984-01-01
Pseudo compressibility is used for numerically solving incompressible flows to achieve computational efficiency. The use of pseudo compressibility results in a system of hyperbolic-type equations of motion that introduce waves of finite speed. The interactions of the wave propagation and the vorticity spreading are analyzed. A criterion governing the dependence of the pseudo compressiblity on the Reynolds number and the characteristic length of the flow geometry is obtained that allows for a proper convergence. It is demonstrated that the solution does tend to the incompressible limit. External and internal viscous flow test problems are presented to verify the theory.
Czech Academy of Sciences Publication Activity Database
Šístek, Jakub; Cirak, F.
2015-01-01
Roč. 122, 20 November (2015), s. 165-183 ISSN 0045-7930 R&D Projects: GA ČR GA14-02067S Institutional support: RVO:67985840 Keywords : Navier-Stokes * incompressible flow * Krylov subspace methods Subject RIV: BA - General Mathematics Impact factor: 1.891, year: 2015 http://www.sciencedirect.com/science/article/pii/S0045793015003023
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Chunhong Tian
2017-01-01
Full Text Available We are concerned with the regularity criterion for weak solutions to the 3D incompressible MHD equations in this paper. We show that if some partial derivatives of the velocity components and magnetic components belong to the multiplier spaces, then the solution actually is smooth on (0,T.
Labeur, R.J.; Wells, G.N.
2012-01-01
A hybrid method for the incompressible Navier–Stokes equations is presented. The ethod inherits the attractive stabilizing mechanism of upwinded discontinuous Galerkin methods hen momentum advection becomes significant, equal-order interpolations can be used for the velocity nd pressure fields, and
Pesch, L.; van der Vegt, Jacobus J.W.
2008-01-01
Using the generalized variable formulation of the Euler equations of fluid dynamics, we develop a numerical method that is capable of simulating the flow of fluids with widely differing thermodynamic behavior: ideal and real gases can be treated with the same method as an incompressible fluid. The
CSIR Research Space (South Africa)
Oxtoby, Oliver F
2012-05-01
Full Text Available In this paper we detail a fast, fully-coupled, partitioned fluid–structure interaction (FSI) scheme. For the incompressible fluid, new fractional-step algorithms are proposed which make possible the fully implicit, but matrixfree, parallel solution...
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S. Dastgeer
2005-01-01
Full Text Available Interstellar scintillation and angular radio wave broadening measurements show that interstellar and solar wind (electron density fluctuations exhibit a Kolmogorov-like k-5/3 power spectrum extending over many decades in wavenumber space. The ubiquity of the Kolmogorov-like interstellar medium (ISM density spectrum led to an explanation based on coupling incompressible magnetohydrodynamic (MHD fluctuations to density fluctuations through a 'pseudosound' relation within the context of 'nearly incompressible' (NI hydrodynamics (HD and MHD models. The NI theory provides a fundamentally different explanation for the observed ISM density spectrum in that the density fluctuations can be a consequence of passive scalar convection due to background incompressible fluctuations. The theory further predicts generation of long-scale structures and various correlations between the density, temperature and the (magneto acoustic as well as convective pressure fluctuations in the compressible ISM fluids in different thermal regimes that are determined purely by the thermal fluctuation level. In this paper, we present the results of our two dimensional nonlinear fluid simulations, exploring various nonlinear aspects that lead to inertial range ISM turbulence within the context of a NI hydrodymanics model. In qualitative agreement with the NI predictions and the in-situ observations, we find that i the density fluctuations exhibit a Kolmogorov-like spectrum via a passive convection in the field of the background incompressible fluctuations, ii the compressible ISM fluctuations form long scale flows and structures, and iii the density and the temperature fluctuations are anti-correlated.
Wind Turbine Rotor-Tower Interaction Using an Incompressible Overset Grid Method
DEFF Research Database (Denmark)
Zahle, Frederik; Johansen, Jeppe; Sørensen, Niels
2007-01-01
In this paper 3D Navier-Stokes simulations of the flow over the NREL Phase VI turbine are presented. The computations are carried out using the structured grid, incompressible, finite volume flow solver EllipSys3D, which has been extended to include the use of overset grids. Computations are pres...
On the Coupling of Incompressible Stokes or Navier–Stokes and Darcy Flows Through Porous Media
Girault, V.
2012-11-03
In this chapter, we present the theoretical analysis of coupled incompressible Navier-Stokes (or Stokes) flows and Darcy flows with the Beavers-Joseph-Saffman interface condition. We discuss alternative interface and porous media models. We review some finite element methods used by several authors in this coupling and present numerical experiments.
Nurijanyan, S.; van der Vegt, Jacobus J.W.; Bokhove, Onno
2011-01-01
A discontinuous Galerkin nite element method (DGFEM) has been developed and tested for linear, three-dimensional, rotating incompressible Euler equations. These equations admit complicated wave solutions. The numerical challenges concern: (i) discretisation of a divergence-free velocity eld; (ii)
A priori estimates for the free boundary problem of incompressible neo-Hookean elastodynamics
Hao, Chengchun; Wang, Dehua
2016-07-01
A free boundary problem for the incompressible neo-Hookean elastodynamics is studied in two and three spatial dimensions. The a priori estimates in Sobolev norms of solutions with the physical vacuum condition are established through a geometrical point of view of Christodoulou and Lindblad (2000) [3]. Some estimates on the second fundamental form and velocity of the free surface are also obtained.
Liska, Sebastian
2016-01-01
A new parallel, computationally efficient immersed boundary method for solving three-dimensional, viscous, incompressible flows on unbounded domains is presented. Immersed surfaces with prescribed motions are generated using the interpolation and regularization operators obtained from the discrete delta function approach of the original (Peskin's) immersed boundary method. Unlike Peskin's method, boundary forces are regarded as Lagrange multipliers that are used to satisfy the no-slip condition. The incompressible Navier-Stokes equations are discretized on an unbounded staggered Cartesian grid and are solved in a finite number of operations using lattice Green's function techniques. These techniques are used to automatically enforce the natural free-space boundary conditions and to implement a novel block-wise adaptive grid that significantly reduces the run-time cost of solutions by limiting operations to grid cells in the immediate vicinity and near-wake region of the immersed surface. These techniques also...
Mathematical problems of the dynamics of incompressible fluid on a rotating sphere
Skiba, Yuri N
2017-01-01
This book presents selected mathematical problems involving the dynamics of a two-dimensional viscous and ideal incompressible fluid on a rotating sphere. In this case, the fluid motion is completely governed by the barotropic vorticity equation (BVE), and the viscosity term in the vorticity equation is taken in its general form, which contains the derivative of real degree of the spherical Laplace operator. This work builds a bridge between basic concepts and concrete outcomes by pursuing a rich combination of theoretical, analytical and numerical approaches, and is recommended for specialists developing mathematical methods for application to problems in physics, hydrodynamics, meteorology and geophysics, as well for upper undergraduate or graduate students in the areas of dynamics of incompressible fluid on a rotating sphere, theory of functions on a sphere, and flow stability.
Maximum-Entropy Meshfree Method for Compressible and Near-Incompressible Elasticity
Energy Technology Data Exchange (ETDEWEB)
Ortiz, A; Puso, M A; Sukumar, N
2009-09-04
Numerical integration errors and volumetric locking in the near-incompressible limit are two outstanding issues in Galerkin-based meshfree computations. In this paper, we present a modified Gaussian integration scheme on background cells for meshfree methods that alleviates errors in numerical integration and ensures patch test satisfaction to machine precision. Secondly, a locking-free small-strain elasticity formulation for meshfree methods is proposed, which draws on developments in assumed strain methods and nodal integration techniques. In this study, maximum-entropy basis functions are used; however, the generality of our approach permits the use of any meshfree approximation. Various benchmark problems in two-dimensional compressible and near-incompressible small strain elasticity are presented to demonstrate the accuracy and optimal convergence in the energy norm of the maximum-entropy meshfree formulation.
Pradipto; Purqon, Acep
2017-07-01
Lattice Boltzmann Method (LBM) is the novel method for simulating fluid dynamics. Nowadays, the application of LBM ranges from the incompressible flow, flow in the porous medium, until microflows. The common collision model of LBM is the BGK with a constant single relaxation time τ. However, BGK suffers from numerical instabilities. These instabilities could be eliminated by implementing LBM with multiple relaxation time. Both of those scheme have implemented for incompressible 2 dimensions lid-driven cavity. The stability analysis has done by finding the maximum Reynolds number and velocity for converged simulations. The accuracy analysis is done by comparing the velocity profile with the benchmark results from Ghia, et al and calculating the net velocity flux. The tests concluded that LBM with MRT are more stable than BGK, and have a similar accuracy. The maximum Reynolds number that converges for BGK is 3200 and 7500 for MRT respectively.
The flow of an incompressible electroconductive fluid past a thin airfoil. The parabolic profile
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Adrian CARABINEANU
2014-04-01
Full Text Available We study the two-dimensional steady flow of an ideal incompressible perfectly conducting fluid past an insulating thin parabolic airfoil. We consider the linearized Euler and Maxwell equations and Ohm's law. We use the integral representations for the velocity, magnetic induction and pressure and the boundary conditions to obtain an integral equation for the jump of the pressure across the airfoil. We give some graphic representations for the lift coefficient, velocity and magnetic induction.
Decay of solutions to equations modelling incompressible bipolar non-newtonian fluids
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Bo-Qing Dong
2005-11-01
Full Text Available This article concerns systems of equations that model incompressible bipolar non-Newtonian fluid motion in the whole space $mathbb{R}^n$. Using the improved Fourier splitting method, we prove that a weak solution decays in the $L^2$ norm at the same rate as $(1+t^{-n/4}$ as the time $t$ approaches infinity. Also we obtain optimal $L^2$ error-estimates for Newtonian and Non-Newtonian flows.
Czech Academy of Sciences Publication Activity Database
Deuring, P.; Kračmar, S.; Nečasová, Šárka
2017-01-01
Roč. 68, č. 1 (2017), č. článku 16. ISSN 0044-2275 R&D Projects: GA ČR GA13-00522S Institutional support: RVO:67985840 Keywords : asymptotic profile * Pointwise decay * rotating body * stationary incompressible Navier–Stokes system Subject RIV: BA - General Mathematics Impact factor: 1.687, year: 2016 http://link.springer.com/article/10.1007%2Fs00033-016-0760-x
A p-version finite element method for steady incompressible fluid flow and convective heat transfer
Winterscheidt, Daniel L.
1993-01-01
A new p-version finite element formulation for steady, incompressible fluid flow and convective heat transfer problems is presented. The steady-state residual equations are obtained by considering a limiting case of the least-squares formulation for the transient problem. The method circumvents the Babuska-Brezzi condition, permitting the use of equal-order interpolation for velocity and pressure, without requiring the use of arbitrary parameters. Numerical results are presented to demonstrate the accuracy and generality of the method.
Parallel Solvers for Incompressible Navier-Stokes Equations and Scalable Tools for FEM Applications
K. Georgiev
2012-01-01
The White Paper content is focused on: a) construction and analysis of novel scalable algorithms to enhance scientific applications based on mesh methods (mainly on finite element method (FEM) technology); b) optimization of a new class of algorithms on many core systems. From one site, the commonly accepted benchmark problem in computational fluid dynamics (CFD) – time dependent system of incompressible Navier-Stokes equations, is considered. The activities were motivated by advanced larg...
Velocity-vorticity formulation of three-dimensional, steady, viscous, incompressible flows
Energy Technology Data Exchange (ETDEWEB)
Meir, A.J. [Auburn Univ., AL (United States)
1994-12-31
In this work we discuss some aspects of the velocity-vorticity formulation of three-dimensional, steady, viscous, incompressible flows. We describe reasonable boundary conditions that should be imposed on the vorticity and a compatibility condition that the vorticity must satisfy. This formulation may give rise to efficient numerical algorithms for approximating solutions of the Stokes problem, which in turn yields an iterative method for approximating solutions of the Navier-Stokes equations.
Guermond, J.-L.
2011-01-01
In this paper we analyze the convergence properties of a new fractional time-stepping technique for the solution of the variable density incompressible Navier-Stokes equations. The main feature of this method is that, contrary to other existing algorithms, the pressure is determined by just solving one Poisson equation per time step. First-order error estimates are proved, and stability of a formally second-order variant of the method is established. © 2011 Society for Industrial and Applied Mathematics.
Simulation of 3D unsteady incompressible flow past a NACA 0012 wing section
Jansson, Johan; Hoffman, Johan; Jansson, Niclas
2012-01-01
We present computational simulations of three-dimensional unsteady high Reynolds number incompressible flow past a NACA 0012 wing profile, for a range of angles of attack, from low lift through stall. A stabilized finite element method is used, referred to as General Galerkin (G2), with adaptive mesh refinement with respect to the error in target output, such as aerodynamic forces. Computational predictions of aerodynamic forces are validated against experimental data. QC 20120913
On the stabilization of finite volume methods with co-located variables for incompressible flow
Klaij, C. M.
2015-09-01
Finite volume methods with co-located variables for incompressible flow suffer from spurious pressure oscillations unless a stabilization method is applied. Variations of the pressure-weighed interpolation (PWI) method are typically used for this purpose. But the PWI method does not only prevent spurious oscillations. Counter-intuitively, it also simplifies the approximation of the Schur complement (pressure matrix) which appears in iterative solution methods such as SIMPLE.
Tripathi, D.; JORAR, R.; Beg, O. Anwar; Kadir, A.
2017-01-01
Biomimetic propulsion mechanisms are increasingly being explored in engineering sciences. Peristalsis is one of the most efficient of these mechanisms and offers considerable promise\\ud in microscale fluidics. Electrokinetic peristalsis has recently also stimulated significant attention. Electrical and magnetic fields also offer an excellent mode for regulating flows. Motivated by novel applications in electro-conductive microchannel transport systems, the current article investigates analyti...
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Zeeshan Khan
2017-05-01
Full Text Available Wire coating process is a continuous extrusion process for primary insulation of conducting wires with molten polymers for mechanical strength and protection in aggressive environments. Nylon, polysulfide, low/high density polyethylene (LDPE/HDPE and plastic polyvinyl chloride (PVC are the common and important plastic resin used for wire coating. In the current study, wire coating is performed using viscoelastic third grade fluid in the presence of applied magnetic field and porous medium. The governing equations are first modeled and then solved analytically by utilizing the homotopy analysis method (HAM. The convergence of the series solution is established. A numerical technique called ND-solve method is used for comparison and found good agreement. The effect of pertinent parameters on the velocity field and temperature profile is shown with the help of graphs. It is observed that the velocity profiles increase as the value of viscoelastic third grade parameter β increase and decrease as the magnetic parameter M and permeability parameter K increase. It is also observed that the temperature profiles increases as the Brinkman number B r , permeability parameter K , magnetic parameter M and viscoelastic third grade parameter (non-Newtonian parameter β increase.
Riggins, David W.
2002-01-01
The performance of the MHD energy bypass air-breathing engine for high-speed propulsion is analyzed in this investigation. This engine is a specific type of the general class of inverse cycle engines. In this paper, the general relationship between engine performance (specific impulse and specific thrust) and the overall total pressure ratio through an engine (from inlet plane to exit plane) is first developed and illustrated. Engines with large total pressure decreases, regardless of cause or source, are seen to have exponentially decreasing performance. The ideal inverse cycle engine (of which the MHD engine is a sub-set) is then demonstrated to have a significant total pressure decrease across the engine; this total pressure decrease is cycle-driven, degrades rapidly with energy bypass ratio, and is independent of any irreversibility. The ideal MHD engine (inverse cycle engine with no irreversibility other than that inherent in the MHD work interaction processes) is next examined and is seen to have an additional large total pressure decrease due to MHD-generated irreversibility in the decelerator and the accelerator. This irreversibility mainly occurs in the deceleration process. Both inherent total pressure losses (inverse cycle and MHD irreversibility) result in a significant narrowing of the performance capability of the MHD bypass engine. The fundamental characteristics of MHD flow acceleration and flow deceleration from the standpoint of irreversibility and second-law constraints are next examined in order to clarify issues regarding flow losses and parameter selection in the MM modules. Severe constraints are seen to exist in the decelerator in terms of allowable deceleration Mach numbers and volumetric (length) required for meaningful energy bypass (work interaction). Considerable difficulties are also encountered and discussed due to thermal/work choking phenomena associated with the deceleration process. Lastly, full engine simulations utilizing inlet shock systems, finite-rate chemistry, wall cooling with thermally balanced engine (fuel heat sink), fuel injection and mixing, friction, etc. are shown and discussed for both the MHD engine and the conventional scramjet. The MHD bypass engine has significantly lower performance in all categories across the Mach number range (8 to 12.2). The lower performance is attributed to the combined effects of 1) additional irreversibility and cooling requirements associated with the MHD components and 2) the total pressure decrease associated with the inverse cycle itself.
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Meng Zhi-Jun
2016-01-01
Full Text Available This paper addresses the systems of the incompressible Navier-Stokes equations on Cantor sets without the external force involving the fractal heat-conduction problem vial local fractional derivative. The spherical Cantor type co-ordinate method is used to transfer the incompressible Navier-Stokes equation from the Cantorian co-ordinate system into the spherical Cantor type co-ordinate system.
Numerical algorithms for steady and unsteady incompressible Navier-Stokes equations
Hafez, Mohammed; Dacles, Jennifer
1989-01-01
The numerical analysis of the incompressible Navier-Stokes equations are becoming important tools in the understanding of some fluid flow problems which are encountered in research as well as in industry. With the advent of the supercomputers, more realistic problems can be studied with a wider choice of numerical algorithms. An alternative formulation is presented for viscous incompressible flows. The incompressible Navier-Stokes equations are cast in a velocity/vorticity formulation. This formulation consists of solving the Poisson equations for the velocity components and the vorticity transport equation. Two numerical algorithms for the steady two-dimensional laminar flows are presented. The first method is based on the actual partial differential equations. This uses a finite-difference approximation of the governing equations on a staggered grid. The second method uses a finite element discretization with the vorticity transport equation approximated using a Galerkin approximation and the Poisson equations are obtained using a least squares method. The equations are solved efficiently using Newton's method and a banded direct matrix solver (LINPACK). The method is extended to steady three-dimensional laminar flows and applied to a cubic driven cavity using finite difference schemes and a staggered grid arrangement on a Cartesian mesh. The equations are solved iteratively using a plane zebra relaxation scheme. Currently, a two-dimensional, unsteady algorithm is being developed using a generalized coordinate system. The equations are discretized using a finite-volume approach. This work will then be extended to three-dimensional flows.
Musharbash, Eleonora; Nobile, Fabio
2018-02-01
In this paper we propose a method for the strong imposition of random Dirichlet boundary conditions in the Dynamical Low Rank (DLR) approximation of parabolic PDEs and, in particular, incompressible Navier Stokes equations. We show that the DLR variational principle can be set in the constrained manifold of all S rank random fields with a prescribed value on the boundary, expressed in low rank format, with rank smaller then S. We characterize the tangent space to the constrained manifold by means of a Dual Dynamically Orthogonal (Dual DO) formulation, in which the stochastic modes are kept orthonormal and the deterministic modes satisfy suitable boundary conditions, consistent with the original problem. The Dual DO formulation is also convenient to include the incompressibility constraint, when dealing with incompressible Navier Stokes equations. We show the performance of the proposed Dual DO approximation on two numerical test cases: the classical benchmark of a laminar flow around a cylinder with random inflow velocity, and a biomedical application for simulating blood flow in realistic carotid artery reconstructed from MRI data with random inflow conditions coming from Doppler measurements.
Energy Technology Data Exchange (ETDEWEB)
Jobelin, M
2006-10-15
This thesis treats of time resolution methods for the Navier-Stokes equations. Based on the well-known projection method of Chorin and Temam, an original pressure correction method, named 'projection-penalty' is developed. Its specificity concerns the addition of a penalty term in the prediction step, which constrains the predicted velocity to fit with the mass balance. The precision improvements added by this method are demonstrated by some analysis results and by some numerical experiments of incompressible or dilatable flows. Finally, the potentialities offered by the use of the joint finite elements method in this type of fractionary step scheme is studied. Two applications are presented, one for local refinement purpose, the other for the resolution of a multi-physics problem. (J.S.)
Cauchy Problem for Dissipative Hölder Solutions to the Incompressible Euler Equations
Daneri, S.
2014-07-01
We consider solutions to the Cauchy problem for the incompressible Euler equations on the 3-dimensional torus which are continuous or Hölder continuous for any exponent . Using the techniques introduced in De Lellis and Székelyhidi (Inventiones Mathematicae 9:377-407, 2013; Dissipative Euler flows and Onsager's conjecture, 2012), we prove the existence of infinitely many (Hölder) continuous initial vector fields starting from which there exist infinitely many (Hölder) continuous solutions with preassigned total kinetic energy.
CABARET scheme in velocity-pressure formulation for two-dimensional incompressible fluids
Glotov, V. Yu.; Goloviznin, V. M.
2013-06-01
The CABARET method was generalized to two-dimensional incompressible fluids in terms of velocity and pressure. The resulting algorithm was verified by computing the transport and interaction of various vortex structures: a stationary and a moving solitary vortex, Taylor-Green vortices, and vortices formed by the instability of double shear layers. Much attention was also given to the modeling of homogeneous isotropic turbulence and to the analysis of its spectral properties. It was shown that, regardless of the mesh size, the slope of the energy spectra up to the highest-frequency harmonics is equal -3, which agrees with Batchelor's enstrophy cascade theory.
An exact solution to the draining reservoir problem of the incompressible and non-viscous liquid
Energy Technology Data Exchange (ETDEWEB)
Hong, Seok-In [Department of Science Education, Gyeongin National University of Education, Anyang 430-739 (Korea, Republic of)], E-mail: sihongtao@hanmail.net
2009-03-15
The exact expressions for the drain time and the height, velocity and acceleration of the free surface are found for the draining reservoir problem of the incompressible and non-viscous liquid. Contrary to the conventional approximate results, they correctly describe the initial time dependence of the liquid velocity and acceleration. Torricelli's law does not hold in the initial transient region, which imposes restrictions on the validity of the analogy between the drain system and the electric circuit (Ohm's law)
Directory of Open Access Journals (Sweden)
Rezanova Ekaterina
2017-01-01
Full Text Available The dynamics of a viscous incompressible liquid layer and the temperature distribution in it are investigated numerically in three-dimensional case. The planar layer with free boundaries under condition of zero gravity is studied on the basis of the special class of exact solutions of the Navier-Stokes equations. The thermocapillary forces and additional tangential stresses on the boundaries caused by the environment are taken into account. The influence of additional tangential stresses on the layer dynamics and heat distribution is studied.
Application of the Krylov subspace method to the incompressible navier-stokes equations
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Maeng, J.S. [Hanyang University, Seoul (Korea); Choi, I.K.; Lim, Y.W. [Hanyang University Graduate School, Seoul(Korea)
2000-07-01
The preconditioned Krylov subspace methods were applied to the incompressible Navier-Stoke's equations for convergence acceleration. Three of the Krylov subspace methods combined with the five of the preconditioners were tested to solve the lid-driven cavity flow problem. The MILU preconditioned CG method showed very fast and stable convergency. The combination of GMRES/MILU-CG solver for momentum and pressure correction equations was found less dependency on the number of the grid points among them. A guide line for stopping inner iterations for each equation is offered. (author). 18 refs., 4 figs., 6 tabs.
Application of a fractional-step method to incompressible Navier-Stokes equations
Kim, J.; Moin, P.
1985-01-01
A numerical method for computing three dimensional, time dependent incompressible flows is presented. The method is based on a fractional step, or time-splitting, scheme in conjunction with the approximate-factorization technique. The use of velocity boundary conditions for the intermediate velocity field leads to inconsistent numerical solutions. Appropriate boundary conditions for the intermediate velocity field are derived and tested. Numerical solutions for flow inside a driven cavity and over a backward-facing step are presented and compared with experimental data and other numerical results.
Application of a fractional-step method to incompressible Navier-Stokes equation
Kim, J.; Moin, P.
1984-01-01
A numerical method for computing three dimensional, time dependent incompressible flows is presented. The method is based on a fractional step, or time-splitting, scheme in conjunction with the approximate-factorization technique. The use of velocity boundary conditions for the intermediate velocity field leads to inconsistent numerical solutions. Appropriate boundary conditions for the intermediate velocity field are derived and tested. Numerical solutions for flow inside a driven cavity and over a backward-facing step are presented and compared with experimenal data and other numerical results.
Incompressible viscous flow computations for the pump components and the artificial heart
Kiris, Cetin
1992-01-01
A finite difference, three dimensional incompressible Navier-Stokes formulation to calculate the flow through turbopump components is utilized. The solution method is based on the pseudo compressibility approach and uses an implicit upwind differencing scheme together with the Gauss-Seidel line relaxation method. Both steady and unsteady flow calculations can be performed using the current algorithm. Here, equations are solved in steadily rotating reference frames by using the steady state formulation in order to simulate the flow through a turbopump inducer. Eddy viscosity is computed by using an algebraic mixing-length turbulence model. Numerical results are compared with experimental measurements and a good agreement is found between the two.
An Equal-Order DG Method for the Incompressible Navier-Stokes Equations
Cockburn, Bernardo
2008-12-20
We introduce and analyze a discontinuous Galerkin method for the incompressible Navier-Stokes equations that is based on finite element spaces of the same polynomial order for the approximation of the velocity and the pressure. Stability of this equal-order approach is ensured by a pressure stabilization term. A simple element-by-element post-processing procedure is used to provide globally divergence-free velocity approximations. For small data, we prove the existence and uniqueness of discrete solutions and carry out an error analysis of the method. A series of numerical results are presented that validate our theoretical findings. © 2008 Springer Science+Business Media, LLC.
A least-squares finite element method for incompressible Navier-Stokes problems
Jiang, Bo-Nan
1989-01-01
A least-squares finite element method, based on the velocity-pressure-vorticity formulation, is developed for solving steady incompressible Navier-Stokes problems. This method leads to a minimization problem rather than to a saddle-point problem by the classic mixed method, and can thus accommodate equal-order interpolations. This method has no parameter to tune. The associated algebraic system is symmetric, and positive definite. Numerical results for the cavity flow at Reynolds number up to 10,000 and the backward-facing step flow at Reynolds number up to 900 are presented.
Solutions to three-dimensional Navier-Stokes equations for incompressible fluids
Directory of Open Access Journals (Sweden)
Jorma Jormakka
2010-07-01
Full Text Available This article gives explicit solutions to the space-periodic Navier-Stokes problem with non-periodic pressure. These type of solutions are not unique and by using such solutions one can construct a periodic, smooth, divergence-free initial vector field allowing a space-periodic and time-bounded external force such that there exists a smooth solution to the 3-dimensional Navier-Stokes equations for incompressible fluid with those initial conditions, but the solution cannot be continued to the whole space.
An Operator-Integration-Factor Splitting (OIFS) method for Incompressible Flows in Moving Domains
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Patel, Saumil S. [Argonne National Lab. (ANL), Argonne, IL (United States); Fischer, Paul F. [Argonne National Lab. (ANL), Argonne, IL (United States); Univ. of Illinois, Urbana-Champaign, IL (United States); Min, Misun [Argonne National Lab. (ANL), Argonne, IL (United States); Tomboulides, Ananias G [Argonne National Lab. (ANL), Argonne, IL (United States); Aristotle Univ., Thessaloniki (Greece)
2017-10-21
In this paper, we present a characteristic-based numerical procedure for simulating incompressible flows in domains with moving boundaries. Our approach utilizes an operator-integration-factor splitting technique to help produce an effcient and stable numerical scheme. Using the spectral element method and an arbitrary Lagrangian-Eulerian formulation, we investigate flows where the convective acceleration effects are non-negligible. Several examples, ranging from laminar to turbulent flows, are considered. Comparisons with a standard, semi-implicit time-stepping procedure illustrate the improved performance of the scheme.
Incompressible Steady Flow with Tensor Conductivity Leaving a Transverse Magnetic Field
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Witalis, E.A.
1965-12-15
The straight channel flow of an inviscid, incompressible fluid with tensor conductivity is considered when the flow leaves a region of constant transverse magnetic field. The channel walls are taken to be insulating, and an eddy current system arises. This is investigated by the method of magnetic field analysis as given by Witalis. The spatial distribution of magnetic field and ohmic power loss, both parallel and transverse to the flow, are given as functions of the Hall parameter with consideration also to the magnetic Reynolds number of the fluid. MHD power generator aspects of this problem and the results are discussed.
Gradient-augmented hybrid interface capturing method for incompressible two-phase flow
Zheng, Fu; Shi-Yu, Wu; Kai-Xin, Liu
2016-06-01
Motivated by inconveniences of present hybrid methods, a gradient-augmented hybrid interface capturing method (GAHM) is presented for incompressible two-phase flow. A front tracking method (FTM) is used as the skeleton of the GAHM for low mass loss and resources. Smooth eulerian level set values are calculated from the FTM interface, and are used for a local interface reconstruction. The reconstruction avoids marker particle redistribution and enables an automatic treatment of interfacial topology change. The cubic Hermit interpolation is employed in all steps of the GAHM to capture subgrid structures within a single spacial cell. The performance of the GAHM is carefully evaluated in a benchmark test. Results show significant improvements of mass loss, clear subgrid structures, highly accurate derivatives (normals and curvatures) and low cost. The GAHM is further coupled with an incompressible multiphase flow solver, Super CE/SE, for more complex and practical applications. The updated solver is evaluated through comparison with an early droplet research. Project supported by the National Natural Science Foundation of China (Grant Nos. 10972010, 11028206, 11371069, 11372052, 11402029, and 11472060), the Science and Technology Development Foundation of China Academy of Engineering Physics (CAEP), China (Grant No. 2014B0201030), and the Defense Industrial Technology Development Program of China (Grant No. B1520132012).
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Gjesdal, Thor
1997-12-31
This thesis discusses the development and application of efficient numerical methods for the simulation of fluid flows, in particular the flow of incompressible fluids. The emphasis is on practical aspects of algorithm development and on application of the methods either to linear scalar model equations or to the non-linear incompressible Navier-Stokes equations. The first part deals with cell centred multigrid methods and linear correction scheme and presents papers on (1) generalization of the method to arbitrary sized grids for diffusion problems, (2) low order method for advection-diffusion problems, (3) attempt to extend the basic method to advection-diffusion problems, (4) Fourier smoothing analysis of multicolour relaxation schemes, and (5) analysis of high-order discretizations for advection terms. The second part discusses a multigrid based on pressure correction methods, non-linear full approximation scheme, and papers on (1) systematic comparison of the performance of different pressure correction smoothers and some other algorithmic variants, low to moderate Reynolds numbers, and (2) systematic study of implementation strategies for high order advection schemes, high-Re flow. An appendix contains Fortran 90 data structures for multigrid development. 160 refs., 26 figs., 22 tabs.
The most incompressible metal osmium at static pressures above 750 gigapascals
Dubrovinsky, L.; Dubrovinskaia, N.; Bykova, E.; Bykov, M.; Prakapenka, V.; Prescher, C.; Glazyrin, K.; Liermann, H.-P.; Hanfland, M.; Ekholm, M.; Feng, Q.; Pourovskii, L. V.; Katsnelson, M. I.; Wills, J. M.; Abrikosov, I. A.
2015-09-01
Metallic osmium (Os) is one of the most exceptional elemental materials, having, at ambient pressure, the highest known density and one of the highest cohesive energies and melting temperatures. It is also very incompressible, but its high-pressure behaviour is not well understood because it has been studied so far only at pressures below 75 gigapascals. Here we report powder X-ray diffraction measurements on Os at multi-megabar pressures using both conventional and double-stage diamond anvil cells, with accurate pressure determination ensured by first obtaining self-consistent equations of state of gold, platinum, and tungsten in static experiments up to 500 gigapascals. These measurements allow us to show that Os retains its hexagonal close-packed structure upon compression to over 770 gigapascals. But although its molar volume monotonically decreases with pressure, the unit cell parameter ratio of Os exhibits anomalies at approximately 150 gigapascals and 440 gigapascals. Dynamical mean-field theory calculations suggest that the former anomaly is a signature of the topological change of the Fermi surface for valence electrons. However, the anomaly at 440 gigapascals might be related to an electronic transition associated with pressure-induced interactions between core electrons. The ability to affect the core electrons under static high-pressure experimental conditions, even for incompressible metals such as Os, opens up opportunities to search for new states of matter under extreme compression.
Incompressible Turbulent Flow Simulation Using the κ-ɛ Model and Upwind Schemes
Directory of Open Access Journals (Sweden)
V. G. Ferreira
2007-01-01
Full Text Available In the computation of turbulent flows via turbulence modeling, the treatment of the convective terms is a key issue. In the present work, we present a numerical technique for simulating two-dimensional incompressible turbulent flows. In particular, the performance of the high Reynolds κ-ɛ model and a new high-order upwind scheme (adaptative QUICKEST by Kaibara et al. (2005 is assessed for 2D confined and free-surface incompressible turbulent flows. The model equations are solved with the fractional-step projection method in primitive variables. Solutions are obtained by using an adaptation of the front tracking GENSMAC (Tomé and McKee (1994 methodology for calculating fluid flows at high Reynolds numbers. The calculations are performed by using the 2D version of the Freeflow simulation system (Castello et al. (2000. A specific way of implementing wall functions is also tested and assessed. The numerical procedure is tested by solving three fluid flow problems, namely, turbulent flow over a backward-facing step, turbulent boundary layer over a flat plate under zero-pressure gradients, and a turbulent free jet impinging onto a flat surface. The numerical method is then applied to solve the flow of a horizontal jet penetrating a quiescent fluid from an entry port beneath the free surface.
An adaptive level set approach for incompressible two-phase flows
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Sussman, M.; Almgren, A.S.; Bell, J.B. [and others
1997-04-01
In Sussman, Smereka and Osher, a numerical method using the level set approach was formulated for solving incompressible two-phase flow with surface tension. In the level set approach, the interface is represented as the zero level set of a smooth function; this has the effect of replacing the advection of density, which has steep gradients at the interface, with the advection of the level set function, which is smooth. In addition, the interface can merge or break up with no special treatment. The authors maintain the level set function as the signed distance from the interface in order to robustly compute flows with high density ratios and stiff surface tension effects. In this work, they couple the level set scheme to an adaptive projection method for the incompressible Navier-Stokes equations, in order to achieve higher resolution of the interface with a minimum of additional expense. They present two-dimensional axisymmetric and fully three-dimensional results of air bubble and water drop computations.
Pan, Ronghua; Zhou, Yi; Zhu, Yi
2018-02-01
In this paper, we study the global existence of classical solutions to the three dimensional incompressible viscous magneto-hydrodynamical system without magnetic diffusion on periodic boxes, that is, with periodic boundary conditions. We work in Eulerian coordinates and employ a time-weighted energy estimate to prove the global existence result, under the assumptions that the initial magnetic field is close enough to an equilibrium state and the initial data have some symmetries.
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Choudhary, Aniruddha
Code verifition is the process of ensuring, to the degree possible, that there are no algorithm deficiencies and coding mistakes (bugs) in a scientific computing simulation. In this work, techniques are presented for performing code verifition of boundary conditions commonly used in compressible and incompressible Computational Fluid Dynamics (CFD) codes. Using a compressible CFD code, this study assesses the subsonic in flow (isentropic and fixed-mass), subsonic out ow, supersonic out ow, no-slip wall (adiabatic and isothermal), and inviscid slip-wall. The use of simplified curved surfaces is proposed for easier generation of manufactured solutions during the verifition of certain boundary conditions involving many constraints. To perform rigorous code verifition, general grids with mixed cell types at the verified boundary are used. A novel approach is introduced to determine manufactured solutions for boundary condition verifition when the velocity-field is constrained to be divergence-free during the simulation in an incompressible CFD code. Order of accuracy testing using the Method of Manufactured Solutions (MMS) is employed here for code verifition of the major components of an open-source, multiphase ow code - MFIX. The presence of two-phase governing equations and a modified SIMPLE-based algorithm requiring divergence-free flows makes the selection of manufactured solutions more involved than for single-phase, compressible flows. Code verifition is performed here on 2D and 3D, uniform and stretched meshes for incompressible, steady and unsteady, single-phase and two-phase flows using the two-fluid model of MFIX. In a CFD simulation, truncation error (TE) is the difference between the continuous governing equation and its discrete approximation. Since TE can be shown to be the local source term for the discretization error, TE is proposed as the criterion for determining which regions of the computational mesh should be refined/coarsened. For mesh
Kwon, Young-Sam
2017-12-01
The flow of chemically reacting gaseous mixture is associated with a variety of phenomena and processes. We study the combined quasineutral and inviscid limit from the flow of chemically reacting gaseous mixture governed by Poisson equation to incompressible Euler equations with the ill-prepared initial data in the unbounded domain R^2× T. Furthermore, the convergence rates are obtained.
Choudhury, Anupam Pal; Crippa, Gianluca; Spinolo, Laura V.
2017-12-01
We establish existence and uniqueness results for initial-boundary value problems with nearly incompressible vector fields. We then apply our results to establish well-posedness of the initial-boundary value problem for the Keyfitz and Kranzer system of conservation laws in several space dimensions.
Cebeci, Tuncer
2005-01-01
This second edition of our book extends the modeling and calculation of boundary-layer flows to include compressible flows. The subjects cover laminar, transitional and turbulent boundary layers for two- and three-dimensional incompressible and compressible flows. The viscous-inviscid coupling between the boundary layer and the inviscid flow is also addressed. The book has a large number of homework problems.
Energy Technology Data Exchange (ETDEWEB)
Garcia, Jr., W. J.; Viecelli, J. A.
1976-06-01
This report is intended to be a ''user manual'' for the Lawrence Livermore Laboratory version of the Eulerian incompressible hydrodynamic computer code ABMAC. The theory of the numerical model is discussed in general terms. The format for data input and data printout is described in detail. A listing and flow chart of the computer code are provided.
Li, T; Liu, Y; Marks, R; Nayak, B K; Rao, P V Madhusudhana; Fujiwara, M; Hashimoto, H; Kawase, K; Nakanishi, K; Okumura, S; Yosoi, M; Itoh, M; Ichikawa, M; Matsuo, R; Terazano, T; Uchida, M; Kawabata, T; Akimune, H; Iwao, Y; Murakami, T; Sakaguchi, H; Terashima, S; Yasuda, Y; Zenihiro, J; Harakeh, M N
2007-01-01
We have investigated the isoscalar giant monopole resonance (GMR) in the Sn isotopes, using inelastic scattering of 400-MeV $\\alpha$-particles at extremely forward angles, including 0 deg. A value of -550 \\pm 100 MeV has been obtained for the asymmetry term, $K_\\tau$, in the nuclear incompressibility.
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John, V.; Matthies, G.; Tobiska, L. [Magdeburg Univ. (Germany). Inst. fuer Analysis und Numerik
2001-07-01
For solving complex three-dimensional flow problems, many different approaches have been developed. It turns out that both the discretization concept and the solver designed for the discrete problem influences essentially the accuracy and efficiency of the method. The main objective of the paper is to compare lower and higher order finite element discretizations for the accurate and fast solution of the incompressible Navier-Stokes equation in three space dimensions. To this end, a well-defined benchmark problem of a channel flow around an obstacle is used to quantify the gain in accuracy when higher order discretizations are used. The comparison covers also the robust and efficient solution of the discretized algebraic equations. (orig.)
Self-organization of two-dimensional incompressible viscous flow in a friction-free box
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Kondoh, Y.; Yoshizawa, M.; Nakano, A. [Gunma Univ., Kiryu (Japan). Faculty of Engineering; Yabe, T.
1995-10-01
The process by which self-organization occurs for two-dimensional incompressible viscous flow in a friction-free box is investigated theoretically with the use of numerical simulations. It is shown by an eigenfunction spectrum analysis that two basic processes for the self-organization are the spectrum transfer by nonlinear couplings and the selective dissipation among the eigenmodes of the dissipative operator, and they yield spectrum accumulation at the lowest eigenmode. It is also clarified that an important process during nonlinear self-organization is an interchange between the dominant operators, which leads to a final self-similar coherent structure, determined uniquely by the lowest eigenmode of the dissipative operator. (author).
Swimming of a deformable slab in a viscous incompressible fluid with inertia
Felderhof, B U
2015-01-01
The swimming of a deformable planar slab in a viscous incompressible fluid is studied on the basis of the Navier-Stokes equations. A continuum of plane wave displacements, symmetric on both sides of the slab and characterized by a polarization angle, allows optimization of the swimming efficiency with respect to polarization. The mean swimming velocity and mean rate of dissipation are calculated to second order in the amplitude of the stroke. The optimum efficiency depends on the ratio of viscosity and mass density of the fluid. For high viscosity a stroke is found with significantly higher efficiency than Taylor's solution for a swimming sheet. For low viscosity the efficiency is optimal for a nearly irrotational flow pattern.
A multiple pass space-marching method for three-dimensional incompressible viscous flow
Kirtley, K. R.; Lakshminarayana, B.
A new multiple pass space-marching method for the coupled three-dimensional form of the incompressible, partially parabolized Navier-Stokes equation is developed. Pseudocompressibility theory is incorporated to give a stable and convergent algorithm for internal flow computations. The effect of initial conditions, mesh size and the pseudocompressibility coefficient on stability and convergence of the method is studied. Also studied is the influence of the factorization error inherent in the linearized block implicit solution procedure. The accuracy of the method is assessed by computing the developing laminar flow in a square straight duct; comparisons with analysis are very good. In addition, the computation of the developing laminar flow in an S-shaped duct yields results in good agreement with the experimental data.
A Split-Step Scheme for the Incompressible Navier-Stokes
Energy Technology Data Exchange (ETDEWEB)
Henshaw, W; Petersson, N A
2001-06-12
We describe a split-step finite-difference scheme for solving the incompressible Navier-Stokes equations on composite overlapping grids. The split-step approach decouples the solution of the velocity variables from the solution of the pressure. The scheme is based on the velocity-pressure formulation and uses a method of lines approach so that a variety of implicit or explicit time stepping schemes can be used once the equations have been discretized in space. We have implemented both second-order and fourth-order accurate spatial approximations that can be used with implicit or explicit time stepping methods. We describe how to choose appropriate boundary conditions to make the scheme accurate and stable. A divergence damping term is added to the pressure equation to keep the numerical dilatation small. Several numerical examples are presented.
Symmetry Analysis and Exact Solutions of the 2D Unsteady Incompressible Boundary-Layer Equations
Han, Zhong; Chen, Yong
2017-01-01
To find intrinsically different symmetry reductions and inequivalent group invariant solutions of the 2D unsteady incompressible boundary-layer equations, a two-dimensional optimal system is constructed which attributed to the classification of the corresponding Lie subalgebras. The comprehensiveness and inequivalence of the optimal system are shown clearly under different values of invariants. Then by virtue of the optimal system obtained, the boundary-layer equations are directly reduced to a system of ordinary differential equations (ODEs) by only one step. It has been shown that not only do we recover many of the known results but also find some new reductions and explicit solutions, which may be previously unknown. Supported by the Global Change Research Program of China under Grant No. 2015CB953904, National Natural Science Foundation of China under Grant Nos. 11275072, 11435005, 11675054, and Shanghai Collaborative Innovation Center of Trustworthy Software for Internet of Things under Grant No. ZF1213
Simulation of Free Airfoil Vibrations in Incompressible Viscous Flow — Comparison of FEM and FVM
Directory of Open Access Journals (Sweden)
Petr Sváček
2012-01-01
Full Text Available This paper deals with a numerical solution of the interaction of two-dimensional (2-D incompressible viscous flow and a vibrating profile NACA 0012 with large amplitudes. The laminar flow is described by the Navier-Stokes equations in the arbitrary Lagrangian-Eulerian form. The profile with two degrees of freedom (2-DOF can rotate around its elastic axis and oscillate in the vertical direction. Its motion is described by a nonlinear system of two ordinary differential equations. Deformations of the computational domain due to the profile motion are treated by the arbitrary Lagrangian-Eulerianmethod. The finite volume method and the finite element method are applied, and the numerical results are compared.
A high-resolution code for large eddy simulation of incompressible turbulent boundary layer flows
Cheng, Wan
2014-03-01
We describe a framework for large eddy simulation (LES) of incompressible turbulent boundary layers over a flat plate. This framework uses a fractional-step method with fourth-order finite difference on a staggered mesh. We present several laminar examples to establish the fourth-order accuracy and energy conservation property of the code. Furthermore, we implement a recycling method to generate turbulent inflow. We use the stretched spiral vortex subgrid-scale model and virtual wall model to simulate the turbulent boundary layer flow. We find that the case with Reθ ≈ 2.5 × 105 agrees well with available experimental measurements of wall friction, streamwise velocity profiles and turbulent intensities. We demonstrate that for cases with extremely large Reynolds numbers (Reθ = 1012), the present LES can reasonably predict the flow with a coarse mesh. The parallel implementation of the LES code demonstrates reasonable scaling on O(103) cores. © 2013 Elsevier Ltd.
Lagrange–Galerkin methods for the incompressible Navier-Stokes equations: a review
Directory of Open Access Journals (Sweden)
Bermejo Rodolfo
2016-09-01
Full Text Available We review in this paper the development of Lagrange-Galerkin (LG methods to integrate the incompressible Navier-Stokes equations (NSEs for engineering applications. These methods were introduced in the computational fluid dynamics community in the early eighties of the past century, and at that time they were considered good methods for both their theoretical stability properties and the way of dealing with the nonlinear terms of the equations; however, the numerical experience gained with the application of LG methods to different problems has identified drawbacks of them, such as the calculation of specific integrals that arise in their formulation and the calculation of the ow trajectories, which somehow have hampered the applicability of LG methods. In this paper, we focus on these issues and summarize the convergence results of LG methods; furthermore, we shall briefly introduce a new stabilized LG method suitable for high Reynolds numbers.
Mohamed, Mamdouh S; Samtaney, Ravi
2015-01-01
A conservative discretization of incompressible Navier-Stokes equations on simplicial meshes is developed based on discrete exterior calculus (DEC). A distinguishing feature of our method is the use of an algebraic discretization of the contraction operator and a combinatorial discretization of the wedge product. The governing equations are first rewritten using the exterior calculus notation, replacing vector calculus differential operators by the exterior derivative, Hodge star and wedge product operators. The discretization is then carried out by substituting with the corresponding discrete operators based on the DEC framework. Numerical experiments reveal a second order accuracy for the developed scheme when using structured-triangular meshes, and first order accuracy for otherwise unstructured meshes. By construction, the method is conservative in that both mass and vorticity are conserved up to machine precision. The relative error in kinetic energy for inviscid flow test cases converges in a second ord...
Kou, Jisheng
2013-01-01
A class of discontinuous Galerkin methods with interior penalties is presented for incompressible two-phase flow in heterogeneous porous media with capillary pressures. The semidiscrete approximate schemes for fully coupled system of two-phase flow are formulated. In highly heterogeneous permeable media, the saturation is discontinuous due to different capillary pressures, and therefore, the proposed methods incorporate the capillary pressures in the pressure equation instead of saturation equation. By introducing a coupling approach for stability and error estimates instead of the conventional separate analysis for pressure and saturation, the stability of the schemes in space and time and a priori hp error estimates are presented in the L2(H 1) for pressure and in the L∞(L2) and L2(H1) for saturation. Two time discretization schemes are introduced for effectively computing the discrete solutions. © 2013 Societ y for Industrial and Applied Mathematics.
Tamellini, L.
2014-01-01
In this paper we consider a proper generalized decomposition method to solve the steady incompressible Navier-Stokes equations with random Reynolds number and forcing term. The aim of such a technique is to compute a low-cost reduced basis approximation of the full stochastic Galerkin solution of the problem at hand. A particular algorithm, inspired by the Arnoldi method for solving eigenproblems, is proposed for an efficient greedy construction of a deterministic reduced basis approximation. This algorithm decouples the computation of the deterministic and stochastic components of the solution, thus allowing reuse of preexisting deterministic Navier-Stokes solvers. It has the remarkable property of only requiring the solution of m uncoupled deterministic problems for the construction of an m-dimensional reduced basis rather than M coupled problems of the full stochastic Galerkin approximation space, with m l M (up to one order of magnitudefor the problem at hand in this work). © 2014 Society for Industrial and Applied Mathematics.
Kiris, Cetin; Kwak, Dochan
1995-01-01
The fractional step and the pseudocompressibility methods for the solution of the incompressible Navier-Stokes equations are outlined. The fractional step method is based on finite-volume formulation and uses the pressure and the volume fluxes across the faces of each cell as dependent variables. The momentum equations are solved implicitly and the Poisson equation for the pressure is solved by using the multigrid method. The pseudocompressibility approach uses an implicit-higher-order-upwind differencing scheme for the convective terms together with the Gauss-Seidel line relaxation method. The dependent variables in the pseudocompressibility approach are the pressure and the cartesian velocity components in unstaggered mesh orientation. The 90-degree square duct flow, the wing-tip vortex wake flow and unsteady turbulent flows over an oscillating NACA 0015 airfoil are computed using both the fractional step and the pseudocompressibility methods. The results obtained from two different schemes are compared against experimental measurements.
Level Set Projection Method for Incompressible Navier-Stokes on Arbitrary Boundaries
Williams-Rioux, Bertrand
2012-01-12
Second order level set projection method for incompressible Navier-Stokes equations is proposed to solve flow around arbitrary geometries. We used rectilinear grid with collocated cell centered velocity and pressure. An explicit Godunov procedure is used to address the nonlinear advection terms, and an implicit Crank-Nicholson method to update viscous effects. An approximate pressure projection is implemented at the end of the time stepping using multigrid as a conventional fast iterative method. The level set method developed by Osher and Sethian [17] is implemented to address real momentum and pressure boundary conditions by the advection of a distance function, as proposed by Aslam [3]. Numerical results for the Strouhal number and drag coefficients validated the model with good accuracy for flow over a cylinder in the parallel shedding regime (47 < Re < 180). Simulations for an array of cylinders and an oscillating cylinder were performed, with the latter demonstrating our methods ability to handle dynamic boundary conditions.
POD-Galerkin Model for Incompressible Single-Phase Flow in Porous Media
Wang, Yi
2017-01-25
Fast prediction modeling via proper orthogonal decomposition method combined with Galerkin projection is applied to incompressible single-phase fluid flow in porous media. Cases for different configurations of porous media, boundary conditions and problem scales are designed to examine the fidelity and robustness of the model. High precision (relative deviation 1.0 x 10(-4)% similar to 2.3 x 10(-1)%) and large acceleration (speed-up 880 similar to 98454 times) of POD model are found in these cases. Moreover, the computational time of POD model is quite insensitive to the complexity of problems. These results indicate POD model is especially suitable for large-scale complex problems in engineering.
A Rotational Pressure-Correction Scheme for Incompressible Two-Phase Flows with Open Boundaries.
Directory of Open Access Journals (Sweden)
S Dong
Full Text Available Two-phase outflows refer to situations where the interface formed between two immiscible incompressible fluids passes through open portions of the domain boundary. We present several new forms of open boundary conditions for two-phase outflow simulations within the phase field framework, as well as a rotational pressure correction based algorithm for numerically treating these open boundary conditions. Our algorithm gives rise to linear algebraic systems for the velocity and the pressure that involve only constant and time-independent coefficient matrices after discretization, despite the variable density and variable viscosity of the two-phase mixture. By comparing simulation results with theory and the experimental data, we show that the method produces physically accurate results. We also present numerical experiments to demonstrate the long-term stability of the method in situations where large density contrast, large viscosity contrast, and backflows occur at the two-phase open boundaries.
An adaptive levelset method for computing solutions to incompressible two-phase flows.
Sussman, Mark; Lbnl Collaboration; Fatemi, Emad; Smereka, Peter; Osher, Stan
1997-11-01
We present an adaptive level set method for computing 2d axisymmetric and fully 3d incompressible two-phase flow. Our methodology is specifically targeted at problems characterized by large density and viscosity jumps (e.g. air/water) and stiff, singular source terms, such as those due to surface tension. One such application is the modeling of ink-jet printers in which one wants to accurately model the break-up of the jet into droplets. We compare our method to the Volume-of-Fluid method and the Boundary Integral Method; we focus our comparison to problems in which a change in topology occurs. We also validate our method against experiments and theory.
Swimming of a sphere in a viscous incompressible fluid with inertia
Felderhof, B. U.; Jones, R. B.
2017-08-01
The swimming of a sphere immersed in a viscous incompressible fluid with inertia is studied for surface modulations of small amplitude on the basis of the Navier-Stokes equations. The mean swimming velocity and the mean rate of dissipation are expressed as quadratic forms in term of the surface displacements. With a choice of a basis set of modes the quadratic forms correspond to two Hermitian matrices. Optimization of the mean swimming velocity for given rate of dissipation requires the solution of a generalized eigenvalue problem involving the two matrices. It is found for surface modulations of low multipole order that the optimal swimming efficiency depends in intricate fashion on a dimensionless scale number involving the radius of the sphere, the period of the cycle, and the kinematic viscosity of the fluid.
Mohamed, Mamdouh S.
2016-02-11
A conservative discretization of incompressible Navier–Stokes equations is developed based on discrete exterior calculus (DEC). A distinguishing feature of our method is the use of an algebraic discretization of the interior product operator and a combinatorial discretization of the wedge product. The governing equations are first rewritten using the exterior calculus notation, replacing vector calculus differential operators by the exterior derivative, Hodge star and wedge product operators. The discretization is then carried out by substituting with the corresponding discrete operators based on the DEC framework. Numerical experiments for flows over surfaces reveal a second order accuracy for the developed scheme when using structured-triangular meshes, and first order accuracy for otherwise unstructured meshes. By construction, the method is conservative in that both mass and vorticity are conserved up to machine precision. The relative error in kinetic energy for inviscid flow test cases converges in a second order fashion with both the mesh size and the time step.
Velocity relaxation of a porous sphere immersed in a viscous incompressible fluid
Felderhof, B. U.
2014-04-01
Velocity relaxation of a spherically symmetric polymer, immersed in a viscous incompressible fluid, and after a sudden small impulse or a sudden twist from a state of rest, is studied on the basis of the linearized Navier-Stokes equations with an added Darcy type drag term. Explicit expressions for the translational and rotational velocity relaxation functions of the polymer and for the flow pattern of the fluid are derived for a uniform permeable sphere. Surprisingly, it is found that the added mass vanishes. For fairly large values of the ratio of sphere radius to the screening length characterizing the permeability, the velocity relaxation functions in the short and intermediate time regime differ significantly from that of a sphere with no-slip boundary condition. At long times, both relaxation functions show universal power law behavior.
Li, Lingxiao; Zheng, Weiying
2017-12-01
In this paper, we propose a Newton-Krylov solver and a Picard-Krylov solver for finite element discrete problem of stationary incompressible magnetohydrodynamic equations in three dimensions. Using a mixed finite element method, we discretize the velocity and the pressure by H1 (Ω)-conforming finite elements and discretize the magnetic field by H (curl , Ω)-conforming edge elements. An efficient preconditioner is proposed to accelerate the convergence of GMRES method for solving linearized discrete problems. By extensive numerical experiments, we demonstrate the robustness of the Newton-Krylov solver for relatively large physical parameters and the optimality with respect to the number of degrees of freedom. Moreover, the numerical experiments show that the Newton-Krylov solver is more robust than the Picard-Krylov solver for large Reynolds number.
Analytical solution for viscous incompressible Stokes flow in a spherical shell
Thieulot, Cedric
2017-11-01
I present a new family of analytical flow solutions to the incompressible Stokes equation in a spherical shell. The velocity is tangential to both inner and outer boundaries, the viscosity is radial and of the power-law type, and the solution has been designed so that the expressions for velocity, pressure, and body force are simple polynomials and therefore simple to implement in (geodynamics) codes. Various flow average values, e.g., the root mean square velocity, are analytically computed. This forms the basis of a numerical benchmark for convection codes and I have implemented it in two finite-element codes: ASPECT and ELEFANT. I report error convergence rates for velocity and pressure.
Chagelishvili, George; Hau, Jan-Niklas; Khujadze, George; Oberlack, Martin
2016-08-01
The linear dynamics of perturbations in smooth shear flows covers the transient exchange of energies between (1) the perturbations and the basic flow and (2) different perturbations modes. Canonically, the linear exchange of energies between the perturbations and the basic flow can be described in terms of the Orr and the lift-up mechanisms, correspondingly for two-dimensional (2D) and three-dimensional (3D) perturbations. In this paper the mechanical basis of the linear transient dynamics is introduced and analyzed for incompressible plane constant shear flows, where we consider the dynamics of virtual fluid particles in the framework of plane perturbations (i.e., perturbations with plane surfaces of constant phase) for the 2D and 3D case. It is shown that (1) the formation of a pressure perturbation field is the result of countermoving neighboring sets of incompressible fluid particles in the flow, (2) the keystone of the energy exchange mechanism between the basic flow and perturbations is the collision of fluid particles with the planes of constant pressure in accordance with the classical theory of elastic collision of particles with a rigid wall, making the pressure field the key player in this process, (3) the interplay of the collision process and the shear flow kinematics describes the transient growth of plane perturbations and captures the physics of the growth, and (4) the proposed mechanical picture allows us to reconstruct the linearized Euler equations in spectral space with a time-dependent shearwise wave number, the linearized Euler equations for Kelvin modes. This confirms the rigor of the presented analysis, which, moreover, yields a natural generalization of the proposed mechanical picture of the transient growth to the well-established linear phenomenon of vortex-wave-mode coupling.
Relation between current sheets and vortex sheets in stationary incompressible MHD
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D. H. Nickeler
2012-03-01
Full Text Available Magnetohydrodynamic configurations with strong localized current concentrations and vortices play an important role in the dissipation of energy in space and astrophysical plasma. Within this work we investigate the relation between current sheets and vortex sheets in incompressible, stationary equilibria. For this approach it is helpful that the similar mathematical structure of magnetohydrostatics and stationary incompressible hydrodynamics allows us to transform static equilibria into stationary ones. The main control function for such a transformation is the profile of the Alfvén-Mach number MA, which is always constant along magnetic field lines, but can change from one field line to another. In the case of a global constant MA, vortices and electric current concentrations are parallel. More interesting is the nonlinear case, where MA varies perpendicular to the field lines. This is a typical situation at boundary layers like the magnetopause, heliopause, the solar wind flowing around helmet streamers and at the boundary of solar coronal holes. The corresponding current and vortex sheets show in some cases also an alignment, but not in every case. For special density distributions in 2-D, it is possible to have current but no vortex sheets. In 2-D, vortex sheets of field aligned-flows can also exist without strong current sheets, taking the limit of small Alfvén Mach numbers into account. The current sheet can vanish if the Alfvén Mach number is (almost constant and the density gradient is large across some boundary layer. It should be emphasized that the used theory is not only valid for small Alfvén Mach numbers MA MA ≲ 1. Connection to other theoretical approaches and observations and physical effects in space plasmas are presented. Differences in the various aspects of theoretical investigations of current sheets and vortex sheets are given.
High order methods for incompressible fluid flow: Application to moving boundary problems
Energy Technology Data Exchange (ETDEWEB)
Bjoentegaard, Tormod
2008-04-15
Fluid flows with moving boundaries are encountered in a large number of real life situations, with two such types being fluid-structure interaction and free-surface flows. Fluid-structure phenomena are for instance apparent in many hydrodynamic applications; wave effects on offshore structures, sloshing and fluid induced vibrations, and aeroelasticity; flutter and dynamic response. Free-surface flows can be considered as a special case of a fluid-fluid interaction where one of the fluids are practically inviscid, such as air. This type of flows arise in many disciplines such as marine hydrodynamics, chemical engineering, material processing, and geophysics. The driving forces for free-surface flows may be of large scale such as gravity or inertial forces, or forces due to surface tension which operate on a much smaller scale. Free-surface flows with surface tension as a driving mechanism include the flow of bubbles and droplets, and the evolution of capillary waves. In this work we consider incompressible fluid flow, which are governed by the incompressible Navier-Stokes equations. There are several challenges when simulating moving boundary problems numerically, and these include - Spatial discretization - Temporal discretization - Imposition of boundary conditions - Solution strategy for the linear equations. These are some of the issues which will be addressed in this introduction. We will first formulate the problem in the arbitrary Lagrangian-Eulerian framework, and introduce the weak formulation of the problem. Next, we discuss the spatial and temporal discretization before we move to the imposition of surface tension boundary conditions. In the final section we discuss the solution of the resulting linear system of equations. (Author). refs., figs., tabs
Ferrer, Esteban
2017-11-01
We present an implicit Large Eddy Simulation (iLES) h / p high order (≥2) unstructured Discontinuous Galerkin-Fourier solver with sliding meshes. The solver extends the laminar version of Ferrer and Willden, 2012 [34], to enable the simulation of turbulent flows at moderately high Reynolds numbers in the incompressible regime. This solver allows accurate flow solutions of the laminar and turbulent 3D incompressible Navier-Stokes equations on moving and static regions coupled through a high order sliding interface. The spatial discretisation is provided by the Symmetric Interior Penalty Discontinuous Galerkin (IP-DG) method in the x-y plane coupled with a purely spectral method that uses Fourier series and allows efficient computation of spanwise periodic three-dimensional flows. Since high order methods (e.g. discontinuous Galerkin and Fourier) are unable to provide enough numerical dissipation to enable under-resolved high Reynolds computations (i.e. as necessary in the iLES approach), we adapt the laminar version of the solver to increase (controllably) the dissipation and enhance the stability in under-resolved simulations. The novel stabilisation relies on increasing the penalty parameter included in the DG interior penalty (IP) formulation. The latter penalty term is included when discretising the linear viscous terms in the incompressible Navier-Stokes equations. These viscous penalty fluxes substitute the stabilising effect of non-linear fluxes, which has been the main trend in implicit LES discontinuous Galerkin approaches. The IP-DG penalty term provides energy dissipation, which is controlled by the numerical jumps at element interfaces (e.g. large in under-resolved regions) such as to stabilise under-resolved high Reynolds number flows. This dissipative term has minimal impact in well resolved regions and its implicit treatment does not restrict the use of large time steps, thus providing an efficient stabilization mechanism for iLES. The IP
Destrade, M.
2010-12-08
We study the propagation of two-dimensional finite-amplitude shear waves in a nonlinear pre-strained incompressible solid, and derive several asymptotic amplitude equations in a simple, consistent and rigorous manner. The scalar Zabolotskaya (Z) equation is shown to be the asymptotic limit of the equations of motion for all elastic generalized neo-Hookean solids (with strain energy depending only on the first principal invariant of Cauchy-Green strain). However, we show that the Z equation cannot be a scalar equation for the propagation of two-dimensional shear waves in general elastic materials (with strain energy depending on the first and second principal invariants of strain). Then, we introduce dispersive and dissipative terms to deduce the scalar Kadomtsev-Petviashvili (KP), Zabolotskaya-Khokhlov (ZK) and Khokhlov- Zabolotskaya-Kuznetsov (KZK) equations of incompressible solid mechanics. © 2010 The Royal Society.
He, Tao; Zhang, Hexin; Zhang, Kai
2018-01-01
In this paper the cell-based smoothed finite element method (CS-FEM) is introduced into two mainstream aspects of computational fluid dynamics: incompressible flows and fluid-structure interaction (FSI). The emphasis is placed on the fluid gradient smoothing which simply requires equal numbers of Gaussian points and smoothing cells in each four-node quadrilateral element. The second-order, smoothed characteristic-based split scheme in conjunction with a pressure stabilization is then presented to settle the incompressible Navier-Stokes equations. As for FSI, CS-FEM is applied to the geometrically nonlinear solid as usual. Following an efficient mesh deformation strategy, block-Gauss-Seidel procedure is adopted to couple all individual fields under the arbitrary Lagriangian-Eulerian description. The proposed solvers are carefully validated against the previously published data for several benchmarks, revealing visible improvements in computed results.
Duddu, Ravindra
2011-10-05
We present a numerical formulation aimed at modeling the nonlinear response of elastic materials using large deformation continuum mechanics in three dimensions. This finite element formulation is based on the Eulerian description of motion and the transport of the deformation gradient. When modeling a nearly incompressible solid, the transport of the deformation gradient is decomposed into its isochoric part and the Jacobian determinant as independent fields. A homogeneous isotropic hyperelastic solid is assumed and B-splines-based finite elements are used for the spatial discretization. A variational multiscale residual-based approach is employed to stabilize the transport equations. The performance of the scheme is explored for both compressible and nearly incompressible applications. The numerical results are in good agreement with theory illustrating the viability of the computational scheme. © 2011 John Wiley & Sons, Ltd.
Lejeunes, S.; Eyheramendy, D.; Boukamel, A.; Delattre, A.; Méo, S.; Ahose, K. D.
2018-02-01
In this paper we investigate the modeling of chemo-physical evolution due to thermo-mechanical loadings at finite strain in soft materials. In particular we discuss the question of a proper and consistent thermodynamical formulation in the case of nearly incompressible materials. The objective of this phenomenological modeling is to represent the thermo-chemo-mechanical aging that occurs in filled rubbers during high-cycle fatigue for some specific loading conditions.
Kou, Jisheng
2013-06-20
We analyze a combined method consisting of the mixed finite element method for pressure equation and the discontinuous Galerkin method for saturation equation for the coupled system of incompressible two-phase flow in porous media. The existence and uniqueness of numerical solutions are established under proper conditions by using a constructive approach. Optimal error estimates in L2(H1) for saturation and in L∞(H(div)) for velocity are derived. Copyright © 2013 John Wiley & Sons, Ltd.
B R Sharma*, Nabajyoti Dutta
2016-01-01
In the present study, the effects of chemical reaction and thermal radiation on unsteady MHD flow of a viscous, electrically conducting and incompressible fluid mixture past a moving vertical cylinder is studied. The fluid is a gray, absorbing-emitting but non scattering medium and the Rosseland approximation is used to describe the radiative heat flux in the energy equation. The governing dimensionless coupled non-linear partial differential equations are solved numerically using finite di...
Liang, H; Shi, B C; Guo, Z L; Chai, Z H
2014-05-01
In this paper, a phase-field-based multiple-relaxation-time lattice Boltzmann (LB) model is proposed for incompressible multiphase flow systems. In this model, one distribution function is used to solve the Chan-Hilliard equation and the other is adopted to solve the Navier-Stokes equations. Unlike previous phase-field-based LB models, a proper source term is incorporated in the interfacial evolution equation such that the Chan-Hilliard equation can be derived exactly and also a pressure distribution is designed to recover the correct hydrodynamic equations. Furthermore, the pressure and velocity fields can be calculated explicitly. A series of numerical tests, including Zalesak's disk rotation, a single vortex, a deformation field, and a static droplet, have been performed to test the accuracy and stability of the present model. The results show that, compared with the previous models, the present model is more stable and achieves an overall improvement in the accuracy of the capturing interface. In addition, compared to the single-relaxation-time LB model, the present model can effectively reduce the spurious velocity and fluctuation of the kinetic energy. Finally, as an application, the Rayleigh-Taylor instability at high Reynolds numbers is investigated.
Porée, Jonathan; Garcia, Damien; Chayer, Boris; Ohayon, Jacques; Cloutier, Guy
2015-12-01
Plane strain tensor estimation using non-invasive vascular ultrasound elastography (NIVE) can be difficult to achieve using conventional focus beamforming due to limited lateral resolution and frame rate. Recent developments in compound plane wave (CPW) imaging have led to high speed and high resolution imaging. In this study, we present the performance of NIVE using coherent CPW. We show the impact of CPW beamforming on strain estimates compared to conventional focus sequences. To overcome the inherent variability of lateral strains, associated with the low lateral resolution of linear array transducers, we use the plane strain incompressibility to constrain the estimator. Taking advantage of the approximate tenfold increase in frame rate of CPW compared with conventional focus imaging, we introduce a time-ensemble estimation approach to further improve the elastogram quality. By combining CPW imaging with the constrained Lagrangian speckle model estimator, we observe an increase in elastography quality (∼ 10 dB both in signal-to-noise and contrast-to-noise ratios) over a wide range of applied strains (0.02 to 3.2%).
A simple and efficient outflow boundary condition for the incompressible Navier–Stokes equations
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Yibao Li
2017-01-01
Full Text Available Many researchers have proposed special treatments for outlet boundary conditions owing to lack of information at the outlet. Among them, the simplest method requires a large enough computational domain to prevent or reduce numerical errors at the boundaries. However, an efficient method generally requires special treatment to overcome the problems raised by the outlet boundary condition used. For example, mass flux is not conserved and the fluid field is not divergence-free at the outlet boundary. Overcoming these problems requires additional computational cost. In this paper, we present a simple and efficient outflow boundary condition for the incompressible Navier–Stokes equations, aiming to reduce the computational domain for simulating flow inside a long channel in the streamwise direction. The proposed outflow boundary condition is based on the transparent equation, where a weak formulation is used. The pressure boundary condition is derived by using the Navier–Stokes equations and the outlet flow boundary condition. In the numerical algorithm, a staggered marker-and-cell grid is used and temporal discretization is based on a projection method. The intermediate velocity boundary condition is consistently adopted to handle the velocity–pressure coupling. Characteristic numerical experiments are presented to demonstrate the robustness and accuracy of the proposed numerical scheme. Furthermore, the agreement of computational results from small and large domains suggests that our proposed outflow boundary condition can significantly reduce computational domain sizes.
Tearing Instability of a Current Sheet Forming by Sheared Incompressible Flow
Tolman, Elizabeth; Loureiro, Nuno; Uzdensky, Dmitri
2017-10-01
Sweet-Parker current sheets are unstable to the tearing mode, suggesting they will not form in physical systems. Understanding magnetic reconnection thus requires study of the stability of a current sheet as it forms. Such formation can occur as a result of sheared, sub-Alfvénic incompressible flows into and along the sheet. This work presents an analysis of how tearing perturbations behave in a current sheet forming under the influence of such flows, beginning with a phase when the growth rate of the tearing mode is small and the behavior of perturbations is primarily governed by ideal MHD. Later, after the tearing growth rate becomes significant relative to the time scale of the driving flows, the flows cause a slight reduction in the tearing growth rate and wave vector of the dominant mode. Once the tearing mode enters the nonlinear regime, the flows accelerate the tearing growth slightly; during X-point collapse, the flows have negligible effect on the system behavior. This analysis allows greater understanding of reconnection in evolving systems and increases confidence in the application of tools developed in time-independent current sheets to changing current sheets. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship.
Kim, J. S.; Chang, K. S.
1984-06-01
Transient as well as oscillating two-dimensional boundary layers are solved numerically by using a noniterative implicit finite difference scheme which is second-order accurate both in time and space. To obtain the exact spatial initial condition, the solution is obtained of parabolic partial differential equations at the initial plane which are reduced from the full biparabolic equations valid in the main time-space domain. Formulations are made first for incompressible flow, and then for compressible boundary layers so that the effect of temperature-induced compressibility can be considered. The method is applied to the unsteady laminar boundary layers with large temporal flow disturbances. Examples are transition to Falkner-Skan flow, oscillatory Blasius flow, constantly accelerated stagnation point flow and harmonically fluctuating flow past a circular cylinder, with or without the compressibility effect taken into account for the last two cases. Comparison with the existing data has demonstrated the excellency of the present method both in accuracy and computer-time economy.
Unsteady incompressible MHD boundary layer on porous aerofoil in high accelerating fluid flow
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Ivanović Dečan J.
2002-01-01
Full Text Available The fluid, flowing past the surface, is incompressible and its electro-conductivity is constant. The present magnetic field is homogenous and perpendicular to the surface and through the porous contour the fluid has been injected or ejected. In order to study this problem, a polyparametric method known as generalized similarity method has been established. The corresponding equations of unsteady boundary layer, by introducing the appropriate variable transformations, momentum and energy equations and three similarity parameters sets, being transformed into generalized form. The numerical integration of the generalized equation with boundary conditions has been performed by means of the difference schemes and by using Tridiagonal Algorithm Method with iterations in the four parametric and twice localized approximation. So obtained generalized solutions are used to calculate the shear stress distribution in laminar-turbulent transition of unsteady boundary layer on porous high accelerating aerofoil. It's shown that for both in confuser and in diffuser regions the ejection of fluid postpones the boundary layer separation, and vice versa the fluid injection favors the separation. For both injection and ejection of fluid, the magnetic field increases the friction and postpones the laminar-turbulent transition.
A meshless scheme for incompressible fluid flow using a velocity-pressure correction method
Bourantas, Georgios
2013-12-01
A meshless point collocation method is proposed for the numerical solution of the steady state, incompressible Navier-Stokes (NS) equations in their primitive u-v-p formulation. The flow equations are solved in their strong form using either a collocated or a semi-staggered "grid" configuration. The developed numerical scheme approximates the unknown field functions using the Moving Least Squares approximation. A velocity, along with a pressure correction scheme is applied in the context of the meshless point collocation method. The proposed meshless point collocation (MPC) scheme has the following characteristics: (i) it is a truly meshless method, (ii) there is no need for pressure boundary conditions since no pressure constitutive equation is solved, (iii) it incorporates simplicity and accuracy, (iv) results can be obtained using collocated or semi-staggered "grids", (v) there is no need for the usage of a curvilinear system of coordinates and (vi) it can solve steady and unsteady flows. The lid-driven cavity flow problem, for Reynolds numbers up to 5000, has been considered, by using both staggered and collocated grid configurations. Following, the Backward-Facing Step (BFS) flow problem was considered for Reynolds numbers up to 800 using a staggered grid. As a final example, the case of a laminar flow in a two-dimensional tube with an obstacle was examined. © 2013 Elsevier Ltd.
Kashefi, Ali; Staples, Anne
2016-11-01
Coarse grid projection (CGP) methodology is a novel multigrid method for systems involving decoupled nonlinear evolution equations and linear elliptic equations. The nonlinear equations are solved on a fine grid and the linear equations are solved on a corresponding coarsened grid. Mapping functions transfer data between the two grids. Here we propose a version of CGP for incompressible flow computations using incremental pressure correction methods, called IFEi-CGP (implicit-time-integration, finite-element, incremental coarse grid projection). Incremental pressure correction schemes solve Poisson's equation for an intermediate variable and not the pressure itself. This fact contributes to IFEi-CGP's efficiency in two ways. First, IFEi-CGP preserves the velocity field accuracy even for a high level of pressure field grid coarsening and thus significant speedup is achieved. Second, because incremental schemes reduce the errors that arise from boundaries with artificial homogenous Neumann conditions, CGP generates undamped flows for simulations with velocity Dirichlet boundary conditions. Comparisons of the data accuracy and CPU times for the incremental-CGP versus non-incremental-CGP computations are presented.
Silvis, Maurits H; Verstappen, Roel
2016-01-01
We study the construction of subgrid-scale models for large-eddy simulation of incompressible turbulent flows. In particular, we aim to consolidate a systematic approach of constructing subgrid-scale models, based on the idea that it is desirable that subgrid-scale models are consistent with the properties of the Navier-Stokes equations and the turbulent stresses. To that end, we first discuss in detail the symmetries of the Navier-Stokes equations, and the near-wall scaling behavior, realizability and dissipation properties of the turbulent stresses. We furthermore summarize the requirements that subgrid-scale models have to satisfy in order to preserve these important mathematical and physical properties. In this fashion, a framework of model constraints arises that we apply to analyze the behavior of a number of existing subgrid-scale models that are based on the local velocity gradient. We show that these subgrid-scale models do not satisfy all the desired properties, after which we explain that this is p...
An incompressible two-dimensional multiphase particle-in-cell model for dense particle flows
Energy Technology Data Exchange (ETDEWEB)
Snider, D.M. [SAIC, Albuquerque, NM (United States); O`Rourke, P.J. [Los Alamos National Lab., NM (United States); Andrews, M.J. [Texas A and M Univ., College Station, TX (United States). Dept. of Mechanical Engineering
1997-06-01
A two-dimensional, incompressible, multiphase particle-in-cell (MP-PIC) method is presented for dense particle flows. The numerical technique solves the governing equations of the fluid phase using a continuum model and those of the particle phase using a Lagrangian model. Difficulties associated with calculating interparticle interactions for dense particle flows with volume fractions above 5% have been eliminated by mapping particle properties to a Eulerian grid and then mapping back computed stress tensors to particle positions. This approach utilizes the best of Eulerian/Eulerian continuum models and Eulerian/Lagrangian discrete models. The solution scheme allows for distributions of types, sizes, and density of particles, with no numerical diffusion from the Lagrangian particle calculations. The computational method is implicit with respect to pressure, velocity, and volume fraction in the continuum solution thus avoiding courant limits on computational time advancement. MP-PIC simulations are compared with one-dimensional problems that have analytical solutions and with two-dimensional problems for which there are experimental data.
Samtaney, Ravi; Mohamed, Mamdouh; Hirani, Anil
2015-11-01
We present examples of numerical solutions of incompressible flow on 2D curved domains. The Navier-Stokes equations are first rewritten using the exterior calculus notation, replacing vector calculus differential operators by the exterior derivative, Hodge star and wedge product operators. A conservative discretization of Navier-Stokes equations on simplicial meshes is developed based on discrete exterior calculus (DEC). The discretization is then carried out by substituting the corresponding discrete operators based on the DEC framework. By construction, the method is conservative in that both the discrete divergence and circulation are conserved up to machine precision. The relative error in kinetic energy for inviscid flow test cases converges in a second order fashion with both the mesh size and the time step. Numerical examples include Taylor vortices on a sphere, Stuart vortices on a sphere, and flow past a cylinder on domains with varying curvature. Supported by the KAUST Office of Competitive Research Funds under Award No. URF/1/1401-01.
Simulation of incompressible two-phase flow in porous media with large timesteps
Cogswell, Daniel A.; Szulczewski, Michael L.
2017-09-01
Multiphase flow in porous media occurs in several disciplines including petroleum reservoir engineering, petroleum systems' analysis, and CO2 sequestration. While simulations often use a fully implicit discretization to increase the time step size, restrictions on the time step often exist due to non-convergence of the nonlinear solver (e.g. Newton's method). Here this problem is addressed for the Buckley-Leverett equations, which model incompressible, immiscible, two-phase flow with no capillary potential. The equations are recast as a gradient flow using the phase-field method, and a convex energy splitting scheme is applied to enable large timesteps, even for high degrees of heterogeneity in permeability and viscosity. By using the phase-field formulation as a homotopy map, the underlying hyperbolic flow equations can be solved with large timesteps. For a heterogeneous test problem, the new homotopy method allows the timestep to be increased by more than six orders of magnitude relative to the unmodified equations while maintaining convergence.
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Abdelraheem M. Aly
2015-02-01
Full Text Available A stabilized incompressible smoothed particle hydrodynamics (ISPH method with the addition of a density invariant relaxation condition in the pressure calculations is applied to simulations of highly nonlinear liquid sloshing problems. By applying the Neumann boundary condition when solving pressure, the performance of the present ISPH method is enhanced significantly. Two large-amplitude free sloshing problems under a resonance sway excitation were carried out in a square and a rectangular tank with filling-depths ratios of 20% and 50% of tank height, respectively, and compared with the available published experimental results. To extend the validation of the method, numerical simulations for sloshing problems with the varying density of a floating body as well as a middle baffle, which also generates strongly nonlinear free surface flow, were conducted. The results showed that the present ISPH method produces smooth pressure distribution and significantly reduces spurious oscillation. The proposed ISPH method was shown to be robust and accurate in long time simulation of highly nonlinear sloshing problems.
Arbañil, José D V; Zanchin, Vilson T
2014-01-01
We investigate the properties of relativistic star spheres made of an electrically charged incompressible fluid, generalizing, thus, the Schwarzschild interior solution. The investigation is carried by integrating numerically the hydrostatic equilibrium equation, i.e., the Tolman-Oppenheimer-Volkoff (TOV) equation, with the hypothesis that the charge distribution is proportional to the energy density. We match the interior to a Reissner-Nordstr\\"om exterior, and study some features of these star spheres such as the total mass $M$, the radius $R$, and the total charge $Q$. We also display the pressure profile. For star spheres made of a perfect fluid there is the Buchdahl bound, $R/M\\geq 9/4$, a compactness bound found from generic principles. For the Schwarzschild interior solution there is also the known compactness limit, the interior Schwarzschild limit where the configurations attain infinite central pressure, given by $R/M=9/4$, yielding an instance where the Buchdahl bound is saturated. We study this li...
An incompressible fluid flow model with mutual information for MR image registration
Tsai, Leo; Chang, Herng-Hua
2013-03-01
Image registration is one of the fundamental and essential tasks within image processing. It is a process of determining the correspondence between structures in two images, which are called the template image and the reference image, respectively. The challenge of registration is to find an optimal geometric transformation between corresponding image data. This paper develops a new MR image registration algorithm that uses a closed incompressible viscous fluid model associated with mutual information. In our approach, we treat the image pixels as the fluid elements of a viscous fluid flow governed by the nonlinear Navier-Stokes partial differential equation (PDE). We replace the pressure term with the body force mainly used to guide the transformation with a weighting coefficient, which is expressed by the mutual information between the template and reference images. To solve this modified Navier-Stokes PDE, we adopted the fast numerical techniques proposed by Seibold1. The registration process of updating the body force, the velocity and deformation fields is repeated until the mutual information weight reaches a prescribed threshold. We applied our approach to the BrainWeb and real MR images. As consistent with the theory of the proposed fluid model, we found that our method accurately transformed the template images into the reference images based on the intensity flow. Experimental results indicate that our method is of potential in a wide variety of medical image registration applications.
Argani, L P; Bigoni, D; Capuani, D; Movchan, N V
2014-09-08
The infinite-body three-dimensional Green's function set (for incremental displacement and mean stress) is derived for the incremental deformation of a uniformly strained incompressible, nonlinear elastic body. Particular cases of the developed formulation are the Mooney-Rivlin elasticity and the J2-deformation theory of plasticity. These Green's functions are used to develop a boundary integral equation framework, by introducing an ad hoc potential, which paves the way for a boundary element formulation of three-dimensional problems of incremental elasticity. Results are used to investigate the behaviour of a material deformed near the limit of ellipticity and to reveal patterns of shear failure. In fact, within the investigated three-dimensional framework, localized deformations emanating from a perturbation are shown to be organized in conical geometries rather than in planar bands, so that failure is predicted to develop through curved and thin surfaces of intense shearing, as can for instance be observed in the cup-cone rupture of ductile metal bars.
Detached Eddy Simulations (des) of Incompressible Turbulent Flows Using the Finite Element Method
Laskowski, Gregory M.; McCallen, Rose C.; Dunn, Timothy A.; Salari, Kambiz
2001-11-01
An explicit Galerkin finite-element (GFEM) formulation of the Spalart-Allmaras (SA) 1-equation turbulent transport model was implemented into an incompressible GFEM code, using both a RANS formulation and a DES formulation. DES is a new technique for simulating/modeling turbulence using a hybrid RANS/LES formulation. The turbulent viscosity is constructed from an intermediate viscosity obtained from the transport equation which is spatially discretized using Q1 elements and integrated in time via forward Euler time integration. Simulations of plane channel flow were conducted to validate the implementation: SA-RANS, SA-DES and Smagorinsky. Preliminary results indicate that the modeling and grid resolution are strongly related, as expected, and that good results can be obtained on the appropriate grid. Using a RANS-grid, very good agreement was observed between the SA-RANS results and theory, namely the Log Law of the Wall (LLW), especially in the viscous sub-layer and, to a lesser extent, in the log- layer. It was observed that near the wall, the SA-DES model behaved as a RANS model, and away from the wall it was more characteristic of an LES model. (This work was performed under the auspices of the U.S. Department of Energy by Lawerence Livermore National Laboratory under Contract W-7405-ENG-48.)
A Diffuse Interface Model for Incompressible Two-Phase Flow with Large Density Ratios
Xie, Yu
2016-10-04
In this chapter, we explore numerical simulations of incompressible and immiscible two-phase flows. The description of the fluid–fluid interface is introduced via a diffuse interface approach. The two-phase fluid system is represented by a coupled Cahn–Hilliard Navier–Stokes set of equations. We discuss challenges and approaches to solving this coupled set of equations using a stabilized finite element formulation, especially in the case of a large density ratio between the two fluids. Specific features that enabled efficient solution of the equations include: (i) a conservative form of the convective term in the Cahn–Hilliard equation which ensures mass conservation of both fluid components; (ii) a continuous formula to compute the interfacial surface tension which results in lower requirement on the spatial resolution of the interface; and (iii) a four-step fractional scheme to decouple pressure from velocity in the Navier–Stokes equation. These are integrated with standard streamline-upwind Petrov–Galerkin stabilization to avoid spurious oscillations. We perform numerical tests to determine the minimal resolution of spatial discretization. Finally, we illustrate the accuracy of the framework using the analytical results of Prosperetti for a damped oscillating interface between two fluids with a density contrast.
Wang, Zhiheng
2014-12-10
A meshless local radial basis function method is developed for two-dimensional incompressible Navier-Stokes equations. The distributed nodes used to store the variables are obtained by the philosophy of an unstructured mesh, which results in two main advantages of the method. One is that the unstructured nodes generation in the computational domain is quite simple, without much concern about the mesh quality; the other is that the localization of the obtained collocations for the discretization of equations is performed conveniently with the supporting nodes. The algebraic system is solved by a semi-implicit pseudo-time method, in which the convective and source terms are explicitly marched by the Runge-Kutta method, and the diffusive terms are implicitly solved. The proposed method is validated by several benchmark problems, including natural convection in a square cavity, the lid-driven cavity flow, and the natural convection in a square cavity containing a circular cylinder, and very good agreement with the existing results are obtained.
Simulation of incompressible flows with heat and mass transfer using parallel finite element method
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Jalal Abedi
2003-02-01
Full Text Available The stabilized finite element formulations based on the SUPG (Stream-line-Upwind/Petrov-Galerkin and PSPG (Pressure-Stabilization/Petrov-Galerkin methods are developed and applied to solve buoyancy-driven incompressible flows with heat and mass transfer. The SUPG stabilization term allows us to solve flow problems at high speeds (advection dominant flows and the PSPG term eliminates instabilities associated with the use of equal order interpolation functions for both pressure and velocity. The finite element formulations are implemented in parallel using MPI. In parallel computations, the finite element mesh is partitioned into contiguous subdomains using METIS, which are then assigned to individual processors. To ensure a balanced load, the number of elements assigned to each processor is approximately equal. To solve nonlinear systems in large-scale applications, we developed a matrix-free GMRES iterative solver. Here we totally eliminate a need to form any matrices, even at the element levels. To measure the accuracy of the method, we solve 2D and 3D example of natural convection flows at moderate to high Rayleigh numbers.
A Reduced Local Discontinuous Galerkin Method for Nearly Incompressible Linear Elasticity
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Xuehai Huang
2013-01-01
Full Text Available A reduced local discontinuous Galerkin (RLDG method for nearly incompressible linear elasticity is proposed in this paper, which is locking-free. RLDG method can be formally regarded as a special case of LDG method with C11=0. However, RLDG method is actually not covered by LDG method, where C11 must be chosen to be positive to ensure the stability of LDG method. RLDG method can also be considered as the localization of some symmetric nonconforming mixed finite element method. The implementation of RLDG method is discussed. By introducing a lifting operator as LDG method, RLDG method can be rewritten as primal formulation with unknown displacement only. Next, we obtain that the convergence rates of the approximation to stress tensor in energy norm and displacement in L2-norm are O(hk and O(hk+1, respectively, which are both uniform with respect to λ. Moreover, we obtain a H(div-conforming displacement by projecting the displacement and corresponding numerical trace of RLDG method into the Raviart-Thomas element space. And then we analyze the error estimates of this postprocessed displacement in H(div-seminorm and L2-norm, which are also uniform with respect to λ. Finally, some numerical results are shown to demonstrate the theoretical results.
Chen, Z.; Shu, C.; Tan, D.
2017-05-01
In this paper, a three-dimensional simplified and unconditionally stable lattice Boltzmann method (3D-USLBM) is proposed for simulating incompressible isothermal/thermal flows. This method is developed by reconstructing solutions to the macroscopic governing equations recovered from the lattice Boltzmann equation and resolved in a predictor-corrector scheme. The final formulations of 3D-USLBM only involve the equilibrium and the non-equilibrium distribution functions. Among them, the former is calculated from the macroscopic variables and the latter is evaluated from the difference between two equilibrium distribution functions at different locations and time levels. Thus, 3D-USLBM directly tracks the evolution of macroscopic variables, which yields lower cost in virtual memory and facilitates the implementation of physical boundary conditions. A von Neumann stability analysis was performed on the present method to theoretically prove its unconditional stability. By imposing a regular Lagrange interpolation algorithm, this method can be flexibly extended to a non-uniform Cartesian mesh or body-fitted mesh with curved boundaries. Four numerical tests, that is, plane Poiseuille flow, 3D lid-driven cavity flow and 3D natural convection in a cubic cavity, and concentric annulus, were conducted to verify the stability, accuracy, and flexibility of the presented method.
A Stabilized Incompressible SPH Method by Relaxing the Density Invariance Condition
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Mitsuteru Asai
2012-01-01
Full Text Available A stabilized Incompressible Smoothed Particle Hydrodynamics (ISPH is proposed to simulate free surface flow problems. In the ISPH, pressure is evaluated by solving pressure Poisson equation using a semi-implicit algorithm based on the projection method. Even if the pressure is evaluated implicitly, the unrealistic pressure fluctuations cannot be eliminated. In order to overcome this problem, there are several improvements. One is small compressibility approach, and the other is introduction of two kinds of pressure Poisson equation related to velocity divergence-free and density invariance conditions, respectively. In this paper, a stabilized formulation, which was originally proposed in the framework of Moving Particle Semi-implicit (MPS method, is applied to ISPH in order to relax the density invariance condition. This formulation leads to a new pressure Poisson equation with a relaxation coefficient, which can be estimated by a preanalysis calculation. The efficiency of the proposed formulation is tested by a couple of numerical examples of dam-breaking problem, and its effects are discussed by using several resolution models with different particle initial distances. Also, the effect of eddy viscosity is briefly discussed in this paper.
A new class of massively parallel direction splitting for the incompressible Navier–Stokes equations
Guermond, J.L.
2011-06-01
We introduce in this paper a new direction splitting algorithm for solving the incompressible Navier-Stokes equations. The main originality of the method consists of using the operator (I-∂xx)(I-∂yy)(I-∂zz) for approximating the pressure correction instead of the Poisson operator as done in all the contemporary projection methods. The complexity of the proposed algorithm is significantly lower than that of projection methods, and it is shown the have the same stability properties as the Poisson-based pressure-correction techniques, either in standard or rotational form. The first-order (in time) version of the method is proved to have the same convergence properties as the classical first-order projection techniques. Numerical tests reveal that the second-order version of the method has the same convergence rate as its second-order projection counterpart as well. The method is suitable for parallel implementation and preliminary tests show excellent parallel performance on a distributed memory cluster of up to 1024 processors. The method has been validated on the three-dimensional lid-driven cavity flow using grids composed of up to 2×109 points. © 2011 Elsevier B.V.
Dual plane problems for creeping flow of power-law incompressible medium
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Dmitriy S. Petukhov
2016-09-01
Full Text Available In this paper, we consider the class of solutions for a creeping plane flow of incompressible medium with power-law rheology, which are written in the form of the product of arbitrary power of the radial coordinate by arbitrary function of the angular coordinate of the polar coordinate system covering the plane. This class of solutions represents the asymptotics of fields in the vicinity of singular points in the domain occupied by the examined medium. We have ascertained the duality of two problems for a plane with wedge-shaped notch, at which boundaries in one of the problems the vector components of the surface force vanish, while in the other—the vanishing components are the vector components of velocity, We have investigated the asymptotics and eigensolutions of the dual nonlinear eigenvalue problems in relation to the rheological exponent and opening angle of the notch for the branch associated with the eigenvalue of the Hutchinson–Rice–Rosengren problem learned from the problem of stress distribution over a notched plane for a power law medium. In the context of the dual problem we have determined the velocity distribution in the flow of power-law medium at the vertex of a rigid wedge, We have also found another two eigenvalues, one of which was determined by V. V. Sokolovsky for the problem of power-law fluid flow in a convergent channel.
A Note on an Analytic Solution for an Incompressible Fluid-Conveying Pipeline System
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Vincent O. S. Olunloyo
2017-01-01
Full Text Available This paper presents an integral transform analytic solution to the equations governing a fluid-conveying pipeline segment where a gyroscopic or Coriolis force effect is taken into consideration. The mathematical model idealizes a segment of the pipeline as an elastic beam conveying an incompressible fluid. It is clearly shown that when such a system is supported at both ends and in a free motion, the Coriolis force dissipates no energy (or simply does not work as it generates conjugate complex vibratory components for all flow velocities. It is demonstrated that the modal natural frequencies can be computed from the algebraic products of the complex frequency pairs. Clearly, the patterns of the characteristics of the system’s natural frequencies are seen partly when the real and imaginary components are plotted, as widely seen in the literature. Nonetheless, results from this study revealed that a continuity profile exists to connect the subcritical, critical, and postcritical vibratory behaviours when the absolute values are plotted for any velocity. In the meantime, the efficacy and versatility of this method against the usual assumed spatial or temporal modal solutions are demonstrated by confirming the predictions and validity of results of earlier workers such as Paidoussis, Ziegler, and others where pre- and postdivergence behaviours are exhibited.
Aithal, Abhiram; Ferrante, Antonino
2017-11-01
In order to perform direct numerical simulations (DNS) of turbulent flows over curved surfaces and axisymmetric bodies, we have developed the numerical methodology to solve the incompressible Navier-Stokes (NS) equations in curvilinear coordinates for orthogonal meshes. The orthogonal meshes are generated by solving a coupled system of non-linear Poisson equations. The NS equations in orthogonal curvilinear coordinates are discretized in space on a staggered mesh using second-order central-difference scheme and are solved with an FFT-based pressure-correction method. The momentum equation is integrated in time using the second-order Adams-Bashforth scheme. The velocity field is advanced in time by applying the pressure correction to the approximate velocity such that it satisfies the divergence free condition. The novelty of the method stands in solving the variable coefficient Poisson equation for pressure using an FFT-based Poisson solver rather than the slower multigrid methods. We present the verification and validation results of the new numerical method and the DNS results of transitional flow over a curved axisymmetric body.
Quasi-periodic non-stationary solutions of 3D Euler equations for incompressible flow
Ershkov, Sergey V
2015-01-01
A novel derivation of non-stationary solutions of 3D Euler equations for incompressible inviscid flow is considered here. Such a solution is the product of 2 separated parts: - one consisting of the spatial component and the other being related to the time dependent part. Spatial part of a solution could be determined if we substitute such a solution to the equations of motion (equation of momentum) with the requirement of scale-similarity in regard to the proper component of spatial velocity. So, the time-dependent part of equations of momentum should depend on the time-parameter only. The main result, which should be outlined, is that the governing (time-dependent) ODE-system consist of 2 Riccati-type equations in regard to each other, which has no solution in general case. But we obtain conditions when each component of time-dependent part is proved to be determined by the proper elliptical integral in regard to the time-parameter t, which is a generalization of the class of inverse periodic functions.
A Mass Conservation Scheme for Level Set Method Applied to Multiphase Incompressible Flows
Salih, A.; Ghosh Moulic, S.
2013-06-01
Despite the inherent advantages of the level set method in the computation of multiphase flows, the principal drawback has been the lack of conservation of mass (or volume in incompressible flows). While the level set community has resorted to the use of highly accurate schemes like a fifth-order Weighted Essentially Non-Oscillatory (WENO) scheme for the solution of level set equations, it is seen that for certain classes of problems the volume loss is still high. In order to circumvent this limitation of the level set method, in this paper we propose a volume-reinitialization scheme, wherein volume correction is accomplished by solving an appropriate equation for level set function after every time step. The volume-reinitialization scheme recognizes the local curvature of the interface while correcting the volume loss. The efficacy of the proposed technique has been tested for several problems that include determination of equilibrium shape of free surface in a rotating cylindrical container and simulation of zero-gravity drop oscillations. It is seen that there is a dramatic increase in the performance of the level set method when used in conjunction with volume-reinitialization and this strategy seems to hold promise for a wide class of problems.
Visual art and visual perception
Koenderink, Jan J.
2015-01-01
Visual art and visual perception ‘Visual art’ has become a minor cul-de-sac orthogonal to THE ART of the museum directors and billionaire collectors. THE ART is conceptual, instead of visual. Among its cherished items are the tins of artist’s shit (Piero Manzoni, 1961, Merda d’Artista) “worth their
Merzkirch, Wolfgang
1974-01-01
Flow Visualization describes the most widely used methods for visualizing flows. Flow visualization evaluates certain properties of a flow field directly accessible to visual perception. Organized into five chapters, this book first presents the methods that create a visible flow pattern that could be investigated by visual inspection, such as simple dye and density-sensitive visualization methods. It then deals with the application of electron beams and streaming birefringence. Optical methods for compressible flows, hydraulic analogy, and high-speed photography are discussed in other cha
Kraak, M.J.; Wright, James D.
2015-01-01
The cartographic visualization process, based on the statement “How do I say what to whom, and is it effective?” is explained for both presenting and exploring spatiotemporal data. The visualization environment and required functionality are described
A fixed-mesh method for incompressible flow structure systems with finite solid deformations
Zhao, Hong; Freund, Jonathan B.; Moser, Robert D.
2008-03-01
A fixed-mesh algorithm is proposed for simulating flow-structure interactions such as those occurring in biological systems, in which both the fluid and solid are incompressible and the solid deformations are large. Several of the well-known difficulties in simulating such flow-structure interactions are avoided by formulating a single set of equations of motion on a fixed Eulerian mesh. The solid's deformation is tracked to compute elastic stresses by an overlapping Lagrangian mesh. In this way, the flow-structure interaction is formulated as a distributed body force and singular surface force acting on an otherwise purely fluid system. These forces, which depend on the solid elastic stress distribution, are computed on the Lagrangian mesh by a standard finite-element method and then transferred to the fixed Eulerian mesh, where the joint momentum and continuity equations are solved by a finite-difference method. The constitutive model for the solid can be quite general. For the force transfer, standard immersed-boundary and immersed-interface methods can be used and are demonstrated. We have also developed and demonstrated a new projection method that unifies the transfer of the surface and body forces in a way that exactly conserves momentum; the interface is still effectively sharp for this approach. The spatial convergence of the method is observed to be between first- and second-order, as in most immersed-boundary methods for membrane flows. The algorithm is demonstrated by the simulations of an advected elastic disk, a flexible leaflet in an oscillating flow, and a model of a swimming jellyfish.
Advances in Spectral Methods for UQ in Incompressible Navier-Stokes Equations
Le Maitre, Olivier
2014-01-06
In this talk, I will present two recent contributions to the development of efficient methodologies for uncertainty propagation in the incompressible Navier-Stokes equations. The first one concerns the reduced basis approximation of stochastic steady solutions, using Proper Generalized Decompositions (PGD). An Arnoldi problem is projected to obtain a low dimensional Galerkin problem. The construction then amounts to the resolution of a sequence of uncoupled deterministic Navier-Stokes like problem and simple quadratic stochastic problems, followed by the resolution of a low-dimensional coupled quadratic stochastic problem, with a resulting complexity which has to be contrasted with the dimension of the whole Galerkin problem for classical spectral approaches. An efficient algorithm for the approximation of the stochastic pressure field is also proposed. Computations are presented for uncertain viscosity and forcing term to demonstrate the effectiveness of the reduced method. The second contribution concerns the computation of stochastic periodic solutions to the Navier-Stokes equations. The objective is to circumvent the well-known limitation of spectral methods for long-time integration. We propose to directly determine the stochastic limit-cycles through the definition of its stochastic period and an initial condition over the cycle. A modified Newton method is constructed to compute iteratively both the period and initial conditions. Owing to the periodic character of the solution, and by introducing an appropriate time-scaling, the solution can be approximated using low-degree polynomial expansions with large computational saving as a result. The methodology is illustrated for the von-Karman flow around a cylinder with stochastic inflow conditions.
A staggered overset grid method for resolved simulation of incompressible flow around moving spheres
Vreman, A. W.
2017-03-01
An overset grid method for resolved simulation of incompressible (turbulent) flows around moving spherical particles is presented. The Navier-Stokes equations in spherical coordinates are solved on body-fitted spherical polar grids attached to the moving spheres. These grids are overset on a fixed Cartesian background grid, where the Navier-Stokes equations in Cartesian coordinates are solved. The standard second-order staggered finite difference scheme is used on each grid. The velocities and pressures on different grids are coupled by third-order Lagrange interpolations. The method, implemented in the form of a Message Passing Interface parallel program, has been validated for a range of flows around spheres. In a first validation section, the results of simulations of four Stokes flows around a single moving sphere are compared with classical analytical results. The first three cases are the flows due to a translating, an oscillating sphere and a rotating sphere. The numerically produced velocity and pressure fields appear to converge to the corresponding (transient) analytical solutions in the maximum norm. The fourth Stokes case is the flow due to an instantaneously accelerated sphere. For this case, the results are compared with the corresponding numerical solution of the Basset-Boussinesq-Oseen equation. In a second validation section, results of three Navier-Stokes flows around one or more moving spheres are presented. These test configurations are a moving face-centered cubic array of spheres, laminar channel flow with a falling a sphere, and freely moving small spheres in a Taylor-Green flow. Results for the flow with the falling sphere are compared with the results from the literature on immersed boundary methods.
Banks, J. W.; Henshaw, W. D.; Schwendeman, D. W.; Tang, Qi
2017-08-01
A stable partitioned algorithm is developed for fluid-structure interaction (FSI) problems involving viscous incompressible flow and rigid bodies. This added-mass partitioned (AMP) algorithm remains stable, without sub-iterations, for light and even zero mass rigid bodies when added-mass and viscous added-damping effects are large. The scheme is based on a generalized Robin interface condition for the fluid pressure that includes terms involving the linear acceleration and angular acceleration of the rigid body. Added-mass effects are handled in the Robin condition by inclusion of a boundary integral term that depends on the pressure. Added-damping effects due to the viscous shear forces on the body are treated by inclusion of added-damping tensors that are derived through a linearization of the integrals defining the force and torque. Added-damping effects may be important at low Reynolds number, or, for example, in the case of a rotating cylinder or rotating sphere when the rotational moments of inertia are small. In this first part of a two-part series, the properties of the AMP scheme are motivated and evaluated through the development and analysis of some model problems. The analysis shows when and why the traditional partitioned scheme becomes unstable due to either added-mass or added-damping effects. The analysis also identifies the proper form of the added-damping which depends on the discrete time-step and the grid-spacing normal to the rigid body. The results of the analysis are confirmed with numerical simulations that also demonstrate a second-order accurate implementation of the AMP scheme.
Numerical Solution of Incompressible Navier-Stokes Equations Using a Fractional-Step Approach
Kiris, Cetin; Kwak, Dochan
1999-01-01
A fractional step method for the solution of steady and unsteady incompressible Navier-Stokes equations is outlined. The method is based on a finite volume formulation and uses the pressure in the cell center and the mass fluxes across the faces of each cell as dependent variables. Implicit treatment of convective and viscous terms in the momentum equations enables the numerical stability restrictions to be relaxed. The linearization error in the implicit solution of momentum equations is reduced by using three subiterations in order to achieve second order temporal accuracy for time-accurate calculations. In spatial discretizations of the momentum equations, a high-order (3rd and 5th) flux-difference splitting for the convective terms and a second-order central difference for the viscous terms are used. The resulting algebraic equations are solved with a line-relaxation scheme which allows the use of large time step. A four color ZEBRA scheme is employed after the line-relaxation procedure in the solution of the Poisson equation for pressure. This procedure is applied to a Couette flow problem using a distorted computational grid to show that the method minimizes grid effects. Additional benchmark cases include the unsteady laminar flow over a circular cylinder for Reynolds Numbers of 200, and a 3-D, steady, turbulent wingtip vortex wake propagation study. The solution algorithm does a very good job in resolving the vortex core when 5th-order upwind differencing and a modified production term in the Baldwin-Barth one-equation turbulence model are used with adequate grid resolution.
a Cell Vertex Algorithm for the Incompressible Navier-Stokes Equations on Non-Orthogonal Grids
Jessee, J. P.; Fiveland, W. A.
1996-08-01
The steady, incompressible Navier-Stokes (N-S) equations are discretized using a cell vertex, finite volume method. Quadrilateral and hexahedral meshes are used to represent two- and three-dimensional geometries respectively. The dependent variables include the Cartesian components of velocity and pressure. Advective fluxes are calculated using bounded, high-resolution schemes with a deferred correction procedure to maintain a compact stencil. This treatment insures bounded, non-oscillatory solutions while maintaining low numerical diffusion. The mass and momentum equations are solved with the projection method on a non-staggered grid. The coupling of the pressure and velocity fields is achieved using the Rhie and Chow interpolation scheme modified to provide solutions independent of time steps or relaxation factors. An algebraic multigrid solver is used for the solution of the implicit, linearized equations.A number of test cases are anlaysed and presented. The standard benchmark cases include a lid-driven cavity, flow through a gradual expansion and laminar flow in a three-dimensional curved duct. Predictions are compared with data, results of other workers and with predictions from a structured, cell-centred, control volume algorithm whenever applicable. Sensitivity of results to the advection differencing scheme is investigated by applying a number of higher-order flux limiters: the MINMOD, MUSCL, OSHER, CLAM and SMART schemes. As expected, studies indicate that higher-order schemes largely mitigate the diffusion effects of first-order schemes but also shown no clear preference among the higher-order schemes themselves with respect to accuracy. The effect of the deferred correction procedure on global convergence is discussed.
Park, Hyunwook; Pan, Xiaomin; Lee, Changhoon; Choi, Jung-Il
2016-06-01
A novel immersed boundary (IB) method based on an implicit direct forcing (IDF) scheme is developed for incompressible viscous flows. The key idea for the present IDF method is to use a block LU decomposition technique in momentum equations with Taylor series expansion to construct the implicit IB forcing in a recurrence form, which imposes more accurate no-slip boundary conditions on the IB surface. To accelerate the IB forcing convergence during the iterative procedure, a pre-conditioner matrix is introduced in the recurrence formulation of the IB forcing. A Jacobi-type parameter is determined in the pre-conditioner matrix by minimizing the Frobenius norm of the matrix function representing the difference between the IB forcing solution matrix and the pre-conditioner matrix. In addition, the pre-conditioning parameter is restricted due to the numerical stability in the recurrence formulation. Consequently, the present pre-conditioned IDF (PIDF) enables accurate calculation of the IB forcing within a few iterations. We perform numerical simulations of two-dimensional flows around a circular cylinder and three-dimensional flows around a sphere for low and moderate Reynolds numbers. The result shows that PIDF yields a better imposition of no-slip boundary conditions on the IB surfaces for low Reynolds number with a fairly larger time step than IB methods with different direct forcing schemes due to the implicit treatment of the diffusion term for determining the IB forcing. Finally, we demonstrate the robustness of the present PIDF scheme by numerical simulations of flow around a circular array of cylinders, flows around a falling sphere, and two sedimenting spheres in gravity.
Direct Numerical Simulation of Incompressible Pipe Flow Using a B-Spline Spectral Method
Loulou, Patrick; Moser, Robert D.; Mansour, Nagi N.; Cantwell, Brian J.
1997-01-01
A numerical method based on b-spline polynomials was developed to study incompressible flows in cylindrical geometries. A b-spline method has the advantages of possessing spectral accuracy and the flexibility of standard finite element methods. Using this method it was possible to ensure regularity of the solution near the origin, i.e. smoothness and boundedness. Because b-splines have compact support, it is also possible to remove b-splines near the center to alleviate the constraint placed on the time step by an overly fine grid. Using the natural periodicity in the azimuthal direction and approximating the streamwise direction as periodic, so-called time evolving flow, greatly reduced the cost and complexity of the computations. A direct numerical simulation of pipe flow was carried out using the method described above at a Reynolds number of 5600 based on diameter and bulk velocity. General knowledge of pipe flow and the availability of experimental measurements make pipe flow the ideal test case with which to validate the numerical method. Results indicated that high flatness levels of the radial component of velocity in the near wall region are physical; regions of high radial velocity were detected and appear to be related to high speed streaks in the boundary layer. Budgets of Reynolds stress transport equations showed close similarity with those of channel flow. However contrary to channel flow, the log layer of pipe flow is not homogeneous for the present Reynolds number. A topological method based on a classification of the invariants of the velocity gradient tensor was used. Plotting iso-surfaces of the discriminant of the invariants proved to be a good method for identifying vortical eddies in the flow field.
Kuehn, Donald M.
1980-01-01
The turbulent, incompressible reattaching flow over a rearward-facing step has been studied by many researchers over the years. One of the principal quantities determined in these experiments has been the distance from the step to the point (or region) where the separated shear layer reattaches to the surface (x(r)). The values for x(r)/h, where h is the step height, have covered a wider range than can reasonably be attributed to experimental technique or inaccuracy. Often the reason for a largely different value of x(r)/h can be attributed to an incompletely developed turbulent layer, or a transitional or laminar boundary layer. However, for the majority of experiments where the boundary layer is believed to be fully developed and turbulent, x(r)/h still varies several step heights; generally, 5 1/2 approximately step length to height, h/delta (step height to initial boundary-layer thickness), R(e)(theta)), or the experimental technique for determining reattachment location. However, there are so many different combinations of variables in the previous experiments that it was not possible to sort out the effects of particular conditions on the location of reattachment. In the present experiment velocity profiles have been measured in and around the region of separated flow. Results show a large influence of adverse pressure gradient on the reattaching flow over a rearward-facing step that has not been reported previously. Further, the many previous experiments for fully developed, turbulent flow in parallel-walled channels have shown a range of reattachment location that has not been explained by differences in initial flow conditions. Although these initial flow conditions might contribute to the observed variation of reattachment location, it appears that the pressure gradient effect can explain most of that variation.
Halas, John
Visual scripting is the coordination of words with pictures in sequence. This book presents the methods and viewpoints on visual scripting of fourteen film makers, from nine countries, who are involved in animated cinema; it contains concise examples of how a storybook and preproduction script can be prepared in visual terms; and it includes a…
Azzam, Tarek
2013-01-01
Do you communicate data and information to stakeholders? In Part 1, we introduce recent developments in the quantitative and qualitative data visualization field and provide a historical perspective on data visualization, its potential role in evaluation practice, and future directions. Part 2 delivers concrete suggestions for optimally using data visualization in evaluation, as well as suggestions for best practices in data visualization design. It focuses on specific quantitative and qualitative data visualization approaches that include data dashboards, graphic recording, and geographic information systems (GIS). Readers will get a step-by-step process for designing an effective data dashboard system for programs and organizations, and various suggestions to improve their utility.
Álvarez, R; Masjuan, J
2016-03-01
Visual agnosia is defined as an impairment of object recognition, in the absence of visual acuity or cognitive dysfunction that would explain this impairment. This condition is caused by lesions in the visual association cortex, sparing primary visual cortex. There are 2 main pathways that process visual information: the ventral stream, tasked with object recognition, and the dorsal stream, in charge of locating objects in space. Visual agnosia can therefore be divided into 2 major groups depending on which of the two streams is damaged. The aim of this article is to conduct a narrative review of the various visual agnosia syndromes, including recent developments in a number of these syndromes. Copyright © 2015 Elsevier España, S.L.U. y Sociedad Española de Medicina Interna (SEMI). All rights reserved.
Directory of Open Access Journals (Sweden)
Dr. G. Prabhakara Rao,
2015-04-01
Full Text Available We consider a two-dimensional MHD natural convection flow of an incompressible viscous and electrically conducting fluid through porous medium past a vertical impermeable flat plate is considered in presence of a uniform transverse magnetic field. The governing equations of velocity and temperature fields with appropriate boundary conditions are solved by the ordinary differential equations by introducing appropriate coordinate transformations. We solve that ordinary differential equations and find the velocity profiles, temperature profile, the skin friction and nusselt number. The effects of Grashof number (Gr, Hartmann number (M and Prandtl number (Pr, Darcy parameter (D-1 on velocity profiles and temperature profiles are shown graphically.
Mukherjee, Soumyajit; Biswas, Rakesh
2014-03-01
We present preliminary kinematic analyses of Taylor-Couette flow. We consider deformation of a Newtonian incompressible ductile material inside rotating horizontal listric (concentric circular) boundaries. The velocity profile is curved indicating non-uniform shear strain but leads to the same shear sense. Each material point on progressive shear keeps increasing shear strain linearly with time. A curve of no movement, the `neutral curve', may exist inside the shear zone. Irregular geometries of initially regular markers and their individual non-matching strain paths indicate inhomogeneous deformaion in such Taylor-Couette flow.
Directory of Open Access Journals (Sweden)
Svetlana S. Vlasova
2016-09-01
Full Text Available The exact stationary solution of the boundary-value problem that describes the convective motion of an incompressible viscous fluid in the two-dimensional layer with the square heating of a free surface in Stokes's approach is found. The linearization of the Oberbeck–Boussinesq equations allows one to describe the flow of fluid in extreme points of pressure and temperature. The condition under which the counter-current flows (two counter flows in the fluid can be observed, is introduced. If the stagnant point in the fluid exists, six non-closed whirlwinds can be observed.
Sohn, Jeong L.
1988-01-01
The purpose of the study is the evaluation of the numerical accuracy of FIDAP (Fluid Dynamics Analysis Package). Accordingly, four test problems in laminar and turbulent incompressible flows are selected and the computational results of these problems compared with other numerical solutions and/or experimental data. These problems include: (1) 2-D laminar flow inside a wall-driven cavity; (2) 2-D laminar flow over a backward-facing step; (3) 2-D turbulent flow over a backward-facing step; and (4) 2-D turbulent flow through a turn-around duct.
Guermond, Jean-Luc
2010-05-01
A new direction-splitting-based fractional time stepping is introduced for solving the incompressible Navier-Stokes equations. The main originality of the method is that the pressure correction is computed by solving a sequence of one-dimensional elliptic problems in each spatial direction. The method is very simple to program in parallel, very fast, and has exactly the same stability and convergence properties as the Poisson-based pressure-correction technique, either in standard or rotational form. © 2010 Académie des sciences.
Directory of Open Access Journals (Sweden)
Ping Liu
2015-08-01
Full Text Available The symmetry reduction equations, similarity solutions, sub-groups and exact solutions of the (3+1-dimensional nonlinear incompressible non-hydrostatic Boussinesq equations with viscosity (INHBV equations, which describe the atmospheric gravity waves, are researched in this paper. Calculation on symmetry shows that the equations are invariant under the Galilean transformations, scaling transformations, rotational transformations and space-time translations. Three types of symmetry reduction equations and similar solutions for the (3+1-dimensional INHBV equations are proposed. Traveling wave solutions of the INHBV equations are demonstrated by means of symmetry method. The evolutions on the wind velocities and temperature perturbation are demonstrated by figures.
Zeng, S.; Wesseling, P.
1993-01-01
The performance of a linear multigrid method using four smoothing methods, called SCGS (Symmetrical Coupled GauBeta-Seidel), CLGS (Collective Line GauBeta-Seidel), SILU (Scalar ILU), and CILU (Collective ILU), is investigated for the incompressible Navier-Stokes equations in general coordinates, in association with Galerkin coarse grid approximation. Robustness and efficiency are measured and compared by application to test problems. The numerical results show that CILU is the most robust, SILU the least, with CLGS and SCGS in between. CLGS is the best in efficiency, SCGS and CILU follow, and SILU is the worst.
Energy Technology Data Exchange (ETDEWEB)
Martin, D.F.; Colella, P.; Graves, D.T.
2007-09-25
We present a method for computing incompressible viscousflows in three dimensions using block-structured local refinement in bothspace and time. This method uses a projection formulation based on acell-centered approximate projection, combined with the systematic use ofmultilevel elliptic solvers to compute increments in the solutiongenerated at boundaries between refinement levels due to refinement intime. We use an L_0-stable second-order semi-implicit scheme to evaluatethe viscous terms. Results are presentedto demonstrate the accuracy andeffectiveness of this approach.
Maity, Debayan; Raymond, Jean-Pierre
2017-12-01
In this article we study a system coupling the incompressible Navier-Stokes equations with an elastic structure governed by a damped wave equation in a two dimensional channel with periodic boundary conditions. The elastic structure is located at the upper boundary of the domain occupied by the fluid. The domain occupied by the fluid depends on the displacement of the elastic structure, and therefore it depends on time. We prove that this coupled system may be stabilized around the steady state zero, at any exponential decay rate, by a Dirichlet control acting in the lower boundary of the fluid domain.
Directory of Open Access Journals (Sweden)
Boričić Zoran
2005-01-01
Full Text Available This paper deals with laminar, unsteady flow of viscous, incompressible and electro conductive fluid caused by variable motion of flat plate. Fluid electro conductivity is variable. Velocity of the plate is time function. Plate moves in its own plane and in "still" fluid. Present external magnetic filed is perpendicular to the plate. Plate temperature is a function of longitudinal coordinate and time. Viscous dissipation, Joule heat, Hole and polarization effects are neglected. For obtaining of universal equations system general similarity method is used as well as impulse and energy equation of described problem.
A finite-volume, incompressible Navier Stokes model for studies of the ocean on parallel computers
Marshall, John; Adcroft, Alistair; Hill, Chris; Perelman, Lev; Heisey, Curt
1997-03-01
The numerical implementation of an ocean model based on the incompressible Navier Stokes equations which is designed for studies of the ocean circulation on horizontal scales less than the depth of the ocean right up to global scale is described. A "pressure correction" method is used which is solved as a Poisson equation for the pressure field with Neumann boundary conditions in a geometry as complicated as that of the ocean basins. A major objective of the study is to make this inversion, and hence nonhydrostatic ocean modeling, efficient on parallel computers. The pressure field is separated into surface, hydrostatic, and nonhydrostatic components. First, as in hydrostatic models, a two-dimensional problem is inverted for the surface pressure which is then made use of in the three-dimensional inversion for the nonhydrostatic pressure. Preconditioned conjugate-gradient iteration is used to invert symmetric elliptic operators in both two and three dimensions. Physically motivated preconditioners are designed which are efficient at reducing computation and minimizing communication between processors. Our method exploits the fact that as the horizontal scale of the motion becomes very much larger than the vertical scale, the motion becomes more and more hydrostatic and the three-dimensional Poisson operator becomes increasingly anisotropic and dominated by the vertical axis. Accordingly, a preconditioner is used which, in the hydrostatic limit, is an exact integral of the Poisson operator and so leads to a single algorithm that seamlessly moves from nonhydrostatic to hydrostatic limits. Thus in the hydrostatic limit the model is "fast," competitive with the fastest ocean climate models in use today based on the hydrostatic primitive equations. But as the resolution is increased, the model dynamics asymptote smoothly to the Navier Stokes equations and so can be used to address small-scale processes. A "finite-volume" approach is employed to discretize the model in
Angelidis, Dionysios; Chawdhary, Saurabh; Sotiropoulos, Fotis
2016-11-01
A novel numerical method is developed for solving the 3D, unsteady, incompressible Navier-Stokes equations on locally refined fully unstructured Cartesian grids in domains with arbitrarily complex immersed boundaries. Owing to the utilization of the fractional step method on an unstructured Cartesian hybrid staggered/non-staggered grid layout, flux mismatch and pressure discontinuity issues are avoided and the divergence free constraint is inherently satisfied to machine zero. Auxiliary/hanging nodes are used to facilitate the discretization of the governing equations. The second-order accuracy of the solver is ensured by using multi-dimension Lagrange interpolation operators and appropriate differencing schemes at the interface of regions with different levels of refinement. The sharp interface immersed boundary method is augmented with local near-boundary refinement to handle arbitrarily complex boundaries. The discrete momentum equation is solved with the matrix free Newton-Krylov method and the Krylov-subspace method is employed to solve the Poisson equation. The second-order accuracy of the proposed method on unstructured Cartesian grids is demonstrated by solving the Poisson equation with a known analytical solution. A number of three-dimensional laminar flow simulations of increasing complexity illustrate the ability of the method to handle flows across a range of Reynolds numbers and flow regimes. Laminar steady and unsteady flows past a sphere and the oblique vortex shedding from a circular cylinder mounted between two end walls demonstrate the accuracy, the efficiency and the smooth transition of scales and coherent structures across refinement levels. Large-eddy simulation (LES) past a miniature wind turbine rotor, parameterized using the actuator line approach, indicates the ability of the fully unstructured solver to simulate complex turbulent flows. Finally, a geometry resolving LES of turbulent flow past a complete hydrokinetic turbine illustrates
Huron, Samuel; Vuillemot, Romain; Fekete, Jean-Daniel
2013-01-01
International audience; We introduce Visual Sedimentation, a novel design metaphor for visualizing data streams directly inspired by the physical process of sedimentation. Visualizing data streams (e. g., Tweets, RSS, Emails) is challenging as incoming data arrive at unpredictable rates and have to remain readable. For data streams, clearly expressing chronological order while avoiding clutter, and keeping aging data visible, are important. The metaphor is drawn from the real-world sedimentat...
Federal Laboratory Consortium — FUNCTION: Evaluates and improves the operational effectiveness of existing and emerging electronic warfare systems. By analyzing and visualizing simulation results...
Directory of Open Access Journals (Sweden)
Ivanović Dečan
2005-01-01
Full Text Available Through the porous contour in perpendicular direction, the fluid of the same properties as incompressible fluid in basic flow, has been injected or ejected with velocity who is a function of the contour longitudinal coordinate and time. The corresponding equations of unsteady boundary layer, by introducing the appropriate variable transformations, momentum and energy equations and two similarity parameters sets, are transformed into generalized form. These parameters are expressing the influence of the outer flow velocity, the injection or ejection velocity and the flow history in boundary layer, on the boundary layer characteristics. Obtained generalized solutions are used to calculate the distributions of velocity, and shear stress in laminar-turbulent transition of unsteady incompressible boundary layer on different porous contours: circular cylinder, thin elliptical cylinder and aerofoil, whose centers velocities changes in time as a degree functions. The ejection of fluid postpones the boundary layer separation, i.e. laminar-turbulent transition, and vice versa the injection of fluid favors the separation. Boundary layer characteristics are found directly, no further numerical integration of momentum equation.
Energy Technology Data Exchange (ETDEWEB)
Richard C. Martineau; Ray A. Berry; Aurélia Esteve; Kurt D. Hamman; Dana A. Knoll; Ryosuke Park; William Taitano
2009-01-01
This report illustrates a comparative study to analyze the physical differences between numerical simulations obtained with both the conservation and incompressible forms of the Navier-Stokes equations for natural convection flows in simple geometries. The purpose of this study is to quantify how the incompressible flow assumption (which is based upon constant density advection, divergence-free flow, and the Boussinesq gravitational body force approximation) differs from the conservation form (which only assumes that the fluid is a continuum) when solving flows driven by gravity acting upon density variations resulting from local temperature gradients. Driving this study is the common use of the incompressible flow assumption in fluid flow simulations for nuclear power applications in natural convection flows subjected to a high heat flux (large temperature differences). A series of simulations were conducted on two-dimensional, differentially-heated rectangular geometries and modeled with both hydrodynamic formulations. From these simulations, the selected characterization parameters of maximum Nusselt number, average Nusselt number, and normalized pressure reduction were calculated. Comparisons of these parameters were made with available benchmark solutions for air with the ideal gas assumption at both low and high heat fluxes. Additionally, we generated body force, velocity, and divergence of velocity distributions to provide a basis for further analysis. The simulations and analysis were then extended to include helium at the Very High Temperature gas-cooled Reactor (VHTR) normal operating conditions. Our results show that the consequences of incorporating the incompressible flow assumption in high heat flux situations may lead to unrepresentative results. The results question the use of the incompressible flow assumption for simulating fluid flow in an operating nuclear reactor, where large temperature variations are present. The results show that the use of
Toet, A.; Bijl, P.
2003-01-01
Visual search, with or without the aid of optical or electro-optical instruments, plays a significant role in various types of military and civilian operations (e.g., reconnaissance, surveillance, and search and rescue). Advance knowledge of human visual search and target acquisition performance is
Energy Technology Data Exchange (ETDEWEB)
NONE
1980-03-01
Examination was conducted in detail on an MHD generation system by coal combustion, with the results reported. Concerning a gas table calculation program in coal combustion, it was prepared assuming 100% slag removal ratio in the combustor as the primary approximation. A combustor for MHD generation needs to efficiently burn fuel using high temperature pre-heated air as the oxidant, to fully dissociate/electrolytically dissociate seed, and to supply to the generation channel a high speed combustion gas plasma having a high electrical conductivity which is required for MHD generation. This year, an examination was conducted on technological problems in burning coal in an MHD combustor. As for the NOx elimination system in an MHD generation plant, an examination was made if the method studied so far in MHD generation using heavy oil as the fuel is applicable to coal. Also investigated and reviewed were various characteristics, change in physical properties, recovery method, etc., in a mixed state of seed and slag in the case of coal combustion MHD. (NEDO)
Directory of Open Access Journals (Sweden)
M. Merikhi
2015-10-01
Full Text Available In this paper, the effect of magnetic field on the morphology, structure and magnetic properties of electrodeposited FeCu/Cu thin films was investigated. The films were deposited on Au2PdAg/glass substrates using electrodeposition technique in potentiostatic control. The magnetic fields of 5000 and 7000 Oe were applied on deposition bath during deposition. Two series of thin films were prepared in the same deposition conditions, one in the presence and the other in absence of magnetic field and the products were compared. The results indicate that applying the magnetic field has a significant effect on the growth process, i.e. morphology, crystal structure and magnetic properties of the films. The morphology and structure of the FeCu/Cu Nano layers were studied using X-ray diffraction (XRD and scanning electron microscopy (SEM. The weight percentages of the elements in the deposited multilayers were determined by energy dispersive X-ray spectroscopy (EDS. Magnetic properties of thin films were studied using the vibrating sample magnetometer (VSM.
DEFF Research Database (Denmark)
Comminal, Raphaël; Spangenberg, Jon; Hattel, Jesper Henri
of the flow. Contrary to fractional step methods, the streamfunction formulation eliminates the pressure unknowns, and automatically fulfills the incompressibility constraint by construction. As a result, the method circumvents the loss of temporal accuracy at low Reynolds numbers. The interface is tracked......Accurate multi-phase flow solvers at low Reynolds number are of particular interest for the simulation of interface instabilities in the co-processing of multilayered material. We present a two-phase flow solver for incompressible viscous fluids which uses the streamfunction as the primary variable...
DEFF Research Database (Denmark)
Comminal, Raphaël; Spangenberg, Jon; Hattel, Jesper Henri
2014-01-01
of the flow. Contrary to fractional step methods, the streamfunction formulation eliminates the pressure unknowns, and automatically fulfills the incompressibility constraint by construction. As a result, the method circumvents the loss of temporal accuracy at low Reynolds numbers. The interface is tracked......Accurate multi-phase flow solvers at low Reynolds number are of particular interest for the simulation of interface instabilities in the co-processing of multilayered material. We present a two-phase flow solver for incompressible viscous fluids which uses the streamfunction as the primary variable...
DEFF Research Database (Denmark)
Buhl, Mie; Flensborg, Ingelise
2010-01-01
The intrinsic breadth of various types of images creates new possibilities and challenges for visual education. The digital media have moved the boundaries between images and other kinds of modalities (e.g. writing, speech and sound) and have augmented the possibilities for integrating the functi......The intrinsic breadth of various types of images creates new possibilities and challenges for visual education. The digital media have moved the boundaries between images and other kinds of modalities (e.g. writing, speech and sound) and have augmented the possibilities for integrating...... to emerge in the interlocutory space of a global visual repertoire and diverse local interpretations. The two perspectives represent challenges for future visual education which require visual competences, not only within the arts but also within the subjects of natural sciences, social sciences, languages...
Cavanagh, Patrick
2011-07-01
Visual cognition, high-level vision, mid-level vision and top-down processing all refer to decision-based scene analyses that combine prior knowledge with retinal input to generate representations. The label "visual cognition" is little used at present, but research and experiments on mid- and high-level, inference-based vision have flourished, becoming in the 21st century a significant, if often understated part, of current vision research. How does visual cognition work? What are its moving parts? This paper reviews the origins and architecture of visual cognition and briefly describes some work in the areas of routines, attention, surfaces, objects, and events (motion, causality, and agency). Most vision scientists avoid being too explicit when presenting concepts about visual cognition, having learned that explicit models invite easy criticism. What we see in the literature is ample evidence for visual cognition, but few or only cautious attempts to detail how it might work. This is the great unfinished business of vision research: at some point we will be done with characterizing how the visual system measures the world and we will have to return to the question of how vision constructs models of objects, surfaces, scenes, and events. Copyright © 2011 Elsevier Ltd. All rights reserved.
Cavanagh, Patrick
2011-01-01
Visual cognition, high-level vision, mid-level vision and top-down processing all refer to decision-based scene analyses that combine prior knowledge with retinal input to generate representations. The label “visual cognition” is little used at present, but research and experiments on mid- and high-level, inference-based vision have flourished, becoming in the 21st century a significant, if often understated part, of current vision research. How does visual cognition work? What are its moving...
Mamassian, Pascal
2016-10-14
Visual confidence refers to an observer's ability to judge the accuracy of her perceptual decisions. Even though confidence judgments have been recorded since the early days of psychophysics, only recently have they been recognized as essential for a deeper understanding of visual perception. The reluctance to study visual confidence may have come in part from obtaining convincing experimental evidence in favor of metacognitive abilities rather than just perceptual sensitivity. Some effort has thus been dedicated to offer different experimental paradigms to study visual confidence in humans and nonhuman animals. To understand the origins of confidence judgments, investigators have developed two competing frameworks. The approach based on signal decision theory is popular but fails to account for response times. In contrast, the approach based on accumulation of evidence models naturally includes the dynamics of perceptual decisions. These models can explain a range of results, including the apparently paradoxical dissociation between performance and confidence that is sometimes observed.
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Pinker, S.
1985-01-01
This book consists of essays covering issues in visual cognition presenting experimental techniques from cognitive psychology, methods of modeling cognitive processes on computers from artificial intelligence, and methods of studying brain organization from neuropsychology. Topics considered include: parts of recognition; visual routines; upward direction; mental rotation, and discrimination of left and right turns in maps; individual differences in mental imagery, computational analysis and the neurological basis of mental imagery: componental analysis.
Kroon, M.
2011-11-01
Rubbers and soft biological tissues may undergo large deformations and are also viscoelastic. The formulation of constitutive models for these materials poses special challenges. In several applications, especially in biomechanics, these materials are also relatively thin, implying that in-plane stresses dominate and that plane stress may therefore be assumed. In the present paper, a constitutive model for viscoelastic materials in the finite strain regime and under the assumption of plane stress is proposed. It is assumed that the relaxation behaviour in the direction of plane stress can be treated separately, which makes it possible to formulate evolution laws for the plastic strains on explicit form at the same time as incompressibility is fulfilled. Experimental results from biomechanics (dynamic inflation of dog aorta) and rubber mechanics (biaxial stretching of rubber sheets) were used to assess the proposed model. The assessment clearly indicates that the model is fully able to predict the experimental outcome for these types of material.
Directory of Open Access Journals (Sweden)
A. D. Pataraya
1997-01-01
Full Text Available Non-linear α-ω; dynamo waves existing in an incompressible medium with the turbulence dissipative coefficients depending on temperature are studied in this paper. We investigate of α-ω solar non-linear dynamo waves when only the first harmonics of magnetic induction components are included. If we ignore the second harmonics in the non-linear equation, the turbulent magnetic diffusion coefficient increases together with the temperature, the coefficient of turbulent viscosity decreases, and for an interval of time the value of dynamo number is greater than 1. In these conditions a stationary solution of the non-linear equation for the dynamo wave's amplitude exists; meaning that the magnetic field is sufficiently excited. The amplitude of the dynamo waves oscillates and becomes stationary. Using these results we can explain the existence of Maunder's minimum.
Directory of Open Access Journals (Sweden)
Zakurdaeva Alia
2016-01-01
Full Text Available The results of mathematical modelling of the dynamics of a mixture of the viscous incompressible liquid and gas, which fills a spherical layer with free boundaries and contains a gas bubble within itself, are presented in this paper. Spherical symmetry is assumed, and it is considered that the dynamics of the layer is determined by thermal, diffusive and inertial factors. On the basis of constructed numerical algorithm the studies of the formation of the liquid glass layers, which contain the carbon dioxide gas within themselves, have been conducted. The impact of the external thermal regime, external pressure and the density of gas in the bubble at the initial time on the dynamics of the layer, diffusion and heat-and-mass processes inside it is investigated. The results of numerical investigation of the full and simplified thermal problem statement, without consideration of gas diffusion, are compared.
Felderhof, B U
2016-01-01
Translational and rotational swimming at small Reynolds number of a planar assembly of identical spheres immersed in an incompressible viscous fluid is studied on the basis of a set of equations of motion for the individual spheres. The motion of the spheres is caused by actuating forces and forces derived from a direct interaction potential, as well as hydrodynamic forces exerted by the fluid as frictional and added mass hydrodynamic interactions. The translational and rotational swimming velocities of the assembly are deduced from momentum and angular momentum balance equations. The mean power required during a period is calculated from an instantaneous power equation. Expressions are derived for the mean swimming velocities and the power, valid to second order in the amplitude of displacements from the relative equilibrium positions. Hence these quantities can be evaluated for prescribed periodic displacements. Explicit calculations are performed for three spheres interacting such that they form an equilat...
Rosenfeld, Moshe; Kwak, Dochan; Vinokur, Marcel
1991-01-01
The time-dependent, three-dimensional incompressible Navier-Stokes equations are presently solved in generalized coordinate systems by means of a fractional-step method whose primitive variable formulation uses as dependent variables, in place of the Cartesian components of the velocity: (1) pressure (defined at the center of the computational cell), and (2) volume fluxes across the faces of the cells. The momentum equations are solved by means of an approximate factorization method. A novel 'ZEBRA' scheme incorporating four-color ordering efficiently solves the Poisson equation. Illustrative two- and three-dimensional laminar flow test cases are computed and evaluated relative to extant numerical and experimental results, and good agreement is obtained.
Directory of Open Access Journals (Sweden)
Xing Zheng
2017-06-01
Full Text Available The Smoothed Particle Hydrodynamics (SPH method has proven to have great potential in dealing with the wave–structure interactions since it can deal with the large amplitude and breaking waves and easily captures the free surface. The paper will adopt an incompressible SPH (ISPH approach to simulate the wave propagation and impact, in which the fluid pressure is solved using a pressure Poisson equation and thus more stable and accurate pressure fields can be obtained. The focus of the study is on comparing three different pressure gradient calculation models in SPH and proposing the most efficient first-order consistent kernel interpolation (C1_KI numerical scheme for modelling violent wave impact. The improvement of the model is validated by the benchmark dam break flows and laboratory wave propagation and impact experiments.
Felderhof, B. U.
2017-09-01
Translational and rotational swimming at small Reynolds numbers of a planar assembly of identical spheres immersed in an incompressible viscous fluid is studied on the basis of a set of equations of motion for the individual spheres. The motion of the spheres is caused by actuating forces and forces derived from a direct interaction potential, as well as hydrodynamic forces exerted by the fluid as frictional and added mass hydrodynamic interactions. The translational and rotational swimming velocities of the assembly are deduced from momentum and angular momentum balance equations. The mean power required during a period is calculated from an instantaneous power equation. Expressions are derived for the mean swimming velocities and the mean power, valid to second order in the amplitude of displacements from the relative equilibrium positions. Hence these quantities can be evaluated for prescribed periodic displacements. Explicit calculations are performed for three spheres interacting such that they form an equilateral triangle in the rest frame of the configuration.
Alessia, Berti; Bochicchio, Ivana; Fabrizio, Mauro
2015-02-01
In this paper, we propose a mathematical model of phase separation for a quasi-incompressible binary mixture where the spinodal decomposition is induced by an heat flux governed by the Cattaneo-Maxwell equation. As usual, the phase separation is considered in the framework of phase-field modeling so that the transition is described by an additional field, the mixture concentration c. The evolution of the mixture concentration is described by the Cahn-Hilliard equation, and in our model, it is coupled with the Navier-Stokes equation. Since thermal effect is included, the whole set of evolution equations is set up for the velocity, the mixture concentration, the temperature and the heat flux. The model is compatible with thermodynamics and a maximum theorem holds.
Wang, Ya-Guang; Yin, Jierong; Zhu, Shiyong
2017-10-01
In this paper, we will analyze the vanishing viscosity limit of the incompressible Navier-Stokes equations with the Navier slip boundary conditions in a bounded domain of R2. When the slip length is smaller than or equal to the order of viscosity, by using an energy method and developing Kato's approach given in the work of Kato [Math. Sci. Res. Inst. Publ. 2, 85-98 (1984)], we obtain several conditions to guarantee that the solution of the Navier-Stokes equations with the Navier slip boundary conditions goes to the solution of the associated problem of the Euler equations in the energy space L2 uniformly in time, as the viscosity goes to zero.
Kou, Jisheng
2014-03-22
Discontinuous Galerkin methods with interior penalties and upwind schemes are applied to the original formulation modeling incompressible two-phase flow in porous media with the capillary pressure. The pressure equation is obtained by summing the discretized conservation equations of two phases. This treatment is very different from the conventional approaches, and its great merit is that the mass conservations hold for both phases instead of only one phase in the conventional schemes. By constructing a new continuous map and using the fixed-point theorem, we prove the global existence of discrete solutions under the proper conditions, and furthermore, we obtain a priori hp error estimates of the pressures in L 2 (H 1) and the saturations in L ∞(L 2) and L 2 (H 1). © 2014 Wiley Periodicals, Inc.
Chen, Huangxin
2017-09-01
In this paper we consider the energy stability estimates for some fully discrete schemes which both consider time and spatial discretizations for the incompressible Navier–Stokes equations. We focus on three kinds of fully discrete schemes, i.e., the linear implicit scheme for time discretization with the finite difference method (FDM) on staggered grids for spatial discretization, pressure-correction schemes for time discretization with the FDM on staggered grids for the solutions of the decoupled velocity and pressure equations, and pressure-stabilization schemes for time discretization with the FDM on staggered grids for the solutions of the decoupled velocity and pressure equations. The energy stability estimates are obtained for the above each fully discrete scheme. The upwind scheme is used in the discretization of the convection term which plays an important role in the design of unconditionally stable discrete schemes. Numerical results are given to verify the theoretical analysis.
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Reza Hosseini
2012-01-01
Full Text Available The flow of an incompressible electrically conducting viscous fluid in convergent or divergent channels under the influence of an externally applied homogeneous magnetic field is studied both analytically and numerically. Navier-Stokes equations of fluid mechanics and Maxwell’s electromagnetism equations are reduced into highly non-linear ordinary differential equation. The resulting non-linear equation has been solved analytically using a very efficient technique, namely, differential transform method (DTM. The DTM solution is compared with the results obtained by a numerical method (shooting method, coupled with fourth-order Runge-Kutta scheme. The plots have revealed the physical characteristics of flow by changing angles of the channel, Hartmann and Reynolds numbers.
DEFF Research Database (Denmark)
Christensen, Max la Cour; Villa, Umberto; Engsig-Karup, Allan Peter
2017-01-01
We study the application of a finite element numerical upscaling technique to the incompressible two-phase porous media total velocity formulation. Specifically, an element agglomeration based Algebraic Multigrid (AMGe) technique with improved approximation proper ties [37] is used, for the first...... associated with non-planar interfaces between agglomerates, the coarse velocity space has guaranteed approximation properties. The employed AMGe technique provides coarse spaces with desirable local mass conservation and stability properties analogous to the original pair of Raviart-Thomas and piecewise...... and unstructured meshes. Multiscale Mixed Finite Elements exhibit accuracy for general unstructured meshes but do not in general lead to nested hierarchy of spaces. Multiscale multilevel mimetic finite differences generate nested spaces but lack the adaptivity of the flux representation on coarser levels...
Ha, Sanghyun; Park, Junshin; You, Donghyun
2018-01-01
Utility of the computational power of Graphics Processing Units (GPUs) is elaborated for solutions of incompressible Navier-Stokes equations which are integrated using a semi-implicit fractional-step method. The Alternating Direction Implicit (ADI) and the Fourier-transform-based direct solution methods used in the semi-implicit fractional-step method take advantage of multiple tridiagonal matrices whose inversion is known as the major bottleneck for acceleration on a typical multi-core machine. A novel implementation of the semi-implicit fractional-step method designed for GPU acceleration of the incompressible Navier-Stokes equations is presented. Aspects of the programing model of Compute Unified Device Architecture (CUDA), which are critical to the bandwidth-bound nature of the present method are discussed in detail. A data layout for efficient use of CUDA libraries is proposed for acceleration of tridiagonal matrix inversion and fast Fourier transform. OpenMP is employed for concurrent collection of turbulence statistics on a CPU while the Navier-Stokes equations are computed on a GPU. Performance of the present method using CUDA is assessed by comparing the speed of solving three tridiagonal matrices using ADI with the speed of solving one heptadiagonal matrix using a conjugate gradient method. An overall speedup of 20 times is achieved using a Tesla K40 GPU in comparison with a single-core Xeon E5-2660 v3 CPU in simulations of turbulent boundary-layer flow over a flat plate conducted on over 134 million grids. Enhanced performance of 48 times speedup is reached for the same problem using a Tesla P100 GPU.
Energy Technology Data Exchange (ETDEWEB)
Williams, P. T. [Univ. of Tennessee, Knoxville, TN (United States)
1993-09-01
As the field of computational fluid dynamics (CFD) continues to mature, algorithms are required to exploit the most recent advances in approximation theory, numerical mathematics, computing architectures, and hardware. Meeting this requirement is particularly challenging in incompressible fluid mechanics, where primitive-variable CFD formulations that are robust, while also accurate and efficient in three dimensions, remain an elusive goal. This dissertation asserts that one key to accomplishing this goal is recognition of the dual role assumed by the pressure, i.e., a mechanism for instantaneously enforcing conservation of mass and a force in the mechanical balance law for conservation of momentum. Proving this assertion has motivated the development of a new, primitive-variable, incompressible, CFD algorithm called the Continuity Constraint Method (CCM). The theoretical basis for the CCM consists of a finite-element spatial semi-discretization of a Galerkin weak statement, equal-order interpolation for all state-variables, a 0-implicit time-integration scheme, and a quasi-Newton iterative procedure extended by a Taylor Weak Statement (TWS) formulation for dispersion error control. Original contributions to algorithmic theory include: (a) formulation of the unsteady evolution of the divergence error, (b) investigation of the role of non-smoothness in the discretized continuity-constraint function, (c) development of a uniformly H^{1} Galerkin weak statement for the Reynolds-averaged Navier-Stokes pressure Poisson equation, (d) derivation of physically and numerically well-posed boundary conditions, and (e) investigation of sparse data structures and iterative methods for solving the matrix algebra statements generated by the algorithm.
Energy Technology Data Exchange (ETDEWEB)
Lemos, Jose P.S.; Lopes, Francisco J.; Quinta, Goncalo [Universidade de Lisboa, UL, Departamento de Fisica, Centro Multidisciplinar de Astrofisica, CENTRA, Instituto Superior Tecnico, IST, Lisbon (Portugal); Zanchin, Vilson T. [Universidade Federal do ABC, Centro de Ciencias Naturais e Humanas, Santo Andre, SP (Brazil)
2015-02-01
One of the stiffest equations of state for matter in a compact star is constant energy density and this generates the interior Schwarzschild radius to mass relation and the Misner maximum mass for relativistic compact stars. If dark matter populates the interior of stars, and this matter is supersymmetric or of some other type, some of it possessing a tiny electric charge, there is the possibility that highly compact stars can trap a small but non-negligible electric charge. In this case the radius to mass relation for such compact stars should get modifications. We use an analytical scheme to investigate the limiting radius to mass relation and the maximum mass of relativistic stars made of an incompressible fluid with a small electric charge. The investigation is carried out by using the hydrostatic equilibrium equation, i.e., the Tolman-Oppenheimer-Volkoff (TOV) equation, together with the other equations of structure, with the further hypothesis that the charge distribution is proportional to the energy density. The approach relies on Volkoff and Misner's method to solve the TOV equation. For zero charge one gets the interior Schwarzschild limit, and supposing incompressible boson or fermion matter with constituents with masses of the order of the neutron mass one finds that the maximum mass is the Misner mass. For a small electric charge, our analytical approximating scheme, valid in first order in the star's electric charge, shows that the maximum mass increases relatively to the uncharged case, whereas the minimum possible radius decreases, an expected effect since the new field is repulsive, aiding the pressure to sustain the star against gravitational collapse. (orig.)
Baart, F.; van Gils, A.; Hagenaars, G.; Donchyts, G.; Eisemann, E.; van Velzen, J. W.
2016-12-01
A compelling visualization is captivating, beautiful and narrative. Here we show how melding the skills of computer graphics, art, statistics, and environmental modeling can be used to generate innovative, attractive and very informative visualizations. We focus on the topic of visualizing forecasts and measurements of water (water level, waves, currents, density, and salinity). For the field of computer graphics and arts, water is an important topic because it occurs in many natural scenes. For environmental modeling and statistics, water is an important topic because the water is essential for transport, a healthy environment, fruitful agriculture, and a safe environment.The different disciplines take different approaches to visualizing water. In computer graphics, one focusses on creating water as realistic looking as possible. The focus on realistic perception (versus the focus on the physical balance pursued by environmental scientists) resulted in fascinating renderings, as seen in recent games and movies. Visualization techniques for statistical results have benefited from the advancement in design and journalism, resulting in enthralling infographics. The field of environmental modeling has absorbed advances in contemporary cartography as seen in the latest interactive data-driven maps. We systematically review the design emerging types of water visualizations. The examples that we analyze range from dynamically animated forecasts, interactive paintings, infographics, modern cartography to web-based photorealistic rendering. By characterizing the intended audience, the design choices, the scales (e.g. time, space), and the explorability we provide a set of guidelines and genres. The unique contributions of the different fields show how the innovations in the current state of the art of water visualization have benefited from inter-disciplinary collaborations.
Low-Order Modeling of Dynamic Stall on Airfoils in Incompressible Flow
Narsipur, Shreyas
Unsteady aerodynamics has been a topic of research since the late 1930's and has increased in popularity among researchers studying dynamic stall in helicopters, insect/bird flight, micro air vehicles, wind-turbine aerodynamics, and ow-energy harvesting devices. Several experimental and computational studies have helped researchers gain a good understanding of the unsteady ow phenomena, but have proved to be expensive and time-intensive for rapid design and analysis purposes. Since the early 1970's, the push to develop low-order models to solve unsteady ow problems has resulted in several semi-empirical models capable of effectively analyzing unsteady aerodynamics in a fraction of the time required by high-order methods. However, due to the various complexities associated with time-dependent flows, several empirical constants and curve fits derived from existing experimental and computational results are required by the semi-empirical models to be an effective analysis tool. The aim of the current work is to develop a low-order model capable of simulating incompressible dynamic-stall type ow problems with a focus on accurately modeling the unsteady ow physics with the aim of reducing empirical dependencies. The lumped-vortex-element (LVE) algorithm is used as the baseline unsteady inviscid model to which augmentations are applied to model unsteady viscous effects. The current research is divided into two phases. The first phase focused on augmentations aimed at modeling pure unsteady trailing-edge boundary-layer separation and stall without leading-edge vortex (LEV) formation. The second phase is targeted at including LEV shedding capabilities to the LVE algorithm and combining with the trailing-edge separation model from phase one to realize a holistic, optimized, and robust low-order dynamic stall model. In phase one, initial augmentations to theory were focused on modeling the effects of steady trailing-edge separation by implementing a non-linear decambering
Visual comparison for information visualization
Gleicher, M.
2011-09-07
Data analysis often involves the comparison of complex objects. With the ever increasing amounts and complexity of data, the demand for systems to help with these comparisons is also growing. Increasingly, information visualization tools support such comparisons explicitly, beyond simply allowing a viewer to examine each object individually. In this paper, we argue that the design of information visualizations of complex objects can, and should, be studied in general, that is independently of what those objects are. As a first step in developing this general understanding of comparison, we propose a general taxonomy of visual designs for comparison that groups designs into three basic categories, which can be combined. To clarify the taxonomy and validate its completeness, we provide a survey of work in information visualization related to comparison. Although we find a great diversity of systems and approaches, we see that all designs are assembled from the building blocks of juxtaposition, superposition and explicit encodings. This initial exploration shows the power of our model, and suggests future challenges in developing a general understanding of comparative visualization and facilitating the development of more comparative visualization tools. © The Author(s) 2011.
Melcher, David
2011-02-27
Our vision remains stable even though the movements of our eyes, head and bodies create a motion pattern on the retina. One of the most important, yet basic, feats of the visual system is to correctly determine whether this retinal motion is owing to real movement in the world or rather our own self-movement. This problem has occupied many great thinkers, such as Descartes and Helmholtz, at least since the time of Alhazen. This theme issue brings together leading researchers from animal neurophysiology, clinical neurology, psychophysics and cognitive neuroscience to summarize the state of the art in the study of visual stability. Recently, there has been significant progress in understanding the limits of visual stability in humans and in identifying many of the brain circuits involved in maintaining a stable percept of the world. Clinical studies and new experimental methods, such as transcranial magnetic stimulation, now make it possible to test the causal role of different brain regions in creating visual stability and also allow us to measure the consequences when the mechanisms of visual stability break down.
Energy Technology Data Exchange (ETDEWEB)
Pinker, S.
1985-01-01
This collection of research papers on visual cognition first appeared as a special issue of Cognition: International Journal of Cognitive Science. The study of visual cognition has seen enormous progress in the past decade, bringing important advances in our understanding of shape perception, visual imagery, and mental maps. Many of these discoveries are the result of converging investigations in different areas, such as cognitive and perceptual psychology, artificial intelligence, and neuropsychology. This volume is intended to highlight a sample of work at the cutting edge of this research area for the benefit of students and researchers in a variety of disciplines. The tutorial introduction that begins the volume is designed to help the nonspecialist reader bridge the gap between the contemporary research reported here and earlier textbook introductions or literature reviews.
DEFF Research Database (Denmark)
Picozzi, Matteo; Verdezoto, Nervo; Pouke, Matti
2013-01-01
techniques to give a rapid overview of trafﬁc data. We illustrate our approach as a case study for trafﬁc visualization systems, using datasets from the city of Oulu that can be extended to other city planning activities. We also report the feedback of real users (trafﬁc management employees, trafﬁc police...
Eliazar, Iddo
2016-07-01
The study of socioeconomic inequality is of substantial importance, scientific and general alike. The graphic visualization of inequality is commonly conveyed by Lorenz curves. While Lorenz curves are a highly effective statistical tool for quantifying the distribution of wealth in human societies, they are less effective a tool for the visual depiction of socioeconomic inequality. This paper introduces an alternative to Lorenz curves-the hill curves. On the one hand, the hill curves are a potent scientific tool: they provide detailed scans of the rich-poor gaps in human societies under consideration, and are capable of accommodating infinitely many degrees of freedom. On the other hand, the hill curves are a powerful infographic tool: they visualize inequality in a most vivid and tangible way, with no quantitative skills that are required in order to grasp the visualization. The application of hill curves extends far beyond socioeconomic inequality. Indeed, the hill curves are highly effective 'hyperspectral' measures of statistical variability that are applicable in the context of size distributions at large. This paper establishes the notion of hill curves, analyzes them, and describes their application in the context of general size distributions.
DEFF Research Database (Denmark)
Pedersen, Pia
2012-01-01
the finished charts as a starting point and then going back to the beginning; furthermore, this inquiry presents a novel approach to clarifying the process by designing symbols and diagrams. It will be demonstrated that transformation offers an improved approach to data visualization. The message in the chart...... is not preformed, but formed through the process of transformation; this means that the purpose of transformation is not the styling of charts with pictograms, but rather creating a meaningful message. The contribution of this paper is an elaborated understanding of the process of transformation...... design. Recently transformation has attracted renewed interest because of the book The Transformer written by Robin Kinross and Marie Neurath. My on-going research project, summarized in this paper, identifies and depicts the essential principles of data visualization underlying the process...
2000-01-01
Reality Capture Technologies, Inc. is a spinoff company from Ames Research Center. Offering e-business solutions for optimizing management, design and production processes, RCT uses visual collaboration environments (VCEs) such as those used to prepare the Mars Pathfinder mission.The product, 4-D Reality Framework, allows multiple users from different locations to manage and share data. The insurance industry is one targeted commercial application for this technology.
Energy Technology Data Exchange (ETDEWEB)
Asuaje, M.
2003-07-15
Faced with the problem of design in the pump industry, the main difficulty of manufacturers is to have fast, reliable and accurate methods. This research work involving, both theory and experiments deals, with this topic. We have developed a complete procedure for design, performance analysis and optimization of centrifugal and mixed incompressible flow turbomachinery. First of all, the definition of the pump geometry as well as the analysis of its global performance are carried out starting from the mean streamline method (1D), based on both ideal models and experimental correlations. A second stage of optimization is achieved from a quasi 3D method, by studying the meridional flow and blade to blade flow, using REMIX software developed by LEMFI. Finally, a three-dimensional flow study is performed by CFD tools from AEA-Technology group (CFX). The three-dimensional study provides the means to complete and validate the established procedure. To illustrate this procedure, a centrifugal machine with a volute was studied used. First, the analysis of the existing impeller was carried out to develop the various steps of the procedure. Then, the whole impeller-volute pump, was studied and compared with the previous trial runs. Special attention was paid to unsteady effects, resulting from impeller volute interaction. The results obtained are satisfactory. Finally, the integral method was applied to optimize a mixed flow pump equipped with a de-swirl. As it is a badly dimensioned pump, it is a good example of what this method can do. (author)
Tversky, Barbara
2011-07-01
Depictive expressions of thought predate written language by thousands of years. They have evolved in communities through a kind of informal user testing that has refined them. Analyzing common visual communications reveals consistencies that illuminate how people think as well as guide design; the process can be brought into the laboratory and accelerated. Like language, visual communications abstract and schematize; unlike language, they use properties of the page (e.g., proximity and place: center, horizontal/up-down, vertical/left-right) and the marks on it (e.g., dots, lines, arrows, boxes, blobs, likenesses, symbols) to convey meanings. The visual expressions of these meanings (e.g., individual, category, order, relation, correspondence, continuum, hierarchy) have analogs in language, gesture, and especially in the patterns that are created when people design the world around them, arranging things into piles and rows and hierarchies and arrays, spatial-abstraction-action interconnections termed spractions. The designed world is a diagram. Copyright © 2010 Cognitive Science Society, Inc.
Energy Technology Data Exchange (ETDEWEB)
Costa, Gustavo Koury
2004-11-15
Although incompressible fluid flows can be regarded as a particular case of a general problem, numerical methods and the mathematical formulation aimed to solve compressible and incompressible flows have their own peculiarities, in such a way, that it is generally not possible to attain both regimes with a single approach. In this work, we start from a typically compressible formulation, slightly modified to make use of pressure variables and, through augmenting the stabilising parameters, we end up with a simplified model which is able to deal with a wide range of flow regimes, from supersonic to low speed gas flows. The resulting methodology is flexible enough to allow for the simulation of liquid flows as well. Examples using conservative and pressure variables are shown and the results are compared to those published in the literature, in order to validate the method. (author)
Développement d'un modèle numérique pour l'écoulement triphasique de fluides incompressibles
Schneider, Lauriane
2015-01-01
Numerical simulation has become a crucial tool in addressing water-resource management and other environmental problems such as polluted sites monitoring. The aim of this work is to model the flow of a dense non aqueous phase liquid (DNAPL) in the subsurface by developing a numerical code to simulate three-phase (DNAPL, water, and gas), incompressible flow in porous media. The mathematical model for multiphase flow in porous media is generally composed of a system of one pressure and two satu...
Directory of Open Access Journals (Sweden)
P. S. B. Zdanski
Full Text Available Abstract The present work deals with numerical simulation of the incompressible turbulent flow of a binary mixture air-water vapor inside channels. Calculations are performed using the RANS (Reynolds Average Navier-Stokes Equations formulation in addition to the standart k-ε turbulence model. The mathematical model is discretized by a finite difference scheme, being adopted second order accurate expressions for both convection and diffusion terms. The mesh arrangement is collocated and artificial dissipation terms are added to control the odd-even decoupling problem. The numerical scheme is applied to solve the flow of a binary mixture of air-water vapor inside plane channels and sudden expansions. The validation performed indicates that the present method reproduces satisfactorily the literature data for both concentration profiles and Sherwood number. Furthermore, the parametric analysis performed indicates that the drying process (wall mass flux is very sensitive to the flow parameters investigated, i.e., inlet flow velocity and channel expansion ratio.
Pitton, Giuseppe; Quaini, Annalisa; Rozza, Gianluigi
2017-09-01
We focus on reducing the computational costs associated with the hydrodynamic stability of solutions of the incompressible Navier-Stokes equations for a Newtonian and viscous fluid in contraction-expansion channels. In particular, we are interested in studying steady bifurcations, occurring when non-unique stable solutions appear as physical and/or geometric control parameters are varied. The formulation of the stability problem requires solving an eigenvalue problem for a partial differential operator. An alternative to this approach is the direct simulation of the flow to characterize the asymptotic behavior of the solution. Both approaches can be extremely expensive in terms of computational time. We propose to apply Reduced Order Modeling (ROM) techniques to reduce the demanding computational costs associated with the detection of a type of steady bifurcations in fluid dynamics. The application that motivated the present study is the onset of asymmetries (i.e., symmetry breaking bifurcation) in blood flow through a regurgitant mitral valve, depending on the Reynolds number and the regurgitant mitral valve orifice shape.
Directory of Open Access Journals (Sweden)
Taymaz Imdat
2015-01-01
Full Text Available The Lattice Boltzmann Method is applied to computationally investigate the laminar flow and heat transfer of an incompressible fluid with constant material properties in a two-dimensional channel with a built-in bluff body. In this study, a triangular prism is taken as the bluff body. Not only the momentum transport, but also the energy transport is modeled by the Lattice Boltzmann Method. A uniform lattice structure with a single time relaxation rule is used. For obtaining a higher flexibility on the computational grid, interpolation methods are applied, where the information is transferred from the lattice structure to the computational grid by Lagrange interpolation. The flow is investigated for different Reynolds numbers, while keeping the Prandtl number at the constant value of 0.7. The results show how the presence of a triangular prism effects the flow and heat transfer patterns for the steady-state and unsteady-periodic flow regimes. As an assessment of the accuracy of the developed Lattice Boltzmann code, the results are compared with those obtained by a commercial Computational Fluid Dynamics code. It is observed that the present Lattice Boltzmann code delivers results that are of similar accuracy to the well-established Computational Fluid Dynamics code, with much smaller computational time for the prediction of the unsteady phenomena.
Rosenfeld, Moshe; Kwak, Dochan; Vinokur, Marcel
1992-01-01
A fractional step method is developed for solving the time-dependent three-dimensional incompressible Navier-Stokes equations in generalized coordinate systems. The primitive variable formulation uses the pressure, defined at the center of the computational cell, and the volume fluxes across the faces of the cells as the dependent variables, instead of the Cartesian components of the velocity. This choice is equivalent to using the contravariant velocity components in a staggered grid multiplied by the volume of the computational cell. The governing equations are discretized by finite volumes using a staggered mesh system. The solution of the continuity equation is decoupled from the momentum equations by a fractional step method which enforces mass conservation by solving a Poisson equation. This procedure, combined with the consistent approximations of the geometric quantities, is done to satisfy the discretized mass conservation equation to machine accuracy, as well as to gain the favorable convergence properties of the Poisson solver. The momentum equations are solved by an approximate factorization method, and a novel ZEBRA scheme with four-color ordering is devised for the efficient solution of the Poisson equation. Several two- and three-dimensional laminar test cases are computed and compared with other numerical and experimental results to validate the solution method. Good agreement is obtained in all cases.
Directory of Open Access Journals (Sweden)
Vincent Olunloyo
2016-12-01
Full Text Available In this paper, we present an analytical method for solving a well-posed boundary value problem of mathematical physics governing the vibration characteristics of an internal flow propelled fluid-structure interaction where the pipeline segment is idealized as an elastic hollow beam conveying an incompressible fluid on a viscoelastic foundation. The effect of Coriolis and damping forces on the overall dynamic response of the system is investigated. In actuality, for a pipe segment supported at both ends and subject to a free motion, these two forces generate conjugate complex frequencies for all flow velocities. On employing integral transforms and complex variable functions, a closed form analytical expression is derived for the overall dynamic response. It is demonstrated that a concise mathematical expression for the natural frequency associated with any mode of vibration can be deduced from the algebraic product of the complex frequency pairs. By a way of comparative analysis for damping decrement physics reminiscent with laminated structures, mathematical expressions are derived to illustrate viscoelastic damping effects on dynamic stability for any flow velocity. The integrity of the analytical solution is verified and validated by confirming theresults in literature in appropriate asymptotic limits.
Energy Technology Data Exchange (ETDEWEB)
Shadid, John Nicolas (Sandia National Laboratories, Albuquerque, NM); Elman, Howard (University of Maryland, College Park, MD); Shuttleworth, Robert R. (University of Maryland, College Park, MD); Howle, Victoria E.; Tuminaro, Raymond Stephen
2007-04-01
In recent years, considerable effort has been placed on developing efficient and robust solution algorithms for the incompressible Navier-Stokes equations based on preconditioned Krylov methods. These include physics-based methods, such as SIMPLE, and purely algebraic preconditioners based on the approximation of the Schur complement. All these techniques can be represented as approximate block factorization (ABF) type preconditioners. The goal is to decompose the application of the preconditioner into simplified sub-systems in which scalable multi-level type solvers can be applied. In this paper we develop a taxonomy of these ideas based on an adaptation of a generalized approximate factorization of the Navier-Stokes system first presented in [25]. This taxonomy illuminates the similarities and differences among these preconditioners and the central role played by efficient approximation of certain Schur complement operators. We then present a parallel computational study that examines the performance of these methods and compares them to an additive Schwarz domain decomposition (DD) algorithm. Results are presented for two and three-dimensional steady state problems for enclosed domains and inflow/outflow systems on both structured and unstructured meshes. The numerical experiments are performed using MPSalsa, a stabilized finite element code.
Uma, B; Radhakrishnan, R; Eckmann, D M; Ayyaswamy, P S
2013-01-01
A hybrid scheme based on Markovian fluctuating hydrodynamics of the fluid and a non-Markovian Langevin dynamics with the Ornstein-Uhlenbeck noise perturbing the translational and rotational equations of motion of a nanoparticle is employed to study the thermal motion of a nearly neutrally buoyant nanoparticle in an incompressible Newtonian fluid medium. A direct numerical simulation adopting an arbitrary Lagrangian-Eulerian based finite element method is employed in simulating the thermal motion of the particle suspended in the fluid contained in a cylindrical vessel. The instantaneous flow around the particle and the particle motion are fully resolved. The numerical results show that (a) the calculated temperature of the nearly neutrally buoyant Brownian particle in a quiescent fluid satisfies the equipartition theorem; (b) the translational and rotational decay of the velocity autocorrelation functions result in algebraic tails, over long time; (c) the translational and rotational mean square displacements of the particle obeys Stokes-Einstein and Stokes-Einstein-Debye relations, respectively; and (d) the parallel and perpendicular diffusivities of the particle closer to the wall are consistent with the analytical results, where available. The study has important implications for designing nanocarriers for targeted drug delivery.
Nouri-Borujerdi, Ali; Moazezi, Arash
2018-01-01
The current study investigates the conjugate heat transfer characteristics for laminar flow in backward facing step channel. All of the channel walls are insulated except the lower thick wall under a constant temperature. The upper wall includes a insulated obstacle perpendicular to flow direction. The effect of obstacle height and location on the fluid flow and heat transfer are numerically explored for the Reynolds number in the range of 10 ≤ Re ≤ 300. Incompressible Navier-Stokes and thermal energy equations are solved simultaneously in fluid region by the upwind compact finite difference scheme based on flux-difference splitting in conjunction with artificial compressibility method. In the thick wall, the energy equation is obtained by Laplace equation. A multi-block approach is used to perform parallel computing to reduce the CPU time. Each block is modeled separately by sharing boundary conditions with neighbors. The developed program for modeling was written in FORTRAN language with OpenMP API. The obtained results showed that using of the multi-block parallel computing method is a simple robust scheme with high performance and high-order accurate. Moreover, the obtained results demonstrated that the increment of Reynolds number and obstacle height as well as decrement of horizontal distance between the obstacle and the step improve the heat transfer.
Ha, Sanghyun; Park, Junshin; You, Donghyun
2017-11-01
Utility of the computational power of modern Graphics Processing Units (GPUs) is elaborated for solutions of incompressible Navier-Stokes equations which are integrated using a semi-implicit fractional-step method. Due to its serial and bandwidth-bound nature, the present choice of numerical methods is considered to be a good candidate for evaluating the potential of GPUs for solving Navier-Stokes equations using non-explicit time integration. An efficient algorithm is presented for GPU acceleration of the Alternating Direction Implicit (ADI) and the Fourier-transform-based direct solution method used in the semi-implicit fractional-step method. OpenMP is employed for concurrent collection of turbulence statistics on a CPU while Navier-Stokes equations are computed on a GPU. Extension to multiple NVIDIA GPUs is implemented using NVLink supported by the Pascal architecture. Performance of the present method is experimented on multiple Tesla P100 GPUs compared with a single-core Xeon E5-2650 v4 CPU in simulations of boundary-layer flow over a flat plate. Supported by the National Research Foundation of Korea (NRF) Grant funded by the Korea government (Ministry of Science, ICT and Future Planning NRF-2016R1E1A2A01939553, NRF-2014R1A2A1A11049599, and Ministry of Trade, Industry and Energy 201611101000230).
National Research Council Canada - National Science Library
Cavanagh, Patrick
2011-01-01
... is unified in our mind even if not in the image. The construction of these entities is the task of visual cognition and, in almost all cases, each construct is a choice among an infinity of possibilities, chosen based on likelihood, bias, or a whim, but chosen by rejecting other valid competitors. The entities are not limited to static surfaces or structures but also include dynamic structures that only emerge over time – from dots that appear to be walking like a human or a moon orbiting a planet, to the...
How information visualization novices construct visualizations.
Grammel, Lars; Tory, Melanie; Storey, Margaret-Anne
2010-01-01
It remains challenging for information visualization novices to rapidly construct visualizations during exploratory data analysis. We conducted an exploratory laboratory study in which information visualization novices explored fictitious sales data by communicating visualization specifications to a human mediator, who rapidly constructed the visualizations using commercial visualization software. We found that three activities were central to the iterative visualization construction process: data attribute selection, visual template selection, and visual mapping specification. The major barriers faced by the participants were translating questions into data attributes, designing visual mappings, and interpreting the visualizations. Partial specification was common, and the participants used simple heuristics and preferred visualizations they were already familiar with, such as bar, line and pie charts. We derived abstract models from our observations that describe barriers in the data exploration process and uncovered how information visualization novices think about visualization specifications. Our findings support the need for tools that suggest potential visualizations and support iterative refinement, that provide explanations and help with learning, and that are tightly integrated into tool support for the overall visual analytics process.
Visual analytics in scalable visualization environments
Yamaoka, So
2011-01-01
Visual analytics is an interdisciplinary field that facilitates the analysis of the large volume of data through interactive visual interface. This dissertation focuses on the development of visual analytics techniques in scalable visualization environments. These scalable visualization environments offer a high-resolution, integrated virtual space, as well as a wide-open physical space that affords collaborative user interaction. At the same time, the sheer scale of these environments poses ...
Visualization rhetoric: framing effects in narrative visualization.
Hullman, Jessica; Diakopoulos, Nicholas
2011-12-01
Narrative visualizations combine conventions of communicative and exploratory information visualization to convey an intended story. We demonstrate visualization rhetoric as an analytical framework for understanding how design techniques that prioritize particular interpretations in visualizations that "tell a story" can significantly affect end-user interpretation. We draw a parallel between narrative visualization interpretation and evidence from framing studies in political messaging, decision-making, and literary studies. Devices for understanding the rhetorical nature of narrative information visualizations are presented, informed by the rigorous application of concepts from critical theory, semiotics, journalism, and political theory. We draw attention to how design tactics represent additions or omissions of information at various levels-the data, visual representation, textual annotations, and interactivity-and how visualizations denote and connote phenomena with reference to unstated viewing conventions and codes. Classes of rhetorical techniques identified via a systematic analysis of recent narrative visualizations are presented, and characterized according to their rhetorical contribution to the visualization. We describe how designers and researchers can benefit from the potentially positive aspects of visualization rhetoric in designing engaging, layered narrative visualizations and how our framework can shed light on how a visualization design prioritizes specific interpretations. We identify areas where future inquiry into visualization rhetoric can improve understanding of visualization interpretation. © 2011 IEEE
Zou, Yongtao; Wang, Xuebing; Chen, Ting; Li, Xuefei; Qi, Xintong; Welch, David; Zhu, Pinwen; Liu, Bingbing; Cui, Tian; Li, Baosheng
2015-01-01
Exploring the structural stability and elasticity of hexagonal ε-NbN helps discover correlations among its physical properties for scientific and technological applications. Here, for the first time, we measured the ultra-incompressibility and high shear rigidity of polycrystalline hexagonal ε-NbN using ultrasonic interferometry and in situ X-ray diffraction, complemented with first-principles density-functional theory calculations up to 30 GPa in pressure. Using a finite strain equation of state approach, the elastic bulk and shear moduli, as well as their pressure dependences are derived from the measured velocities and densities, yielding BS0 = 373.3(15) GPa, G0 = 200.5(8) GPa, ∂BS/∂P = 3.81(3) and ∂G/∂P = 1.67(1). The hexagonal ε-NbN possesses a very high bulk modulus, rivaling that of superhard material cBN (B0 = 381.1 GPa). The high shear rigidity is comparable to that for superhard γ-B (G0 = 227.2 GPa). We found that the crystal structure of transition-metal nitrides and the outmost electrons of the corresponding metals may dominate their pressure dependences in bulk and shear moduli. In addition, the elastic moduli, Vickers hardness, Debye temperature, melting temperature and a possible superconductivity of hexagonal ε-NbN all increase with pressures, suggesting its exceptional suitability for applications under extreme conditions. PMID:26028439
Kiris, Cetin C.; Kwak, Dochan; Rogers, Stuart E.
2002-01-01
This paper reviews recent progress made in incompressible Navier-Stokes simulation procedures and their application to problems of engineering interest. Discussions are focused on the methods designed for complex geometry applications in three dimensions, and thus are limited to primitive variable formulation. A summary of efforts in flow solver development is given followed by numerical studies of a few example problems of current interest. Both steady and unsteady solution algorithms and their salient features are discussed. Solvers discussed here are based on a structured-grid approach using either a finite -difference or a finite-volume frame work. As a grand-challenge application of these solvers, an unsteady turbopump flow simulation procedure has been developed which utilizes high performance computing platforms. In the paper, the progress toward the complete simulation capability of the turbo-pump for a liquid rocket engine is reported. The Space Shuttle Main Engine (SSME) turbo-pump is used as a test case for evaluation of two parallel computing algorithms that have been implemented in the INS3D code. The relative motion of the grid systems for the rotorstator interaction was obtained using overact grid techniques. Unsteady computations for the SSME turbo-pump, which contains 114 zones with 34.5 million grid points, are carried out on SCSI Origin 3000 systems at NASA Ames Research Center. The same procedure has been extended to the development of NASA-DeBakey Ventricular Assist Device (VAD) that is based on an axial blood pump. Computational, and clinical analysis of this device are presented.
Lechner, Joseph H.
1999-10-01
This report describes two classroom activities that help students visualize the abstract concept of entropy and apply the second law of thermodynamics to real situations. (i) A sealed "rainbow tube" contains six smaller vessels, each filled with a different brightly colored solution (low entropy). When the tube is inverted, the solutions mix together and react to form an amorphous precipitate (high entropy). The change from low entropy to high entropy is irreversible as long as the tube remains sealed. (ii) When U.S. currency is withdrawn from circulation, intact bills (low entropy) are shredded into small fragments (high entropy). Shredding is quick and easy; the reverse process is clearly nonspontaneous. It is theoretically possible, but it is time-consuming and energy-intensive, to reassemble one bill from a pile that contains fragments of hundreds of bills. We calculate the probability P of drawing pieces of only one specific bill from a mixture containing one pound of bills, each shredded into n fragments. This result can be related to Boltzmann's entropy formula S?=klnW.
Tetervin, Neal; Lin, Chia Chiao
1951-01-01
A general integral form of the boundary-layer equation, valid for either laminar or turbulent incompressible boundary-layer flow, is derived. By using the experimental finding that all velocity profiles of the turbulent boundary layer form essentially a single-parameter family, the general equation is changed to an equation for the space rate of change of the velocity-profile shape parameter. The lack of precise knowledge concerning the surface shear and the distribution of the shearing stress across turbulent boundary layers prevented the attainment of a reliable method for calculating the behavior of turbulent boundary layers.
CSIR Research Space (South Africa)
Schoombie, Janine
2017-10-01
Full Text Available Fluent and STAR-CCM+ simulations for a tangent ogive slender body with a structured mesh at incompressible flow conditions Janine Schoombie CSIR Background • First round of simulations in 2013 in ANSYS Fluent v15.0 • Validated experimentally • Three... – 0° ≤ α ≤ 25° • Solutions converged after ≈ 10 000 iterations STAR-CCM+ Simulated Geometry • Configuration s/D=1.25 successfully simulated to convergence Velocity Inlet Pressure Outlet Symmetry plane Body geometry Import Fluent case files into STAR...
Li, T; Liu, Y; Marks, R; Nayak, B K; Rao, P V Madhusudhana; Fujiwara, M; Hashimoto, H; Kawase, K; Nakanishi, K; Okumura, S; Yosoi, M; Itoh, M; Ichikawa, M; Matsuo, R; Terazano, T; Uchida, M; Kawabata, T; Akimune, H; Iwao, Y; Murakami, T; Sakaguchi, H; Terashima, S; Yasuda, Y; Zenihiro, J; Harakeh, M N
2007-01-01
The strength distributions of the giant monopole resonance (GMR) have been measured in the even-A Sn isotopes (A=112--124) with inelastic scattering of 400-MeV $\\alpha$ particles in the angular range $0^\\circ$--$8.5^\\circ$. We find that the experimentally-observed GMR energies of the Sn isotopes are lower than the values predicted by theoretical calculations that reproduce the GMR energies in $^{208}$Pb and $^{90}$Zr very well. From the GMR data, a value of $K_{\\tau} = -550 \\pm 100$ MeV is obtained for the asymmetry-term in the nuclear incompressibility.
Godoy, Mario
1991-01-01
Se investiga el flujo incompressible en régimen de materiales con características friccionales y cohesivas, empleando métodos numéricos. Se supone un flujo viscoplástico, para el cual se desarrolla una nueva expresión para el coeficiente de viscosidad . La discretización del modelo se lleva a cabo por medio de una formulación de Elementos Finitos en términos de velocidades, en la cual se satisface incompressibilidad usando una función de penalización. La formulación ha sido implementada para ...
... Frequently Asked Questions Español Condiciones Chinese Conditions Cortical Visual Impairment En Español Read in Chinese What is cortical visual impairment? Cortical visual impairment (CVI) is a decreased ...
Maes, Alfons
2017-04-01
Climate change is a playground for visualization. Yet research and technological innovations in visual communication and data visualization do not account for a substantial part of the world's population: vulnerable audiences with low levels of literacy.
Ihmsen, Markus; Cornelis, Jens; Solenthaler, Barbara; Horvath, Christopher; Teschner, Matthias
2014-03-01
We propose a novel formulation of the projection method for Smoothed Particle Hydrodynamics (SPH). We combine a symmetric SPH pressure force and an SPH discretization of the continuity equation to obtain a discretized form of the pressure Poisson equation (PPE). In contrast to previous projection schemes, our system does consider the actual computation of the pressure force. This incorporation improves the convergence rate of the solver. Furthermore, we propose to compute the density deviation based on velocities instead of positions as this formulation improves the robustness of the time-integration scheme. We show that our novel formulation outperforms previous projection schemes and state-of-the-art SPH methods. Large time steps and small density deviations of down to 0.01 percent can be handled in typical scenarios. The practical relevance of the approach is illustrated by scenarios with up to 40 million SPH particles.
Directory of Open Access Journals (Sweden)
M.M. Bhatti
2017-06-01
Full Text Available Biologically-inspired propulsion systems are currently receiving significant interest in the aerospace sector. Since many spacecraft propulsion systems operate at high temperatures, thermal radiation is important as a mode of heat transfer. Motivated by these developments, in the present article, the influence of nonlinear thermal radiation (via the Rosseland diffusion flux model has been studied on the laminar, incompressible, dissipative EMHD (Electro-magneto-hydrodynamic peristaltic propulsive flow of a non-Newtonian (Jefferys viscoelastic dusty fluid containing solid particles through a porous planar channel. The fluid is electrically-conducting and a constant static magnetic field is applied transverse to the flow direction (channel walls. Slip effects are also included. Magnetic induction effects are neglected. The mathematical formulation is based on continuity, momentum and energy equations with appropriate boundary conditions, which are simplified by neglecting the inertial forces and taking the long wavelength and lubrication approximations. The boundary value problem is then rendered non-dimensional with appropriate variables and the resulting system of reduced ordinary differential equations is solved analytically. The impact of various emerging parameters dictating the non-Newtonian propulsive flow i.e. Prandtl number, radiation parameter, Hartmann number, permeability parameter, Eckert number, particle volume fraction, electric field and slip parameter are depicted graphically. Increasing particle volume fraction is observed to suppress temperature magnitudes. Furthermore the computations demonstrate that an increase in particle volume fraction reduces the pumping rate in retrograde pumping region whereas it causes the opposite effect in the co-pumping region. The trapping mechanism is also visualized with the aid of streamline contour plots. Increasing thermal radiation elevates temperatures. Increasing Hartmann (magnetic body
Gong, Yuezheng; Zhao, Jia; Wang, Qi
2017-10-01
A quasi-incompressible hydrodynamic phase field model for flows of fluid mixtures of two incompressible viscous fluids of distinct densities and viscosities is derived by using the generalized Onsager principle, which warrants the variational structure, the mass conservation and energy dissipation law. We recast the model in an equivalent form and discretize the equivalent system in space firstly to arrive at a time-dependent ordinary differential and algebraic equation (DAE) system, which preserves the mass conservation and energy dissipation law at the semi-discrete level. Then, we develop a temporal discretization scheme for the DAE system, where the mass conservation and the energy dissipation law are once again preserved at the fully discretized level. We prove that the fully discretized algorithm is unconditionally energy stable. Several numerical examples, including drop dynamics of viscous fluid drops immersed in another viscous fluid matrix and mixing dynamics of binary polymeric solutions, are presented to show the convergence property as well as the accuracy and efficiency of the new scheme.
Guo, Z.; Lin, P.; Lowengrub, J.; Wise, S. M.
2017-11-01
In this paper we describe two fully mass conservative, energy stable, finite difference methods on a staggered grid for the quasi-incompressible Navier-Stokes-Cahn-Hilliard (q-NSCH) system governing a binary incompressible fluid flow with variable density and viscosity. Both methods, namely the primitive method (finite difference method in the primitive variable formulation) and the projection method (finite difference method in a projection-type formulation), are so designed that the mass of the binary fluid is preserved, and the energy of the system equations is always non-increasing in time at the fully discrete level. We also present an efficient, practical nonlinear multigrid method - comprised of a standard FAS method for the Cahn-Hilliard equation, and a method based on the Vanka-type smoothing strategy for the Navier-Stokes equation - for solving these equations. We test the scheme in the context of Capillary Waves, rising droplets and Rayleigh-Taylor instability. Quantitative comparisons are made with existing analytical solutions or previous numerical results that validate the accuracy of our numerical schemes. Moreover, in all cases, mass of the single component and the binary fluid was conserved up to 10 to -8 and energy decreases in time.
Koželj, Urša
2013-01-01
In this thesis we discuss cortical visual impairment, diagnosis that is in the developed world in first place, since 20 percent of children with blindness or low vision are diagnosed with it. The objectives of the thesis are to define cortical visual impairment and the definition of characters suggestive of the cortical visual impairment as well as to search for causes that affect the growing diagnosis of cortical visual impairment. There are a lot of signs of cortical visual impairment. ...
Custom Visualization without Real Programming
DEFF Research Database (Denmark)
Pantazos, Kostas
Information Visualization tools have simplified visualization development. Some tools help simple users construct standard visualizations; others help programmers develop custom visualizations. This thesis contributes to the field of Information Visualization and End-User Development. The first c...
Declarative Visualization Queries
Pinheiro da Silva, P.; Del Rio, N.; Leptoukh, G. G.
2011-12-01
In an ideal interaction with machines, scientists may prefer to write declarative queries saying "what" they want from a machine than to write code stating "how" the machine is going to address the user request. For example, in relational database, users have long relied on specifying queries using Structured Query Language (SQL), a declarative language to request data results from a database management system. In the context of visualizations, we see that users are still writing code based on complex visualization toolkit APIs. With the goal of improving the scientists' experience of using visualization technology, we have applied this query-answering pattern to a visualization setting, where scientists specify what visualizations they want generated using a declarative SQL-like notation. A knowledge enhanced management system ingests the query and knows the following: (1) know how to translate the query into visualization pipelines; and (2) how to execute the visualization pipelines to generate the requested visualization. We define visualization queries as declarative requests for visualizations specified in an SQL like language. Visualization queries specify what category of visualization to generate (e.g., volumes, contours, surfaces) as well as associated display attributes (e.g., color and opacity), without any regards for implementation, thus allowing scientists to remain partially unaware of a wide range of visualization toolkit (e.g., Generic Mapping Tools and Visualization Toolkit) specific implementation details. Implementation details are only a concern for our knowledge-based visualization management system, which uses both the information specified in the query and knowledge about visualization toolkit functions to construct visualization pipelines. Knowledge about the use of visualization toolkits includes what data formats the toolkit operates on, what formats they output, and what views they can generate. Visualization knowledge, which is not
Visualization analysis and design
Munzner, Tamara
2015-01-01
Visualization Analysis and Design provides a systematic, comprehensive framework for thinking about visualization in terms of principles and design choices. The book features a unified approach encompassing information visualization techniques for abstract data, scientific visualization techniques for spatial data, and visual analytics techniques for interweaving data transformation and analysis with interactive visual exploration. It emphasizes the careful validation of effectiveness and the consideration of function before form. The book breaks down visualization design according to three questions: what data users need to see, why users need to carry out their tasks, and how the visual representations proposed can be constructed and manipulated. It walks readers through the use of space and color to visually encode data in a view, the trade-offs between changing a single view and using multiple linked views, and the ways to reduce the amount of data shown in each view. The book concludes with six case stu...
The Visual Analysis of Visual Metaphor.
Dake, Dennis M.; Roberts, Brian
This paper presents an approach to understanding visual metaphor which uses metaphoric analysis and comprehension by graphic and pictorial means. The perceptible qualities of shape, line, form, color, and texture, that make up the visual structure characteristic of any particular shape, configuration, or scene, are called physiognomic properties;…
Tominski, Christian
2015-01-01
Visualization has become a valuable means for data exploration and analysis. Interactive visualization combines expressive graphical representations and effective user interaction. Although interaction is an important component of visualization approaches, much of the visualization literature tends to pay more attention to the graphical representation than to interaction.The goal of this work is to strengthen the interaction side of visualization. Based on a brief review of general aspects of interaction, we develop an interaction-oriented view on visualization. This view comprises five key as
DEFF Research Database (Denmark)
Habekost, Thomas; Starrfelt, Randi
2009-01-01
Psychophysical studies have identified two distinct limitations of visual attention capacity: processing speed and apprehension span. Using a simple test, these cognitive factors can be analyzed by Bundesen's Theory of Visual Attention (TVA). The method has strong specificity and sensitivity...... to patient testing, and review existing TVA-based patient studies organized by lesion anatomy. Lesions in three anatomical regions affect visual capacity: The parietal lobes, frontal cortex and basal ganglia, and extrastriate cortex. Visual capacity thus depends on large, bilaterally distributed anatomical...... networks that include several regions outside the visual system. The two visual capacity parameters are functionally separable, but seem to rely on largely overlapping brain areas....
Araki, Keisuke
2016-01-01
In this study, the dynamics of a dissipationless incompressible Hall magnetohydrodynamic (HMHD) medium are formulated as geodesics on a direct product of two volume-preserving diffeomorphism groups. Examinations of the stabilities of the hydrodynamic (HD, $\\alpha=0$) and magnetohydrodynamic (MHD, $\\alpha\\to0$) motions and the $O(\\alpha)$ Hall-term effect in terms of the Jacobi equation and the Riemannian sectional curvature tensor are presented, where {\\alpha} represents the Hall-term strength parameter. Formulations are given for the geodesic and Jacobi equations based on a linear connection with physically desirable properties, which agrees with the Levi-Civita connection. Derivations of the explicit normal-mode expressions for the Riemannian metric, Levi-Civita connection, and related formulae and equations are also provided using the generalized Els\\"asser variables (GEVs). It is very interesting that the sectional curvatures of the MHD and HMHD systems between two GEV modes were found to take both the po...
Dharodi, Vikram; Patel, Bhavesh; Kaw, Predhiman
2015-01-01
The strongly coupled dusty plasma has often been modelled by the Generalized Hydrodynamic (GHD) model used for representing visco-elastic fluid systems. The incompressible limit of the model which supports transverse shear wave mode is studied in detail. In particular dipole structures are observed to emit transverse shear waves in both the limits of sub and super - luminar propagation, where the structures move slower and faster than the phase velocity of the shear waves, respectively. In the sub - luminar limit the dipole gets engulfed within the shear waves emitted by itself, which then backreacts on it and ultimately the identity of the structure is lost. However, in the super - luminar limit the emission appears like a wake from the tail region of the dipole. The dipole, however, keeps propagating forward with little damping but minimal distortion in its form. A Poynting like conservation law with radiative, convective and dissipative terms being responsible for the evolution of W , which is similar to `...
Bruno Galelli Chieregatti
2012-01-01
O presente trabalho é o início de um estudo da aplicação do método de otimização conhecido como adjunto em escoamentos incompressíveis, viscosos e periódicos, envolvendo um problema de bastante interesse: a análise da aplicação de splitter plates em cilindros de seção circular. Conhecido por sua simplicidade, o splitter plate, que consiste em uma placa plana alinhada ao escoamento e colocada a jusante do corpo, é um dispositivo efetivo na mudança de comportamento da esteira de vórtices de Von...
Energy Technology Data Exchange (ETDEWEB)
Patel, D. [Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States); Garg, U., E-mail: garg@nd.edu [Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States); Fujiwara, M. [Research Center for Nuclear Physics, Osaka University, Osaka 567-0047 (Japan); Akimune, H. [Department of Physics, Konan University, Kobe 568-8501 (Japan); Berg, G.P.A. [Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States); Harakeh, M.N. [Kernfysisch Versneller Instituut, University of Groningen, 9747 AA Groningen (Netherlands); Itoh, M. [Cyclotron and Radioisotope Center, Tohoku University, Sendai 980-8578 (Japan); Kawabata, T. [Center for Nuclear Studies, University of Tokyo, Tokyo 113-0033 (Japan); Kawase, K. [Institute of Scientific and Industrial Research, Osaka University, Osaka 567-0047 (Japan); Nayak, B.K. [Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States); Ohta, T. [Research Center for Nuclear Physics, Osaka University, Osaka 567-0047 (Japan); Ouchi, H. [Cyclotron and Radioisotope Center, Tohoku University, Sendai 980-8578 (Japan); Piekarewicz, J. [Department of Physics, Florida State University, Tallahassee, FL 32306 (United States); Uchida, M. [Department of Physics, Tokyo Institute of Technology, Tokyo 152-8850 (Japan); Yoshida, H.P. [Cyclotron and Radioisotope Center, Tohoku University, Sendai 980-8578 (Japan); Yosoi, M. [Research Center for Nuclear Physics, Osaka University, Osaka 567-0047 (Japan)
2012-12-05
The isoscalar giant monopole resonance (ISGMR) in even-A Cd isotopes has been studied by inelastic {alpha}-scattering at 100 MeV/u and at extremely forward angles, including 0 Degree-Sign . The asymmetry term in the nuclear incompressibility extracted from the ISGMR in Cd isotopes is found to be K{sub {tau}}=-555{+-}75 MeV, confirming the value previously obtained from the Sn isotopes. ISGMR strength has been computed in relativistic RPA using NL3 and FSUGold effective interactions. Both models significantly overestimate the centroids of the ISGMR strength in the Cd isotopes. Combined with other recent theoretical effort, the question of the 'softness' of the open-shell nuclei in the tin region remains open still.
Abdelmassih, G.; Vernet, A.; Pallares, J.
2012-11-01
A three-dimensional numerical simulation study for both laminar steady and unsteady regimes has been carried out for the mixed convective flow over a three-dimensional cubical open cavity. The cavity is heated from below at constant temperature while the other walls are adiabatic. The numerical simulation has been done using a three-dimensional incompressible finite volume flow solver. The effects over the velocity and temperature distribution of the buoyancy forces acting perpendicular to the mainstream flow are studied for Reynolds numbers (Re) between 100 and 1500; Prandtl number (Pr) is set to 0.7 and Richardson number (Ri) between 10-3 to 101. The phenomenological description of the mixed convection inside and outside the cavity and the combined effects of the natural and forced convection have been obtained. For both high Re and Ri the flow becomes unsteady. The mixed convection effects dominate the flow transport mechanism and push the recirculation zone and the flow further upstream.
Directory of Open Access Journals (Sweden)
Natal'ya V. Burmasheva
2017-05-01
Full Text Available The exact solution of the definition of convective motions in a layered large-scale flows of a viscous incompressible fluid in a steady case is considered. It was shown that the received problem is, firstly, overdetermined and, secondly, a nonlinear (due to the presence of members of a convective derivative in a heat conduction equation. Also it was shown that the solution class choice can eliminate the override, and the specification of a boundary conditions can reduce the problem to the study of a thermal capillary convection (convection Benard–Marangoni. Then conditions of the counterflow appearance are defined, and their possible amount is investigated. In addition, the analysis of the nonvortex region in the test flow is made. And it was shown that under certain combinations of system parameters the vortex can change the direction.
Energy Technology Data Exchange (ETDEWEB)
Zhou, Yijie [ORNL; Lim, Hyun-Kyung [ORNL; de Almeida, Valmor F [ORNL; Navamita, Ray [State University of New York, Stony Brook; Wang, Shuqiang [State University of New York, Stony Brook; Glimm, James G [ORNL; Li, Xiao-lin [State University of New York, Stony Brook; Jiao, Xiangmin [ORNL
2012-06-01
This progress report describes the development of a front tracking method for the solution of the governing equations of motion for two-phase micromixing of incompressible, viscous, liquid-liquid solvent extraction processes. The ability to compute the detailed local interfacial structure of the mixture allows characterization of the statistical properties of the two-phase mixture in terms of droplets, filaments, and other structures which emerge as a dispersed phase embedded into a continuous phase. Such a statistical picture provides the information needed for building a consistent coarsened model applicable to the entire mixing device. Coarsening is an undertaking for a future mathematical development and is outside the scope of the present work. We present here a method for accurate simulation of the micromixing dynamics of an aqueous and an organic phase exposed to intense centrifugal force and shearing stress. The onset of mixing is the result of the combination of the classical Rayleigh- Taylor and Kelvin-Helmholtz instabilities. A mixing environment that emulates a sector of the annular mixing zone of a centrifugal contactor is used for the mathematical domain. The domain is small enough to allow for resolution of the individual interfacial structures and large enough to allow for an analysis of their statistical distribution of sizes and shapes. A set of accurate algorithms for this application requires an advanced front tracking approach constrained by the incompressibility condition. This research is aimed at designing and implementing these algorithms. We demonstrate verification and convergence results for one-phase and unmixed, two-phase flows. In addition we report on preliminary results for mixed, two-phase flow for realistic operating flow parameters.
Uma, B; Eckmann, D M; Ayyaswamy, P S; Radhakrishnan, R
2012-01-01
A novel hybrid scheme based on Markovian fluctuating hydrodynamics of the fluid and a non-Markovian Langevin dynamics with the Ornstein-Uhlenbeck noise perturbing the translational and rotational equations of motion of the nanoparticle is employed to study the thermal motion of a nanoparticle in an incompressible Newtonian fluid medium. A direct numerical simulation adopting an arbitrary Lagrangian-Eulerian (ALE) based finite element method (FEM) is employed in simulating the thermal motion of a particle suspended in the fluid confined in a cylindrical vessel. The results for thermal equilibrium between the particle and the fluid are validated by comparing the numerically predicted temperature of the nanoparticle with that obtained from the equipartition theorem. The nature of the hydrodynamic interactions is verified by comparing the velocity autocorrelation function (VACF) and mean squared displacement (MSD) with well-known analytical results. For nanoparticle motion in an incompressible fluid, the fluctuating hydrodynamics approach resolves the hydrodynamics correctly but does not impose the correct equipartition of energy based on the nanoparticle mass because of the added mass of the displaced fluid. In contrast, the Langevin approach with an appropriate memory is able to show the correct equipartition of energy, but not the correct short- and long-time hydrodynamic correlations. Using our hybrid approach presented here, we show for the first time, that we can simultaneously satisfy the equipartition theorem and the (short- and long-time) hydrodynamic correlations. In effect, this results in a thermostat that also simultaneously preserves the true hydrodynamic correlations. The significance of this result is that our new algorithm provides a robust computational approach to explore nanoparticle motion in arbitrary geometries and flow fields, while simultaneously enabling us to study carrier adhesion mediated by biological reactions (receptor
Topological Methods for Visualization
Energy Technology Data Exchange (ETDEWEB)
Berres, Anne Sabine [Los Alamos National Lab. (LANL), Los Alamos, NM (United Stat
2016-04-07
This slide presentation describes basic topological concepts, including topological spaces, homeomorphisms, homotopy, betti numbers. Scalar field topology explores finding topological features and scalar field visualization, and vector field topology explores finding topological features and vector field visualization.
Full Text Available ... and other programs with respect to blinding eye diseases, visual disorders, mechanisms of visual function, preservation of sight, and ... National Eye Health Education Program (NEHEP) Diabetic Eye Disease Education Program Glaucoma Education Program Low Vision Education ...
Full Text Available ... and other programs with respect to blinding eye diseases, visual disorders, mechanisms of visual function, preservation of ... National Eye Health Education Program (NEHEP) Diabetic Eye Disease Education Program Glaucoma Education Program Low Vision Education ...
Full Text Available ... programs with respect to blinding eye diseases, visual disorders, mechanisms of visual function, preservation of sight, and the special health problems ... Pressroom Contacts Dustin Hays - Chief, Science Communication dustin.hays@nih.gov Anna Harper - Media Relations ...
Constructing visual representations
DEFF Research Database (Denmark)
Huron, Samuel; Jansen, Yvonne; Carpendale, Sheelagh
2014-01-01
The accessibility of infovis authoring tools to a wide audience has been identified as a major research challenge. A key task in the authoring process is the development of visual mappings. While the infovis community has long been deeply interested in finding effective visual mappings......, comparatively little attention has been placed on how people construct visual mappings. In this paper, we present the results of a study designed to shed light on how people transform data into visual representations. We asked people to create, update and explain their own information visualizations using only...... tangible building blocks. We learned that all participants, most of whom had little experience in visualization authoring, were readily able to create and talk about their own visualizations. Based on our observations, we discuss participants’ actions during the development of their visual representations...
Full Text Available ... to blinding eye diseases, visual disorders, mechanisms of visual function, preservation of sight, and the special health problems and requirements of ... Pressroom Contacts Dustin Hays - Chief, Science Communication dustin.hays@nih.gov Anna Harper - Media Relations ...
Visual Impairment, Including Blindness
... Who Knows What? (log-in required) Select Page Visual Impairment, Including Blindness Mar 31, 2017 Links updated, ... doesn’t wear his glasses. Back to top Visual Impairments in Children Vision is one of our ...
... this page: //medlineplus.gov/ency/article/003396.htm Visual acuity test To use the sharing features on this page, please enable JavaScript. The visual acuity test is used to determine the smallest ...
Full Text Available ... to blinding eye diseases, visual disorders, mechanisms of visual function, preservation of sight, and the special health problems and requirements of the blind.” ... Health Information Frequently asked questions ...
Full Text Available ... USAJobs Home > NEI for Kids > The Visual System All About Vision About the Eye Ask a Scientist ... Tricks Links to More Information Optical Illusions Printables The Visual System Ever wonder how your eyes work? ...
Effectively Visualizing Library Data
National Research Council Canada - National Science Library
Phetteplace, Eric
2012-01-01
....6 The North Carolina State University Libraries have an ambitious data visualization project that aims to visualize the usage of reference services, course tools, computer workstations, and group study rooms...
Visualization of Social Networks
Boertjes, E.M.; Kotterink, B.; Jager, E.J.
2011-01-01
Current visualizations of social networks are mostly some form of node-link diagram. Depending on the type of social network, this can be some treevisualization with a strict hierarchical structure or a more generic network visualization.
Full Text Available ... eye diseases, visual disorders, mechanisms of visual function, preservation of sight, and the special health problems and ... Clinical Studies Publications Catalog Photos and Images Spanish Language Information Grants and Funding Extramural Research Division of ...
... eye diseases, visual disorders, mechanisms of visual function, preservation of sight, and the special health problems and ... Clinical Studies Publications Catalog Photos and Images Spanish Language Information Grants and Funding Extramural Research Division of ...
Creativity, visualization abilities, and visual cognitive style.
Kozhevnikov, Maria; Kozhevnikov, Michael; Yu, Chen Jiao; Blazhenkova, Olesya
2013-06-01
Despite the recent evidence for a multi-component nature of both visual imagery and creativity, there have been no systematic studies on how the different dimensions of creativity and imagery might interrelate. The main goal of this study was to investigate the relationship between different dimensions of creativity (artistic and scientific) and dimensions of visualization abilities and styles (object and spatial). In addition, we compared the contributions of object and spatial visualization abilities versus corresponding styles to scientific and artistic dimensions of creativity. Twenty-four undergraduate students (12 females) were recruited for the first study, and 75 additional participants (36 females) were recruited for an additional experiment. Participants were administered a number of object and spatial visualization abilities and style assessments as well as a number of artistic and scientific creativity tests. The results show that object visualization relates to artistic creativity and spatial visualization relates to scientific creativity, while both are distinct from verbal creativity. Furthermore, our findings demonstrate that style predicts corresponding dimension of creativity even after removing shared variance between style and visualization ability. The results suggest that styles might be a more ecologically valid construct in predicting real-life creative behaviour, such as performance in different professional domains. © 2013 The British Psychological Society.
Visual experience and blindsight
DEFF Research Database (Denmark)
Overgaard, Morten
2011-01-01
Blindsight is classically defined as residual visual capacity, e.g., to detect and identify visual stimuli, in the total absence of perceptual awareness following lesions to V1. However, whereas most experiments have investigated what blindsight patients can and cannot do, the literature contains...... several, often contradictory, remarks about remaining visual experience. This review examines closer these remarks as well as experiments that directly approach the nature of possibly spared visual experiences in blindsight....
Visual explorer facilitator's guide
Palus, Charles J
2010-01-01
Grounded in research and practice, the Visual Explorer™ Facilitator's Guide provides a method for supporting collaborative, creative conversations about complex issues through the power of images. The guide is available as a component in the Visual Explorer Facilitator's Letter-sized Set, Visual Explorer Facilitator's Post card-sized Set, Visual Explorer Playing Card-sized Set, and is also available as a stand-alone title for purchase to assist multiple tool users in an organization.
International Development Research Centre (IDRC) Digital Library (Canada)
Office 2004 Test Drive User
1. 10 Data Visualization Tips. Data visualizations are an effective tool to communicate research. But to realize their potential, designers should follow these tips to help readers decode their visualizations. 1. Keep it simple! This is the golden rule. Always choose the simplest way to convey your information. 2. Have a specific ...
NEON VISUALIZATION ENVIRONMENT
2017-07-28
INTRODUCTION .................................................................................................................. 1 3. METHODS... INTRODUCTION Neon is a novel departure from conventional information visualization: the goal was not to develop a typical visualization toolkit but instead...development philosophies . We assisted in creating a demo using Neon and VINI STTR tools as a visualization mechanism for MUSE. With Memex, we
The countryside visual resource
Sally Schauman
1979-01-01
This paper identifies the types of visual resource changes occurring in rural landscapes. These types include changes due to agricultural technology and land use patterns. The changes are described in relative dimensions of the landscape elements both as patterns and as individual visual elements. This paper relates visual resource changes to various countryside...
Visual Semiotics & Uncertainty Visualization: An Empirical Study.
MacEachren, A M; Roth, R E; O'Brien, J; Li, B; Swingley, D; Gahegan, M
2012-12-01
This paper presents two linked empirical studies focused on uncertainty visualization. The experiments are framed from two conceptual perspectives. First, a typology of uncertainty is used to delineate kinds of uncertainty matched with space, time, and attribute components of data. Second, concepts from visual semiotics are applied to characterize the kind of visual signification that is appropriate for representing those different categories of uncertainty. This framework guided the two experiments reported here. The first addresses representation intuitiveness, considering both visual variables and iconicity of representation. The second addresses relative performance of the most intuitive abstract and iconic representations of uncertainty on a map reading task. Combined results suggest initial guidelines for representing uncertainty and discussion focuses on practical applicability of results.
Willis, Thearon
2010-01-01
A focused, step-by-step approach to Visual Basic for new programmers. What better way to get started with Visual Basic than with this essential Wrox beginner's guide? Beginning Microsoft Visual Basic 2010 not only shows you how to write Windows applications, Web applications with ASP.NET, and Windows mobile and embedded CE apps with Visual Basic 2010, but you'll also get a thorough grounding in the basic nuts-and-bolts of writing good code. You'll be exposed to the very latest VB tools and techniques with coverage of both the Visual Studio 2010 and .NET 4 releases. Plus, the book walks you ste
Python data visualization cookbook
Milovanovic, Igor
2013-01-01
This book is written in a Cookbook style targeted towards an advanced audience. It covers the advanced topics of data visualization in Python.Python Data Visualization Cookbook is for developers that already know about Python programming in general. If you have heard about data visualization but you don't know where to start, then this book will guide you from the start and help you understand data, data formats, data visualization, and how to use Python to visualize data.You will need to know some general programming concepts, and any kind of programming experience will be helpful, but the co
Sugimoto, Azusa; Futamura, Akinori; Kawamura, Mitsuru
2011-10-01
Progressive visual agnosia was discovered in the 20th century following the discovery of classical non-progressive visual agnosia. In contrast to the classical type, which is caused by cerebral vascular disease or traumatic injury, progressive visual agnosia is a symptom of neurological degeneration. The condition of progressive visual loss, including visual agnosia, and posterior cerebral atrophy was named posterior cortical atrophy (PCA) by Benson et al. (1988). Progressive visual agnosia is also observed in semantic dementia (SD) and other degenerative diseases, but there is a difference in the subtype of visual agnosia associated with these diseases. Lissauer (1890) classified visual agnosia into apperceptive and associative types, and it in most cases, PCA is associated with the apperceptive type. However, SD patients exhibit symptoms of associative visual agnosia before changing to those of semantic memory disorder. Insights into progressive visual agnosia have helped us understand the visual system and discover how we "perceive" the outer world neuronally, with regard to consciousness. Although PCA is a type of atypical dementia, its diagnosis is important to enable patients to live better lives with appropriate functional support.
Zhou, Zhi; Arce, Gonzalo R; Di Crescenzo, Giovanni
2006-08-01
Visual cryptography encodes a secret binary image (SI) into n shares of random binary patterns. If the shares are xeroxed onto transparencies, the secret image can be visually decoded by superimposing a qualified subset of transparencies, but no secret information can be obtained from the superposition of a forbidden subset. The binary patterns of the n shares, however, have no visual meaning and hinder the objectives of visual cryptography. Extended visual cryptography [1] was proposed recently to construct meaningful binary images as shares using hypergraph colourings, but the visual quality is poor. In this paper, a novel technique named halftone visual cryptography is proposed to achieve visual cryptography via halftoning. Based on the blue-noise dithering principles, the proposed method utilizes the void and cluster algorithm [2] to encode a secret binary image into n halftone shares (images) carrying significant visual information. The simulation shows that the visual quality of the obtained halftone shares are observably better than that attained by any available visual cryptography method known to date.
Agarwal, K; Bronstein, A M; Faldon, M E; Mandalà, M; Murray, K; Silove, Y
2012-06-01
The increased visual dependence noted in some vestibular patients may be secondary to their vertigo. We examine whether a single, brief vertigo attack, such as in benign paroxysmal positional vertigo (BPPV), modifies visual dependency. Visual dependency was measured before and after the Hallpike manoeuvre with (a) the Rod and Frame and the Rod and Disc techniques whilst seated and (b) the postural sway induced by visual roll-motion stimulation. Three subject groups were studied: 20 patients with BPPV (history and positive Hallpike manoeuvre; PosH group), 20 control patients (history of BPPV but negative Hallpike manoeuvre; NegH group) and 20 normal controls. Our findings show that while both patient groups showed enhanced visual dependency, the PosH and the normal control group decreased visual dependency on repetition of the visual tasks after the Hallpike manoeuvre. NegH patients differed from PosH patients in that their high visual dependency did not diminish on repetition of the visual stimuli; they scored higher on the situational characteristic questionnaire ('visual vertigo' symptoms) and showed higher incidence of migraine. We conclude that long term vestibular symptoms increase visual dependence but a single BPPV attack does not increase it further. Repetitive visual motion stimulation induces adaptation in visual dependence in peripheral vestibular disorders such as BPPV. A positional form of vestibular migraine may underlie the symptoms of some patients with a history of BPPV but negative Hallpike manoeuvre. The finding that they have non adaptable increased visual dependency may explain visuo-vestibular symptoms in this group and, perhaps more widely, in patients with migraine.
Visualizer cognitive style enhances visual creativity.
Palmiero, Massimiliano; Nori, Raffaella; Piccardi, Laura
2016-02-26
In the last two decades, interest towards creativity has increased significantly since it was recognized as a skill and as a cognitive reserve and is now always more frequently used in ageing training. Here, the relationships between visual creativity and Visualization-Verbalization cognitive style were investigated. Fifty college students were administered the Creative Synthesis Task aimed at measuring the ability to construct creative objects and the Visualization-Verbalization Questionnaire (VVQ) aimed at measuring the attitude to preferentially use either imagery or verbal strategy while processing information. Analyses showed that only the originality score of inventions was positively predicted by the VVQ score: higher VVQ score (indicating the preference to use imagery) predicted originality of inventions. These results showed that the visualization strategy is involved especially in the originality dimension of creative objects production. In light of neuroimaging results, the possibility that different strategies, such those that involve motor processes, affect visual creativity is also discussed. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.
Ni, Ming-Jiu; Li, Jun-Feng
2012-01-01
The consistent and conservative scheme developed on a rectangular collocated mesh [M.-J. Ni, R. Munipalli, N.B. Morley, P. Huang, M.A. Abdou, A current density conservative scheme for incompressible MHD flows at a low magnetic Reynolds number. Part I: on a rectangular collocated grid system, Journal of Computational Physics 227 (2007) 174-204] and on an arbitrary collocated mesh [M.-J. Ni, R. Munipalli, P. Huang, N.B. Morley, M.A. Abdou, A current density conservative scheme for incompressible MHD flows at a low magnetic Reynolds number. Part II: on an arbitrary collocated mesh, Journal of Computational Physics 227 (2007) 205-228] has been extended and specially designed for calculation of the Lorentz force on a staggered grid system (Part III) by solving the electrical potential equation for magnetohydrodynamics (MHD) at a low magnetic Reynolds number. In a staggered mesh, pressure ( p) and electrical potential ( φ) are located in the cell center, while velocities and current fluxes are located on the cell faces of a main control volume. The scheme numerically meets the physical conservation laws, charge conservation law and momentum conservation law. Physically, the Lorentz force conserves the momentum when the magnetic field is constant or spatial coordinate independent. The calculation of current density fluxes on cell faces is conducted using a scheme consistent with the discretization for solution of the electrical potential Poisson equation, which can ensure the calculated current density conserves the charge. A divergence formula of the Lorentz force is used to calculate the Lorentz force at the cell center of a main control volume, which can numerically conserve the momentum at constant or spatial coordinate independent magnetic field. The calculated cell-center Lorentz forces are then interpolated to the cell faces, which are used to obtain the corresponding velocity fluxes by solving the momentum equations. The "conservative" is an important property of
Bidot, S; Biotti, D
2016-06-01
Migraine with visual aura is marked by recurrent episodes of transient visual disturbance, often followed by headaches. Its pathophysiology has not been fully understood, but visual auras might be related to a self-propagating wave of cortical depolarization called "cortical spreading depression", triggering a trigemino-vascular "storm" ultimately leading to headaches. The most specific visual symptom is the "fortification spectrum" consisting of glimmering jagged lines spreading from the center to the periphery, and leaving a transient scotoma in its wake. Other visual symptoms are numerous, ranging from elementary positive or negative visual phenomena to complex and elaborate hallucinations. The diagnosis can be made according to the International Classification of Headache Disorders revised in 2013. The main goal of the treatment is to relieve the patient's pain quickly and to decrease the frequency of the episodes. Copyright © 2016 Elsevier Masson SAS. All rights reserved.
Attention and visual memory in visualization and computer graphics.
Healey, Christopher G; Enns, James T
2012-07-01
A fundamental goal of visualization is to produce images of data that support visual analysis, exploration, and discovery of novel insights. An important consideration during visualization design is the role of human visual perception. How we "see" details in an image can directly impact a viewer's efficiency and effectiveness. This paper surveys research on attention and visual perception, with a specific focus on results that have direct relevance to visualization and visual analytics. We discuss theories of low-level visual perception, then show how these findings form a foundation for more recent work on visual memory and visual attention. We conclude with a brief overview of how knowledge of visual attention and visual memory is being applied in visualization and graphics. We also discuss how challenges in visualization are motivating research in psychophysics.
Progress in Scientific Visualization
Energy Technology Data Exchange (ETDEWEB)
Max, N
2004-11-15
Visualization of observed data or simulation output is important to science and engineering. I have been particularly interested in visualizing 3-D structures, and report here my personal impressions on progress in the last 20 years in visualizing molecules, scalar fields, and vector fields and their associated flows. I have tried to keep the survey and list of references manageable, so apologize to those authors whose techniques I have not mentioned, or have described without a reference citation.
Baisley, R. L.
1973-01-01
The helicopter visual aid system has been built and flight tested in situations representative of actual flight missions. The mechanisms discussed contributed greatly to the successful performance of the system throughout the 160 hours of flight testing. It has demonstrated that the visual aid concept can provide improved daytime visual capability, greatly improved nighttime capability, surveillance from greater distances and/or altitudes, covert operation at night through the use of the IR searchlight, and a photographic recording at the scene being viewed.
Cole, G F; Hungerford, J.; Jones, R B
1984-01-01
Sixteen blind babies who were considered to be showing the characteristics of delayed visual maturation were studied prospectively. The diagnosis was made on clinical grounds, and the criteria for this are discussed. All of these infants developed visual responses between 4 and 6 months of age and had normal or near normal visual acuities by 1 year of age. Long term follow up, however, has shown neurological abnormalities in some of these children.
Does visual expertise improve visual recognition memory?
Evans, Karla K; Cohen, Michael A; Tambouret, Rosemary; Horowitz, Todd; Kreindel, Erica; Wolfe, Jeremy M
2011-01-01
In general, humans have impressive recognition memory for previously viewed pictures. Many people spend years becoming experts in highly specialized image sets. For example, cytologists are experts at searching micrographs filled with potentially cancerous cells and radiologists are expert at searching mammograms for indications of cancer. Do these experts develop robust visual long-term memory for their domain of expertise? If so, is this expertise specific to the trained image class, or do such experts possess generally superior visual memory? We tested recognition memory of cytologists, radiologists, and controls with no medical experience for three visual stimulus classes: isolated objects, scenes, and mammograms or micrographs. Experts were better than control observers at recognizing images from their domain, but their memory for those images was not particularly good (D' ~ 1.0) and was much worse than memory for objects or scenes (D' > 2.0). Furthermore, experts were not better at recognizing scenes or isolated objects than control observers.
Visual computing scientific visualization and imaging systems
2014-01-01
This volume aims to stimulate discussions on research involving the use of data and digital images as an understanding approach for analysis and visualization of phenomena and experiments. The emphasis is put not only on graphically representing data as a way of increasing its visual analysis, but also on the imaging systems which contribute greatly to the comprehension of real cases. Scientific Visualization and Imaging Systems encompass multidisciplinary areas, with applications in many knowledge fields such as Engineering, Medicine, Material Science, Physics, Geology, Geographic Information Systems, among others. This book is a selection of 13 revised and extended research papers presented in the International Conference on Advanced Computational Engineering and Experimenting -ACE-X conferences 2010 (Paris), 2011 (Algarve), 2012 (Istanbul) and 2013 (Madrid). The examples were particularly chosen from materials research, medical applications, general concepts applied in simulations and image analysis and ot...
Visual languages and applications
Zhang, Kang
2010-01-01
Visual languages have long been a pursuit of effective communication between human and machine. With rapid advances of the Internet and Web technology, human-human communication through the Web or electronic mobile devices is becoming more and more prevalent. Visual Languages and Applications is a comprehensive introduction to diagrammatical visual languages. This book discusses what visual programming languages are, and how such languages and their underlying foundations can be usefully applied to other fields in computer science. It also covers a broad range of contents from the underlying t
Visualization in modern cartography
MacEachren, AM
1994-01-01
Visualization in Modern Cartography explores links between the centuries-old discipline of cartography and today's revolutionary developments in scientific visualization. The book has three main goals: (1) to pass on design and symbolization expertise to the scientific visualization community - information that comes from centuries of pre-computer visualization by cartographers, and their more recent experiences with computerizing the discipline; (2) to help cartographers cope with the dramatic shift from print cartography to a dynamic virtual cartography for which their role is changing from
Energy Technology Data Exchange (ETDEWEB)
Scholtz, Jean; Burtner, Edwin R.; Cook, Kristin A.
2016-06-13
This course will introduce the field of Visual Analytics to HCI researchers and practitioners highlighting the contributions they can make to this field. Topics will include a definition of visual analytics along with examples of current systems, types of tasks and end users, issues in defining user requirements, design of visualizations and interactions, guidelines and heuristics, the current state of user-centered evaluations, and metrics for evaluation. We encourage designers, HCI researchers, and HCI practitioners to attend to learn how their skills can contribute to advancing the state of the art of visual analytics
Miras, Thomas
2013-01-01
This study deals with the coupling between an incompressible, irrotational fluid and an elastic container in the context of small amplitude vibrations.Firstly, we present a method to introduce the viscous dissipative sources in the liquid directly from the equations of the conservative coupled problem using a fluid potential approach generally used to treat linear undamped problems. A diagonal damping model is chosen for the liquid and its dissipative effects are taken into account through mo...
Personal Visualization and Personal Visual Analytics.
Huang, Dandan; Tory, Melanie; Aseniero, Bon Adriel; Bartram, Lyn; Bateman, Scott; Carpendale, Sheelagh; Tang, Anthony; Woodbury, Robert
2015-03-01
Data surrounds each and every one of us in our daily lives, ranging from exercise logs, to archives of our interactions with others on social media, to online resources pertaining to our hobbies. There is enormous potential for us to use these data to understand ourselves better and make positive changes in our lives. Visualization (Vis) and visual analytics (VA) offer substantial opportunities to help individuals gain insights about themselves, their communities and their interests; however, designing tools to support data analysis in non-professional life brings a unique set of research and design challenges. We investigate the requirements and research directions required to take full advantage of Vis and VA in a personal context. We develop a taxonomy of design dimensions to provide a coherent vocabulary for discussing personal visualization and personal visual analytics. By identifying and exploring clusters in the design space, we discuss challenges and share perspectives on future research. This work brings together research that was previously scattered across disciplines. Our goal is to call research attention to this space and engage researchers to explore the enabling techniques and technology that will support people to better understand data relevant to their personal lives, interests, and needs.
Visual Checking of Spreadsheets
Chen, Ying; Chan, Hock Chuan
2008-01-01
The difference between surface and deep structures of a spreadsheet is a major cause of difficulty in checking spreadsheets. After a brief survey of current methods of checking (or debugging) spreadsheets, new visual methods of showing the deep structures are presented. Illustrations are given on how these visual methods can be employed in various interactive local and global debugging strategies.
McLester, Susan
2006-01-01
A major influence this generation of high school digital natives has had on the curriculum is their natural focus on visuals to convey information. They are driving the move toward visual information. In this article, one high school expands the learning environment from handhelds to videoconferencing. Sacred Heart has found that mixing the…
Mathematica data visualization
Saquib, Nazmus
2014-01-01
If you are planning to create data analysis and visualization tools in the context of science, engineering, economics, or social science, then this book is for you. With this book, you will become a visualization expert, in a short time, using Mathematica.
Full Text Available ... Institute’s mission is to “conduct and support research, training, health information dissemination, and other programs with respect to blinding eye diseases, visual disorders, mechanisms of visual function, preservation of sight, and the special health problems ...
Full Text Available ... Vision Research & Ophthalmology (DIVRO) Student Training Programs To search for current job openings visit HHS USAJobs Home > NEI for Kids > The Visual System All About Vision About the Eye Ask a Scientist Video Series Glossary The Visual System Your Eyes’ ...
Gatta, Oriana
2013-01-01
As an advanced rhetoric and composition doctoral student, I taught Engl 3135: Visual Rhetoric, a three-credit upper-level course offered by the Department of English at Georgia State University. Mary E. Hocks originally designed this course in 2000 to, in her words, "introduce visual information design theories and practices for writers [and]…
Visualizing Qualitative Information
Slone, Debra J.
2009-01-01
The abundance of qualitative data in today's society and the need to easily scrutinize, digest, and share this information calls for effective visualization and analysis tools. Yet, no existing qualitative tools have the analytic power, visual effectiveness, and universality of familiar quantitative instruments like bar charts, scatter-plots, and…
Merlyn J. Paulson
1979-01-01
This paper outlines a project level process (V.I.S.) which utilizes very accurate and flexible computer algorithms in combination with contemporary site analysis and design techniques for visual evaluation, design and management. The process provides logical direction and connecting bridges through problem identification, information collection and verification, visual...
Normalized medical information visualization.
Sánchez-de-Madariaga, Ricardo; Muñoz, Adolfo; Somolinos, Roberto; Castro, Antonio; Velázquez, Iker; Moreno, Oscar; García-Pacheco, José L; Pascual, Mario; Salvador, Carlos H
2015-01-01
A new mark-up programming language is introduced in order to facilitate and improve the visualization of ISO/EN 13606 dual model-based normalized medical information. This is the first time that visualization of normalized medical information is addressed and the programming language is intended to be used by medical non-IT professionals.
Full Text Available ... blinding eye diseases, visual disorders, mechanisms of visual function, preservation of sight, and the special health problems ... Lead joe.balintfy@nih.gov Anna Harper - Media Relations afh@nei.nih.gov NEI Office of Communications (301)496-5248 ... This website is maintained by the NEI Office of Science Communications, Public Liaison, and Education. Technical questions about this website ...
Disorders of visual perception
Ffytche, Dominic H.; Blom, J. D.; Catani, M.
2010-01-01
Visual perceptual disorders are often presented as a disparate group of neurological deficits with little consideration given to the wide range of visual symptoms found in psychiatric and neurodevelopmental disease. Here, the authors attempt a functional anatomical classification of all disorders
Wade, Nicholas J
2008-01-01
The art of visual communication is not restricted to the fine arts. Scientists also apply art in communicating their ideas graphically. Diagrams of anatomical structures, like the eye and visual pathways, and figures displaying specific visual phenomena have assisted in the communication of visual ideas for centuries. It is often the case that the development of a discipline can be traced through graphical representations and this is explored here in the context of concepts of visual science. As with any science, vision can be subdivided in a variety of ways. The classification adopted is in terms of optics, anatomy, and visual phenomena; each of these can in turn be further subdivided. Optics can be considered in terms of the nature of light and its transmission through the eye. Understanding of the gross anatomy of the eye and visual pathways was initially dependent upon the skills of the anatomist whereas microanatomy relied to a large extent on the instruments that could resolve cellular detail, allied to the observational skills of the microscopist. Visual phenomena could often be displayed on the printed page, although novel instruments expanded the scope of seeing, particularly in the nineteenth century.
Critical Reading: Visual Skills.
Adams, Dennis M.
The computer controlled visual media, particularly television, are becoming an increasingly powerful instrument for the manipulation of thought. Powerful visual images increasingly reflect and shape personal and external reality--politics being one such example--and it is crucial that the viewing public understand the nature of these media…
Music Alters Visual Perception
Jolij, Jacob; Meurs, Maaike
2011-01-01
Background: Visual perception is not a passive process: in order to efficiently process visual input, the brain actively uses previous knowledge (e. g., memory) and expectations about what the world should look like. However, perception is not only influenced by previous knowledge. Especially the
VISUAL DISTRACTION WHILE DRIVING
Directory of Open Access Journals (Sweden)
Hajime ITO
2001-01-01
The article provides background information and summarizes worldwide trends in research on accident rates, the special characteristics of visual behavior and the effects of visual distraction on drivers and vehicle behavior. It also reports on the state of ISO standardization efforts and related technological trends. Finally, it defines a number of topics for future research in the field of human engineering.
Lee Anderson; Jerry Mosier; Geoffrey Chandler
1979-01-01
Visual absorption capability (VAC) is a tool to assess a landscape's susceptibility to visual change caused by man's activities. This paper explores different descriptive approaches to VAC and addresses in depth the development of the VAC process used on the Klamath National Forest. Four biophysical factors were selected to assess VAC for the lands within the...
Donderi, Don C.
2006-01-01
The idea of visual complexity, the history of its measurement, and its implications for behavior are reviewed, starting with structuralism and Gestalt psychology at the beginning of the 20th century and ending with visual complexity theory, perceptual learning theory, and neural circuit theory at the beginning of the 21st. Evidence is drawn from…
Visualizing Dynamic Memory Allocations
Moreta, Sergio; Telea, Alexandru
2007-01-01
We present a visualization tool for dynamic memory allocation information obtained from instrumenting the runtime allocator used by C programs. The goal of the presented visualization techniques is to convey insight in the dynamic behavior of the allocator. The purpose is to help the allocator
Network Visualization Project (NVP)
2016-07-01
4 This makes for an intuitive and aesthetically pleasing graph drawing that is easy to learn and manipulate . Aside from the visual aspects of the...Fig. 7). From here, there are multiple controls to interact with as well as the visualization itself. The time line can be manipulated freely...
Range management visual impacts
Bruce R. Brown; David Kissel
1979-01-01
Historical overgrazing of western public rangelands has resulted in the passage of the Public Rangeland Improvement Act of 1978. The main purpose of this Act is to improve unsatisfactory range conditions. A contributing factor to unfavorable range conditions is adverse visual impacts. These visual impacts can be identified in three categories of range management: range...
Exploring the Visual Landscape
Nijhuis, S.; Van Lammeren, R.; Van der Hoeven, F.
2011-01-01
Exploring the Visual Landscape is about the combination of landscape research and planning, visual perception and Geographic Information Science. It showcases possible ways of getting a grip on themes like: landscape openness, cluttering of the rural landscape, high-rise buildings in relation to
Harel, S; Holtzman, M; Feinsod, M
1983-01-01
Three infants, recognised as blind during the first 4 months of life, were found to be normal on neurological and ophthalmological examinations. Visual electro-diagnostic studies showed normal retinal responses, but delayed conduction velocities and impaired visually-evoked responses over the occipital cortex. After age 6 months, normal vision developed gradually and all abnormalities disappeared.
Harel, S; Holtzman, M; Feinsod, M
1983-01-01
Three infants, recognised as blind during the first 4 months of life, were found to be normal on neurological and ophthalmological examinations. Visual electro-diagnostic studies showed normal retinal responses, but delayed conduction velocities and impaired visually-evoked responses over the occipital cortex. After age 6 months, normal vision developed gradually and all abnormalities disappeared. PMID:6189454
Xenakis, A M; Lind, S J; Stansby, P K; Rogers, B D
2017-03-01
Tsunamis caused by landslides may result in significant destruction of the surroundings with both societal and industrial impact. The 1958 Lituya Bay landslide and tsunami is a recent and well-documented terrestrial landslide generating a tsunami with a run-up of 524 m. Although recent computational techniques have shown good performance in the estimation of the run-up height, they fail to capture all the physical processes, in particular, the landslide-entry profile and interaction with the water. Smoothed particle hydrodynamics (SPH) is a versatile numerical technique for describing free-surface and multi-phase flows, particularly those that exhibit highly nonlinear deformation in landslide-generated tsunamis. In the current work, the novel multi-phase incompressible SPH method with shifting is applied to the Lituya Bay tsunami and landslide and is the first methodology able to reproduce realistically both the run-up and landslide-entry as documented in a benchmark experiment. The method is the first paper to develop a realistic implementation of the physics that in addition to the non-Newtonian rheology of the landslide includes turbulence in the water phase and soil saturation. Sensitivity to the experimental initial conditions is also considered. This work demonstrates the ability of the proposed method in modelling challenging environmental multi-phase, non-Newtonian and turbulent flows.
Fehn, Niklas; Wall, Wolfgang A.; Kronbichler, Martin
2017-12-01
The present paper deals with the numerical solution of the incompressible Navier-Stokes equations using high-order discontinuous Galerkin (DG) methods for discretization in space. For DG methods applied to the dual splitting projection method, instabilities have recently been reported that occur for small time step sizes. Since the critical time step size depends on the viscosity and the spatial resolution, these instabilities limit the robustness of the Navier-Stokes solver in case of complex engineering applications characterized by coarse spatial resolutions and small viscosities. By means of numerical investigation we give evidence that these instabilities are related to the discontinuous Galerkin formulation of the velocity divergence term and the pressure gradient term that couple velocity and pressure. Integration by parts of these terms with a suitable definition of boundary conditions is required in order to obtain a stable and robust method. Since the intermediate velocity field does not fulfill the boundary conditions prescribed for the velocity, a consistent boundary condition is derived from the convective step of the dual splitting scheme to ensure high-order accuracy with respect to the temporal discretization. This new formulation is stable in the limit of small time steps for both equal-order and mixed-order polynomial approximations. Although the dual splitting scheme itself includes inf-sup stabilizing contributions, we demonstrate that spurious pressure oscillations appear for equal-order polynomials and small time steps highlighting the necessity to consider inf-sup stability explicitly.
D'Alessandro, Valerio; Binci, Lorenzo; Montelpare, Sergio; Ricci, Renato
2018-01-01
Open-source CFD codes provide suitable environments for implementing and testing low-dissipative algorithms typically used to simulate turbulence. In this research work we developed CFD solvers for incompressible flows based on high-order explicit and diagonally implicit Runge-Kutta (RK) schemes for time integration. In particular, an iterated PISO-like procedure based on Rhie-Chow correction was used to handle pressure-velocity coupling within each implicit RK stage. For the explicit approach, a projected scheme was used to avoid the "checker-board" effect. The above-mentioned approaches were also extended to flow problems involving heat transfer. It is worth noting that the numerical technology available in the OpenFOAM library was used for space discretization. In this work, we additionally explore the reliability and effectiveness of the proposed implementations by computing several unsteady flow benchmarks; we also show that the numerical diffusion due to the time integration approach is completely canceled using the solution techniques proposed here.
Krank, Benjamin; Fehn, Niklas; Wall, Wolfgang A.; Kronbichler, Martin
2017-11-01
We present an efficient discontinuous Galerkin scheme for simulation of the incompressible Navier-Stokes equations including laminar and turbulent flow. We consider a semi-explicit high-order velocity-correction method for time integration as well as nodal equal-order discretizations for velocity and pressure. The non-linear convective term is treated explicitly while a linear system is solved for the pressure Poisson equation and the viscous term. The key feature of our solver is a consistent penalty term reducing the local divergence error in order to overcome recently reported instabilities in spatially under-resolved high-Reynolds-number flows as well as small time steps. This penalty method is similar to the grad-div stabilization widely used in continuous finite elements. We further review and compare our method to several other techniques recently proposed in literature to stabilize the method for such flow configurations. The solver is specifically designed for large-scale computations through matrix-free linear solvers including efficient preconditioning strategies and tensor-product elements, which have allowed us to scale this code up to 34.4 billion degrees of freedom and 147,456 CPU cores. We validate our code and demonstrate optimal convergence rates with laminar flows present in a vortex problem and flow past a cylinder and show applicability of our solver to direct numerical simulation as well as implicit large-eddy simulation of turbulent channel flow at Reτ = 180 as well as 590.
Yang, Xuguang; Shi, Baochang; Chai, Zhenhua
2014-07-01
In this paper, two modified lattice Boltzmann Bhatnagar-Gross-Krook (LBGK) models for incompressible Navier-Stokes equations and convection-diffusion equations are proposed via the addition of correction terms in the evolution equations. Utilizing this modification, the value of the dimensionless relaxation time in the LBGK model can be kept in a proper range, and thus the stability of the LBGK model can be improved. Although some gradient operators are included in the correction terms, they can be computed efficiently using local computational schemes such that the present LBGK models still retain the intrinsic parallelism characteristic of the lattice Boltzmann method. Numerical studies of the steady Poiseuille flow and unsteady Womersley flow show that the modified LBGK model has a second-order convergence rate in space, and the compressibility effect in the common LBGK model can be eliminated. In addition, to test the stability of the present models, we also performed some simulations of the natural convection in a square cavity, and we found that the results agree well with those reported in the previous work, even at a very high Rayleigh number (Ra = 10(12)).
Visualization and mathematics III
Polthier, Konrad
2003-01-01
This research book on Mathematical Visualization contains state of the art presentations on visualization problems in mathematics, on fundamental mathematical research in computer graphics, and on software frameworks for the application of visualization to real-world problems. All contributions were written by leading experts in the field and peer-refereed by an international editorial team. The book grew out of the third international workshop "Visualization and Mathematics", which was held from May 22-25, 2002 in Berlin. The themes of the book cover important recent developments on - Geometry and Combinatorics of Meshes - Discrete Vector Fields and Topology - Geometric Modelling - Image Based Visualization - Software Environments and Applications - Education and Communication The variety of topics makes the book a suitable resource for researchers, lecturers, and practitioners; http://www-sfb288.math.tu-berlin.de/vismath/
Houdini for Astrophysical Visualization
Naiman, J. P.; Borkiewicz, Kalina; Christensen, A. J.
2017-05-01
The rapid growth in scale and complexity of both computational and observational astrophysics over the past decade necessitates efficient and intuitive methods for examining and visualizing large data sets. Here, we discuss some newly developed tools used to import and manipulate astrophysical data into the three-dimensional visual effects software, Houdini. This software is widely used by visual effects artists, but a recently implemented Python API now allows astronomers to more easily use Houdini as a visualization tool. This paper includes a description of features, workflow, and various example visualizations. The project website, www.ytini.com, is aimed at a scientific audience and contains Houdini tutorials and links to the Python script Bitbucket repository to simplify the process of importing and rendering astrophysical data.
Directory of Open Access Journals (Sweden)
Helle Rexbye
2007-07-01
Full Text Available Consumer culture has placed the ageing body in a dilemma of representation. Physical appearance has become increasingly important as a symbol of identity, and at the same time society idealizes youth. This study explores visual ageing empirically. By using photographs of older persons (70+ as starting point, it is explored how visual age is assessed and interpreted. It is shown that informants read age in a spread of stages and categories. Main age indicators are biological markers: skin, eyes, and hair colour, but supplemented by vigour, style, and grooming. Furthermore, in-depth interviews indicate that visual age is mainly interpreted into categories and moral regulations rooted in early modernity. Subsequently the question of a postmodern perspective of visual ageing is discussed in this article. The empirical findings in the study question a postmodern fluidity of visual signs – at least when the concern is signs of ageing.
Visualization of Social Networks
Chen, Ing-Xiang; Yang, Cheng-Zen
With the ubiquitous characteristic of the Internet, today many online social environments are provided to connect people. Various social relationships are thus created, connected, and migrated from our real lives to the Internet environment from different social groups. Many social communities and relationships are also quickly constructed and connected via instant personal messengers, blogs, Twitter, Facebook, and a great variety of online social services. Since social network visualizations can structure the complex relationships between different groups of individuals or organizations, they are helpful to analyze the social activities and relationships of actors, particularly over a large number of nodes. Therefore, many studies and visualization tools have been investigated to present social networks with graph representations. In this chapter, we will first review the background of social network analysis and visualization methods, and then introduce various novel visualization applications for social networks. Finally, the challenges and the future development of visualizing online social networks are discussed.
Visualization of JPEG Metadata
Malik Mohamad, Kamaruddin; Deris, Mustafa Mat
There are a lot of information embedded in JPEG image than just graphics. Visualization of its metadata would benefit digital forensic investigator to view embedded data including corrupted image where no graphics can be displayed in order to assist in evidence collection for cases such as child pornography or steganography. There are already available tools such as metadata readers, editors and extraction tools but mostly focusing on visualizing attribute information of JPEG Exif. However, none have been done to visualize metadata by consolidating markers summary, header structure, Huffman table and quantization table in a single program. In this paper, metadata visualization is done by developing a program that able to summarize all existing markers, header structure, Huffman table and quantization table in JPEG. The result shows that visualization of metadata helps viewing the hidden information within JPEG more easily.
Interactive Data Visualization
Energy Technology Data Exchange (ETDEWEB)
Steed, Chad A [ORNL
2017-01-01
Interactive data visualization leverages human visual perception and cognition to improve the accuracy and effectiveness of data analysis. When combined with automated data analytics, data visualization systems orchestrate the strengths of humans with the computational power of machines to solve problems neither approach can manage in isolation. In the intelligent transportation system domain, such systems are necessary to support decision making in large and complex data streams. In this chapter, we provide an introduction to several key topics related to the design of data visualization systems. In addition to an overview of key techniques and strategies, we will describe practical design principles. The chapter is concluded with a detailed case study involving the design of a multivariate visualization tool.
Morin, P; Rivrain, Y; Eustache, F; Lambert, J; Courtheoux, P
1984-01-01
A patient presented with visual and tactile agnosia due to a spontaneous left occipito-temporal hematoma. Major memory and spatial orientation disorders were also noted, but language, gestures, auditory and olfactory perception, and interior visual imagerie were unaffected. A review of the literature since 1970 found 6 cases of an association of this type among 17 patients with visual agnosia. There appears to be no relationship between the presence of tactile agnosia and the global or partial character of the visual agnosia, the severity of memory disturbances, the presence of visuoverbal disconnection or visual imagery disorders. In contrast, these cases differed in that the lesions were more extensive and extended beyond the internal occipital regions: they were widespread in 3 cases and in the left internal occipital and parietal region in 1 case. In the patient reported in this paper there was a wide lesion of the posterior white matter of the left hemisphere.
Does visual expertise improve visual recognition memory?
Evans, Karla K.; Cohen, Michael A.; Tambouret, Rosemary; Horowitz, Todd; Kreindel, Erica; Wolfe, Jeremy M.
2011-01-01
In general, humans have impressive recognition memory for previously viewed pictures. Many people spend years becoming experts in highly specialized image sets. For example, cytologists are experts at searching micrographs filled with potentially cancerous cells and radiologists are expert at searching mammograms for indications of cancer. Do these experts develop robust visual long-term memory for their domain of expertise? If so, is this expertise specific to the trained image class, or do ...
Marmel, Elaine
2010-01-01
The complete visual reference on Excel basics. Aimed at visual learners who are seeking an all-in-one reference that provides in-depth coveage of Excel from a visual viewpoint, this resource delves into all the newest features of Excel 2010. You'll explore Excel with helpful step-by-step instructions that show you, rather than tell you, how to navigate Excel, work with PivotTables and PivotCharts, use macros to streamline work, and collaborate with other users in one document.: This two-color guide features screen shots with specific, numbered instructions so you can learn the actions you need
Marketing engagement through visual content
National Research Council Canada - National Science Library
Marius Manic
2015-01-01
Engaging visual is a must in the modern marketing world. Wide access to mass communication devices, with extended visuals enhancements, made visual content an important point of interest for any publisher, on all media channels...
Scientific visualization uncertainty, multifield, biomedical, and scalable visualization
Chen, Min; Johnson, Christopher; Kaufman, Arie; Hagen, Hans
2014-01-01
Based on the seminar that took place in Dagstuhl, Germany in June 2011, this contributed volume studies the four important topics within the scientific visualization field: uncertainty visualization, multifield visualization, biomedical visualization and scalable visualization. • Uncertainty visualization deals with uncertain data from simulations or sampled data, uncertainty due to the mathematical processes operating on the data, and uncertainty in the visual representation, • Multifield visualization addresses the need to depict multiple data at individual locations and the combination of multiple datasets, • Biomedical is a vast field with select subtopics addressed from scanning methodologies to structural applications to biological applications, • Scalability in scientific visualization is critical as data grows and computational devices range from hand-held mobile devices to exascale computational platforms. Scientific Visualization will be useful to practitioners of scientific visualization, ...
Visual imagery without visual perception: lessons from blind subjects
Bértolo, Helder
2014-08-01
The question regarding visual imagery and visual perception remain an open issue. Many studies have tried to understand if the two processes share the same mechanisms or if they are independent, using different neural substrates. Most research has been directed towards the need of activation of primary visual areas during imagery. Here we review some of the works providing evidence for both claims. It seems that studying visual imagery in blind subjects can be used as a way of answering some of those questions, namely if it is possible to have visual imagery without visual perception. We present results from the work of our group using visual activation in dreams and its relation with EEG's spectral components, showing that congenitally blind have visual contents in their dreams and are able to draw them; furthermore their Visual Activation Index is negatively correlated with EEG alpha power. This study supports the hypothesis that it is possible to have visual imagery without visual experience.
Full Text Available ... National Eye Health Education Program (NEHEP) Diabetic Eye Disease Education Program Glaucoma Education Program ... All About Vision About the Eye Ask a Scientist Video Series Glossary The Visual System Your Eyes’ Natural ...
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Principles of visual attention
DEFF Research Database (Denmark)
Bundesen, Claus; Habekost, Thomas
The nature of attention is one of the oldest and most central problems in psychology. A huge amount of research has been produced on this subject in the last half century, especially on attention in the visual modality, but a general explanation has remained elusive. Many still view attention...... research as a field that is fundamentally fragmented. This book takes a different perspective and presents a unified theory of visual attention: the TVA model. The TVA model explains the many aspects of visual attention by just two mechanisms for selection of information: filtering and pigeonholing....... These mechanisms are described in a set of simple equations, which allow TVA to mathematically model a large number of classical results in the attention literature. The theory explains psychological and neuroscientific findings by the same equations; TVA is a complete theory of visual attention, linking mind...
Full Text Available ... Video Series Glossary The Visual System Your Eyes’ Natural Defenses Eye ... is maintained by the NEI Office of Science Communications, Public Liaison, and Education. Technical questions about ...
Full Text Available ... USAJobs Home > NEI for Kids > The Visual System All About Vision About the Eye Ask a Scientist Video ... Vision Tips Protective Eyewear Sports and Your Eyes Fun Stuff Cool Eye Tricks Links to More Information ...
Full Text Available ... Tricks Links to More Information Optical Illusions Printables The Visual System Ever wonder how your eyes work? ... able to see the world around you. Did You Know? On average, you blink about 15 to ...
National Research Council Canada - National Science Library
Rosenberg, EA
2008-01-01
... and independent living for the visually impaired patient. In the United States, the four most prevalent etiologies of vision loss in persons 40 years and older are age-related macular degeneration, cataracts, glaucoma, and diabetic retinopathy...
Visualization in scientific computing
National Research Council Canada - National Science Library
Nielson, Gregory M; Shriver, Bruce D; Rosenblum, Lawrence J
1990-01-01
The purpose of this text is to provide a reference source to scientists, engineers, and students who are new to scientific visualization or who are interested in expanding their knowledge in this subject...
Full Text Available ... of the NEI NEI 50th Anniversary NEI Women Scientists Advisory Committee (WSAC) Board of Scientific Counselors National ... All About Vision About the Eye Ask a Scientist Video Series Glossary The Visual System Your Eyes’ ...
DEFF Research Database (Denmark)
Poulsen, Signe Herbers; Fjord-Larsen, Mads; Hansen, Frank Allan
This paper identifies several problems with navigating and visualizing guided tours in traditional hypermedia systems. We discuss solutions to these problems, including the representation of guided tours as 3D metro maps with content preview. Issues regarding navigation and disorientation...
Dudley, N. J.
1990-01-01
This article provides only a flavour of the type and range of aids available to the visually impaired person. Many other aids for leisure, learning, and daily living are illustrated in the RNIB equipment and games catalogue.
Full Text Available ... of visual function, preservation of sight, and the special health problems and requirements of the blind.” News & ... Emily Y. Chew, M.D., Deputy Clinical Director Education Programs National Eye Health Education Program (NEHEP) Diabetic ...
Adaptive semantics visualization
Nazemi, Kawa
2016-01-01
This book introduces a novel approach for intelligent visualizations that adapts the different visual variables and data processing to human’s behavior and given tasks. Thereby a number of new algorithms and methods are introduced to satisfy the human need of information and knowledge and enable a usable and attractive way of information acquisition. Each method and algorithm is illustrated in a replicable way to enable the reproduction of the entire “SemaVis” system or parts of it. The introduced evaluation is scientifically well-designed and performed with more than enough participants to validate the benefits of the methods. Beside the introduced new approaches and algorithms, readers may find a sophisticated literature review in Information Visualization and Visual Analytics, Semantics and information extraction, and intelligent and adaptive systems. This book is based on an awarded and distinguished doctoral thesis in computer science.
Full Text Available ... The Visual System Your Eyes’ Natural Defenses Eye Health and Safety First Aid Tips Healthy Vision Tips ... addressed to the NEI Website Manager . Department of Health and Human Services | The National Institutes of Health | ...
Edge Bundling in Information Visualization
National Research Council Canada - National Science Library
Hong Zhou Panpan Xu Xiaoru Yuan Huamin Qu
2013-01-01
The edge, which can encode relational data in graphs and multidimensional data in parallel coordinates plots, is an important visual primitive for encoding data in information visualization research...
Introduction: Visualizing Violence
Hewitson, M.
2017-01-01
The Introduction explores the relationship between visual and literary representations of modern warfare. What impact have paintings, cartoons, films and television had on the reporting of conflicts? How has the visual imagery of military violence – as the most extensive and damaging form of violence – changed? Here, Susan Sontag's 2003 essay Regarding the Pain of Others is used as a starting point for a wider discussion of what it means to portray, and to witness portrayals of, wartime viole...
Huron, Samuel; Vuillemot, Romain; Fekete, Jean-Daniel
2012-01-01
This Poster receive the Best Poster award from the IEEE INFOVIS committee.; International audience; We present Visual Sedimentation, a new design metaphor for visualizing streaming data inspired by the geological process of sedimentation. Our work started by early experiments visualiz- ing political Twitter streams during the French 2012 presidential elections, and social interactions during a TV show. In both cases, the positive feedback we received expressed an unexpectedly high level of en...
Visual Causal Feature Learning
Chalupka, Krzysztof; Perona, Pietro; Eberhardt, Frederick
2014-01-01
We provide a rigorous definition of the visual cause of a behavior that is broadly applicable to the visually driven behavior in humans, animals, neurons, robots and other perceiving systems. Our framework generalizes standard accounts of causal learning to settings in which the causal variables need to be constructed from micro-variables. We prove the Causal Coarsening Theorem, which allows us to gain causal knowledge from observational data with minimal experimental effort. The theorem prov...
Fielder, A R; Russell-Eggitt, I R; Dodd, K L; Mellor, D H
1985-01-01
Fifty-three infants with delayed visual maturation (DVM) are presented. These have been classified according to their ocular and systemic features into three groups: DVM as an isolated anomaly, in association with mental retardation, and ocular abnormalities accompanied by DVM. The clinical features are discussed, particularly regarding the time and speed of visual improvement in the three groups. Infants with DVM who experienced difficulties in the perinatal period have an increased risk of developing permanent neurological sequelae.
Visual electrophysiology in children
Directory of Open Access Journals (Sweden)
Jelka Brecelj
2005-10-01
Full Text Available Background: Electrophysiological assessment of vision in children helps to recognise abnormal development of the visual system when it is still susceptible to medication and eventual correction. Visual electrophysiology provides information about the function of the retina (retinal pigment epithelium, cone and rod receptors, bipolar, amacrine, and ganglion cells, optic nerve, chiasmal and postchiasmal visual pathway, and visual cortex.Methods: Electroretinograms (ERG and visual evoked potentials (VEP are recorded non-invasively; in infants are recorded simultaneously ERG with skin electrodes, while in older children separately ERG with HK loop electrode in accordance with ISCEV (International Society for Clinical Electrophysiology of Vision recommendations.Results: Clinical and electrophysiological changes in children with nystagmus, Leber’s congenital amaurosis, achromatopsia, congenital stationary night blindness, progressive retinal dystrophies, optic nerve hypoplasia, albinism, achiasmia, optic neuritis and visual pathway tumours are presented.Conclusions: Electrophysiological tests can help to indicate the nature and the location of dysfunction in unclear ophthalmological and/or neurological cases.
Directory of Open Access Journals (Sweden)
W Alexander Escobar
2013-11-01
Full Text Available The proposed model holds that, at its most fundamental level, visual awareness is quantized. That is to say that visual awareness arises as individual bits of awareness through the action of neural circuits with hundreds to thousands of neurons in at least the human striate cortex. Circuits with specific topologies will reproducibly result in visual awareness that correspond to basic aspects of vision like color, motion and depth. These quanta of awareness (qualia are produced by the feedforward sweep that occurs through the geniculocortical pathway but are not integrated into a conscious experience until recurrent processing from centers like V4 or V5 select the appropriate qualia being produced in V1 to create a percept. The model proposed here has the potential to shift the focus of the search for visual awareness to the level of microcircuits and these likely exist across the kingdom Animalia. Thus establishing qualia as the fundamental nature of visual awareness will not only provide a deeper understanding of awareness, but also allow for a more quantitative understanding of the evolution of visual awareness throughout the animal kingdom.
Visualization of multidimensional database
Lee, Chung
2008-01-01
The concept of multidimensional databases has been extensively researched and wildly used in actual database application. It plays an important role in contemporary information technology, but due to the complexity of its inner structure, the database design is a complicated process and users are having a hard time fully understanding and using the database. An effective visualization tool for higher dimensional information system helps database designers and users alike. Most visualization techniques focus on displaying dimensional data using spreadsheets and charts. This may be sufficient for the databases having three or fewer dimensions but for higher dimensions, various combinations of projection operations are needed and a full grasp of total database architecture is very difficult. This study reviews existing visualization techniques for multidimensional database and then proposes an alternate approach to visualize a database of any dimension by adopting the tool proposed by Kiviat for software engineering processes. In this diagramming method, each dimension is represented by one branch of concentric spikes. This paper documents a C++ based visualization tool with extensive use of OpenGL graphics library and GUI functions. Detailed examples of actual databases demonstrate the feasibility and effectiveness in visualizing multidimensional databases.
METAGRAPH VISUALIZATION METHOD
Directory of Open Access Journals (Sweden)
O. S. Kryvenko
2014-05-01
Full Text Available Analysis of visualization techniques for various types of graphs is done. Conclusion about the relevance of method development for metagraph visualizing is made. The paper deals with issues that arise when solving the problem of metagraph visualization, such as: the placement of nodes that belong to metavertices and do not belong to them, figures intersection of metavertices. These problems are exemplified. Criteria are proposed for the final image to be considered coherent, understandable for users and corresponding to a predetermined metagraph. The problem of metagraph visualization is posed. The method based on the principles of force algorithms is proposed for the problem solving. The rules for forces between metagraph nodes are defined in the framework of the method. These forces depend on nodes type between which they are performed and the presence of edges between them. This method does not involve human intervention during the formation of the image, thus saving time at frequent changes that require rebuilding of the image. The resulting image gives the possibility to portray clearly the entities of the subject area and the links between them. Graphical analysis methods can be applied to the image. Areas for the future researches are identified. They are: minimization of the number of edges intersections and the area occupied by the resulting image. Results of the modified visualization method can improve the visual metagraph representation.
Cosmography and Data Visualization
Pomarède, Daniel; Courtois, Hélène M.; Hoffman, Yehuda; Tully, R. Brent
2017-05-01
Cosmography, the study and making of maps of the universe or cosmos, is a field where visual representation benefits from modern three-dimensional visualization techniques and media. At the extragalactic distance scales, visualization is contributing to our understanding of the complex structure of the local universe in terms of spatial distribution and flows of galaxies and dark matter. In this paper, we report advances in the field of extragalactic cosmography obtained using the SDvision visualization software in the context of the Cosmicflows Project. Here, multiple visualization techniques are applied to a variety of data products: catalogs of galaxy positions and galaxy peculiar velocities, reconstructed velocity field, density field, gravitational potential field, velocity shear tensor viewed in terms of its eigenvalues and eigenvectors, envelope surfaces enclosing basins of attraction. These visualizations, implemented as high-resolution images, videos, and interactive viewers, have contributed to a number of studies: the cosmography of the local part of the universe, the nature of the Great Attractor, the discovery of the boundaries of our home supercluster of galaxies Laniakea, the mapping of the cosmic web, and the study of attractors and repellers.
Ge, Liang; Sotiropoulos, Fotis
2007-08-01
A novel numerical method is developed that integrates boundary-conforming grids with a sharp interface, immersed boundary methodology. The method is intended for simulating internal flows containing complex, moving immersed boundaries such as those encountered in several cardiovascular applications. The background domain (e.g the empty aorta) is discretized efficiently with a curvilinear boundary-fitted mesh while the complex moving immersed boundary (say a prosthetic heart valve) is treated with the sharp-interface, hybrid Cartesian/immersed-boundary approach of Gilmanov and Sotiropoulos [1]. To facilitate the implementation of this novel modeling paradigm in complex flow simulations, an accurate and efficient numerical method is developed for solving the unsteady, incompressible Navier-Stokes equations in generalized curvilinear coordinates. The method employs a novel, fully-curvilinear staggered grid discretization approach, which does not require either the explicit evaluation of the Christoffel symbols or the discretization of all three momentum equations at cell interfaces as done in previous formulations. The equations are integrated in time using an efficient, second-order accurate fractional step methodology coupled with a Jacobian-free, Newton-Krylov solver for the momentum equations and a GMRES solver enhanced with multigrid as preconditioner for the Poisson equation. Several numerical experiments are carried out on fine computational meshes to demonstrate the accuracy and efficiency of the proposed method for standard benchmark problems as well as for unsteady, pulsatile flow through a curved, pipe bend. To demonstrate the ability of the method to simulate flows with complex, moving immersed boundaries we apply it to calculate pulsatile, physiological flow through a mechanical, bileaflet heart valve mounted in a model straight aorta with an anatomical-like triple sinus.
Cheny, Yoann; Botella, Olivier
2010-02-01
This paper concerns the development of a new Cartesian grid/immersed boundary (IB) method for the computation of incompressible viscous flows in two-dimensional irregular geometries. In IB methods, the computational grid is not aligned with the irregular boundary, and of upmost importance for accuracy and stability is the discretization in cells which are cut by the boundary, the so-called "cut-cells". In this paper, we present a new IB method, called the LS-STAG method, which is based on the MAC method for staggered Cartesian grids and where the irregular boundary is sharply represented by its level-set function. This implicit representation of the immersed boundary enables us to calculate efficiently the geometry parameters of the cut-cells. We have achieved a novel discretization of the fluxes in the cut-cells by enforcing the strict conservation of total mass, momentum and kinetic energy at the discrete level. Our discretization in the cut-cells is consistent with the MAC discretization used in Cartesian fluid cells, and has the ability to preserve the five-point Cartesian structure of the stencil, resulting in a highly computationally efficient method. The accuracy and robustness of our method is assessed on canonical flows at low to moderate Reynolds number: Taylor-Couette flow, flows past a circular cylinder, including the case where the cylinder has forced oscillatory rotations. Finally, we will extend the LS-STAG method to the handling of moving immersed boundaries and present some results for the transversely oscillating cylinder flow in a free-stream.
Differential effect of visual motion adaption upon visual cortical excitability
Lubeck, Astrid J.A.; Van Ombergen, Angelique; Ahmad, Hena; Bos, Jelte E.; Wuyts, Floris L.; Bronstein, Adolfo M.; Arshad, Qadeer
2017-01-01
The objectives of this study were 1) to probe the effects of visual motion adaptation on early visual and V5/MT cortical excitability and 2) to investigate whether changes in cortical excitability following visual motion adaptation are related to the degree of visual dependency, i.e., an
Differential effect of visual motion adaptation upon visual cortical excitability
Lubeck, A.J.A.; Ombergen, A. van; Ahmad, H.; Bos, J.E.; Wuyts, F.L.; Bronstein, A.; Arshad, Q.
2017-01-01
The objectives of this study were 1) to probe the effects of visual motion adaptation on early visual and V5/MT cortical excitability and 2) to investigate whether changes in cortical excitability following visual motion adaptation are related to the degree of visual dependency, i.e., an
Visual intelligence Microsoft tools and techniques for visualizing data
Stacey, Mark; Jorgensen, Adam
2013-01-01
Go beyond design concepts and learn to build state-of-the-art visualizations The visualization experts at Microsoft's Pragmatic Works have created a full-color, step-by-step guide to building specific types of visualizations. The book thoroughly covers the Microsoft toolset for data analysis and visualization, including Excel, and explores best practices for choosing a data visualization design, selecting tools from the Microsoft stack, and building a dynamic data visualization from start to finish. You'll examine different types of visualizations, their strengths and weaknesses, a
Prism therapy and visual rehabilitation in homonymous visual field loss.
LENUS (Irish Health Repository)
O'Neill, Evelyn C
2011-02-01
Homonymous visual field defects (HVFD) are common and frequently occur after cerebrovascular accidents. They significantly impair visual function and cause disability particularly with regard to visual exploration. The purpose of this study was to assess a novel interventional treatment of monocular prism therapy on visual functioning in patients with HVFD of varied etiology using vision targeted, health-related quality of life (QOL) questionnaires. Our secondary aim was to confirm monocular and binocular visual field expansion pre- and posttreatment.
The Elephants of Visual Literacy.
Barley, Steven D., Ed.; Ball, Richard R., Ed.
Visual literacy, as used here, refers to the skills which let a person understand and use visuals to communicate his messages and interpret the messages of others. Visual literacy should be important in the curriculum because: 1) children pay more attention to movies and television than they do to teachers; 2) the plethora of visual information…
Rodriguez, Lulu; Dimitrova, Daniela V.
2011-01-01
While framing research has centered mostly on the evaluations of media texts, visual news discourse has remained relatively unexamined. This study surveys the visual framing techniques and methods employed in previous studies and proposes a four-tiered model of identifying and analyzing visual frames: (1) visuals as denotative systems, (2) visuals…
Perception and Attention for Visualization
Haroz, Steve
2013-01-01
This work examines how a better understanding of visual perception and attention can impact visualization design. In a collection of studies, I explore how different levels of the visual system can measurably affect a variety of visualization metrics. The results show that expert preference, user performance, and even computational performance are…
Learning Science Through Visualization
Chaudhury, S. Raj
2005-01-01
In the context of an introductory physical science course for non-science majors, I have been trying to understand how scientific visualizations of natural phenomena can constructively impact student learning. I have also necessarily been concerned with the instructional and assessment approaches that need to be considered when focusing on learning science through visually rich information sources. The overall project can be broken down into three distinct segments : (i) comparing students' abilities to demonstrate proportional reasoning competency on visual and verbal tasks (ii) decoding and deconstructing visualizations of an object falling under gravity (iii) the role of directed instruction to elicit alternate, valid scientific visualizations of the structure of the solar system. Evidence of student learning was collected in multiple forms for this project - quantitative analysis of student performance on written, graded assessments (tests and quizzes); qualitative analysis of videos of student 'think aloud' sessions. The results indicate that there are significant barriers for non-science majors to succeed in mastering the content of science courses, but with informed approaches to instruction and assessment, these barriers can be overcome.
Chess Evolution Visualization.
Lu, Wei-Li; Wang, Yu-Shuen; Lin, Wen-Chieh
2014-05-01
We present a chess visualization to convey the changes in a game over successive generations. It contains a score chart, an evolution graph and a chess board, such that users can understand a game from global to local viewpoints. Unlike current graphical chess tools, which focus only on highlighting pieces that are under attack and require sequential investigation, our visualization shows potential outcomes after a piece is moved and indicates how much tactical advantage the player can have over the opponent. Users can first glance at the score chart to roughly obtain the growth and decline of advantages from both sides, and then examine the position relations and the piece placements, to know how the pieces are controlled and how the strategy works. To achieve this visualization, we compute the decision tree using artificial intelligence to analyze a game, in which each node represents a chess position and each edge connects two positions that are one-move different. We then merge nodes representing the same chess position, and shorten branches where nodes on them contain only two neighbors, in order to achieve readability. During the graph rendering, the nodes containing events such as draws, effective checks and checkmates, are highlighted because they show how a game is ended. As a result, our visualization helps players understand a chess game so that they can efficiently learn strategies and tactics. The presented results, evaluations, and the conducted user studies demonstrate the feasibility of our visualization design.
A cultura visual antes da cultura visual = Visual culture before visual culture
Directory of Open Access Journals (Sweden)
Barbosa, Anna Mae Tavares Bastos
2011-01-01
Full Text Available O artigo analisa as diferentes linhas de cultural visual que operam no ensino da arte no Brasil classificando-as como cultura visual excludente, cultura visual includente e contracultura visual. Discorre sobre teorias e abordagens aos estudos culturais e culturas visuais praticadas no Brasil desde a década de 30 citando com precursores Gilberto Freyre, Cecília Meireles, Aloísio Magalhães, Alcides da Rocha Miranda, a Escolinha de Arte de São Paulo, o Festival de Inverno de Campos do Jordão de 1983, a inter-relação da comunicação e da arte/educação na Escola de Comunicações e Artes da Universidade de São Paulo e a programação de exposições sobre a cultura visual do povo no MAC-USP nas décadas de 80 e 90
Visual Literacy in Educational Practice
Directory of Open Access Journals (Sweden)
Duchak Oksana
2014-11-01
Full Text Available In the 21stcentury the ability to interpret digital, visual and audio media is a form of literacy which is as basic as reading and writing skills. Visual literacy is required of us as much as textual literacy. Visual literacy gives educators a chance to increase the quality of their teaching and to connect with learners in more interesting way. The article elucidates the definition of visual literacy, types of visual assessment, challenges of visual literacy, and proves that visual literacy is important for learning and teaching in educational practice. Research shows that visual literacy is an essential component of science and technology education today, using visual treatments in lessons raise learning with various degrees of success. The article may encourage teachers pay their attention to visual literacy, an aspect of learning that is relatively neglected by them.
Architecture for Teraflop Visualization
Energy Technology Data Exchange (ETDEWEB)
Breckenridge, A.R.; Haynes, R.A.
1999-04-09
Sandia Laboratories' computational scientists are addressing a very important question: How do we get insight from the human combined with the computer-generated information? The answer inevitably leads to using scientific visualization. Going one technology leap further is teraflop visualization, where the computing model and interactive graphics are an integral whole to provide computing for insight. In order to implement our teraflop visualization architecture, all hardware installed or software coded will be based on open modules and dynamic extensibility principles. We will illustrate these concepts with examples in our three main research areas: (1) authoring content (the computer), (2) enhancing precision and resolution (the human), and (3) adding behaviors (the physics).
2008-12-01
Strength through structure The visualization and assessment of inner human bone structures can provide better predictions of fracture risk due to osteoporosis. Using micro-computed tomography (µCT), Christoph Räth from the Max Planck Institute for Extraterrestrial Physics and colleagues based in Munich, Vienna and Salzburg have shown how complex lattice-shaped bone structures can be visualized. The structures were quantified by calculating certain "texture measures" that yield new information about the stability of the bone. A 3D visualization showing the variation with orientation of one of the texture measures for four different bone specimens (from left to right) is shown above. Such analyses may help us to improve our understanding of disease and drug-induced changes in bone structure (C Räth et al. 2008 New J. Phys. 10 125010).
Bull, M; Evans, P J; Maclean, H
1982-05-01
Vision is the primary mode of learning and if it is absent or impaired, other pathways must be stimulated. The range of appropriate services available to visually handicapped children is explained in relation to the school run by the Royal Victorian Institution for the Blind in Melbourne. A period of residential education may be needed for children with multiple impairment. Those whose handicap is primarily visual can usually live at home and have their education integrated with that of their normal peers. Home-based services and parent support systems for preschool and kindergarten age children are outlined. To be successful, they require sharing confidential medical and education information. The school provides a major input to a discussion group of all professionals dealing with such children. Information from the group includes the causes, and educational implications of visual handicap in Victorian children. The commonest pathologies are macular problems and congenital cataract.
Visual identity and rebranding
Directory of Open Access Journals (Sweden)
Katarzyna Wrona
2015-06-01
Full Text Available The goal of this article is to highlight the essence of visual identification and rebranding, as well as to discuss elements of corporate identity, which are subject to revitalization in the process of refreshing the image of a brand. In the first part the article the analysis of the term visual identification is conducted. In the analysis special attention is drawn to the role of visual identification in creating a coherent identity of an organization. In the subsequent chapters further components of corporate identity are presented in detail – starting with logotype, through business forms, advertisements, accompanying materials and Internet websites to signs on buildings. Moreover, corporate identity book as a collection of standards and guidelines for application of corporate identity rules is discussed. The deliberations are based on the study of literature. The last chapter presented the transformation of the brand of Institute of Aviation.
Zhu, Yan
2013-01-01
A compact genome and a tiny brain make Drosophila the prime model to understand the neural substrate of behavior. The neurogenetic efforts to reveal neural circuits underlying Drosophila vision started about half a century ago, and now the field is booming with sophisticated genetic tools, rich behavioral assays, and importantly, a greater number of scientists joining from different backgrounds. This review will briefly cover the structural anatomy of the Drosophila visual system, the animal’s visual behaviors, the genes involved in assembling these circuits, the new and powerful techniques, and the challenges ahead for ultimately identifying the general principles of biological computation in the brain. A typical brain utilizes a great many compact neural circuits to collect and process information from the internal biological and external environmental worlds and generates motor commands for observable behaviors. The fruit fly Drosophila melanogaster, despite of its miniature body and tiny brain, can survive in almost any corner of the world.1 It can find food, court mate, fight rival conspecific, avoid predators, and amazingly fly without crashing into trees. Drosophila vision and its underlying neuronal machinery has been a key research model for at least half century for neurogeneticists.2 Given the efforts invested on the visual system, this animal model is likely to offer the first full understanding of how visual information is computed by a multi-cellular organism. Furthermore, research in Drosophila has revealed many genes that play crucial roles in the formation of functional brains across species. The architectural similarities between the visual systems of Drosophila and vertebrate at the molecular, cellular, and network levels suggest new principles discovered at the circuit level on the relationship between neurons and behavior in Drosophila shall also contribute greatly to our understanding of the general principles for how bigger brains work.3
Pruebas visuales en trigonometry
Directory of Open Access Journals (Sweden)
Marcelino IBAÑES JALÓN
2009-11-01
Full Text Available RESUMEN: El presente trabajo comienza explicitando lo que, en este artículo, se entiende por visualización y el aspecto que aquí interesa, que no es otro que el de ayudar a probar. A continuación, se hace referencia a algunas visualizaciones en trigonometría con esa intención y se pregunta si realmente podrían considerarse como pruebas visuales. Para responder a esta pregunta se propone averiguar la incidencia que tienen, en este tipo de visualizaciones, las funciones que se asignan a las demostraciones; con este fin se describe una experiencia realizada con alumnos de tercer curso de BUP (16-17 años, en la que se exhibieron una demostración tradicional y visualizaciones con CABRIII del Teorema de Napoleón. Se termina comentando y analizando las respuestas de los estudiantes.ABSTRACT: The present paper begins by defining «visualization» and its intended purpose, helping to illustrate a proof. We then study several visualizations used in trigonometry and ask ourselves if they may truly be considered visual proofs. In response to this question we analyze to what extent this type of visualizations contribute to the understanding of demonstrations: this is accomplished through the study of how sixteen and seventeen-year-old students (3r -year BUP responded to the traditional proof of Napoleon's Theorem and to visualizations of the same Theorem using CABRI II, followed by an analysis of the students' response to both methods.
DEFF Research Database (Denmark)
Flesch, Benjamin; Hussain, Abid; Vatrapu, Ravi
2015-01-01
application domain for the dashboard is Corporate Social Responsibility (CSR) and the targeted end-users are CSR researchers and practitioners. The design of the dashboard was based on the "social set analytics" approach to computational social science. The development of the dash-board involved cutting......This paper presents a state-of-the art visual analytics dash-board, Social Set Visualizer (SoSeVi), of approximately 90 million Facebook actions from 11 different companies that have been mentioned in the traditional media in relation to garment factory accidents in Bangladesh. The enterprise...
USGS Scientific Visualization Laboratory
,
1995-01-01
The U.S. Geological Survey's (USGS) Scientific Visualization Laboratory at the National Center in Reston, Va., provides a central facility where USGS employees can use state-of-the-art equipment for projects ranging from presentation graphics preparation to complex visual representations of scientific data. Equipment including color printers, black-and-white and color scanners, film recorders, video equipment, and DOS, Apple Macintosh, and UNIX platforms with software are available for both technical and nontechnical users. The laboratory staff provides assistance and demonstrations in the use of the hardware and software products.
Visual masking & schizophrenia
Directory of Open Access Journals (Sweden)
Michael H. Herzog
2015-06-01
Full Text Available Visual masking is a frequently used tool in schizophrenia research. Visual masking has a very high sensitivity and specificity and masking paradigms have been proven to be endophenotypes. Whereas masking is a powerful technique to study schizophrenia, the underlying mechanisms are discussed controversially. For example, for more than 25 years, masking deficits of schizophrenia patients were mainly attributed to a deficient magno-cellular system (M-system. Here, we show that there is very little evidence that masking deficits are magno-cellular deficits. We will discuss the magno-cellular and other approaches in detail and highlight their pros and cons.
Teach yourself visually laptops
Gunter, Sherry Kinkoph
2012-01-01
The fast and easy way to learn about buying, maintaining, and troubleshooting, a laptop How do I find the right laptop for me? Now that I have a laptop, how do I set it up and maintain it? What are some tips for getting the most out of software systems? How do I begin to troubleshoot my laptop? If you are a visual learner and have ever asked yourself any of those questions, then this is just the book you need. Visual, step-by-step guidance walks you through finding the right laptop to meet your needs, getting comfortable with the latest versions of Windows and the Microsoft Office Suite, and u
Visual Electricity Demonstrator
Lincoln, James
2017-09-01
The Visual Electricity Demonstrator (VED) is a linear diode array that serves as a dynamic alternative to an ammeter. A string of 48 red light-emitting diodes (LEDs) blink one after another to create the illusion of a moving current. Having the current represented visually builds an intuitive and qualitative understanding about what is happening in a circuit. In this article, I describe several activities for this device and explain how using this technology in the classroom can enhance the understanding and appreciation of physics.
Martadi
2003-01-01
At the last of twentieth century%2C the tecnology growth has changed the world display which is formed by the electronic images every where (television%2C film%2C game%2C virtual reality%2C digital photo%2C internet). The digital technology growth has brought the human fantasia throughout the limit%2C created the three dimensioan rooms with the object inside%2C until the stage of the visual reality has been passed throuhg by the visual image manipulation%2C hence%2C it is like the human being...
CMS tracker visualization tools
Energy Technology Data Exchange (ETDEWEB)
Mennea, M.S. [Dipartimento Interateneo di Fisica ' Michelangelo Merlin' e INFN sezione di Bari, Via Amendola 173 - 70126 Bari (Italy); Osborne, I. [Northeastern University, 360 Huntington Avenue, Boston, MA 02115 (United States); Regano, A. [Dipartimento Interateneo di Fisica ' Michelangelo Merlin' e INFN sezione di Bari, Via Amendola 173 - 70126 Bari (Italy); Zito, G. [Dipartimento Interateneo di Fisica ' Michelangelo Merlin' e INFN sezione di Bari, Via Amendola 173 - 70126 Bari (Italy)]. E-mail: giuseppe.zito@ba.infn.it
2005-08-21
This document will review the design considerations, implementations and performance of the CMS Tracker Visualization tools. In view of the great complexity of this sub-detector (more than 50 millions channels organized in 16540 modules each one of these being a complete detector), the standard CMS visualization tools (IGUANA and IGUANACMS) that provide basic 3D capabilities and integration within CMS framework, respectively, have been complemented with additional 2D graphics objects. Based on the experience acquired using this software to debug and understand both hardware and software during the construction phase, we propose possible future improvements to cope with online monitoring and event analysis during data taking.
Directory of Open Access Journals (Sweden)
M. Kiyasatfar
2011-01-01
Full Text Available In the present study, simulation of steady state, incompressible and fully developed laminar flow has been conducted in a magneto hydrodynamic (MHD pump. The governing equations are solved numerically by finite-difference method. The effect of the magnetic flux density and current on the flow and temperature distributions in a MHD pump is investigated. The obtained results showed that controlling the flow and the temperature is possible through the controlling of the applied current and the magnetic flux. Furthermore, the effects of the magnetic flux density and current on entropy generation in MHD pump are considered. Our presented numerical results are in good agreement with the experimental data showed in literature.
Monocular Visual Deprivation Suppresses Excitability in Adult Human Visual Cortex
DEFF Research Database (Denmark)
Lou, Astrid Rosenstand; Madsen, Kristoffer Hougaard; Paulson, Olaf Bjarne
2011-01-01
The adult visual cortex maintains a substantial potential for plasticity in response to a change in visual input. For instance, transcranial magnetic stimulation (TMS) studies have shown that binocular deprivation (BD) increases the cortical excitability for inducing phosphenes with TMS. Here, we...... employed TMS to trace plastic changes in adult visual cortex before, during, and after 48 h of monocular deprivation (MD) of the right dominant eye. In healthy adult volunteers, MD-induced changes in visual cortex excitability were probed with paired-pulse TMS applied to the left and right occipital cortex...... of visual deprivation has a substantial impact on experience-dependent plasticity of the human visual cortex....
Energy Technology Data Exchange (ETDEWEB)
Muench, M. [Freie Univ. Berlin (Germany). Fachbereich Mathematik und Informatik
2008-01-15
convergence study confirms the predicted second order accuracy of the implemented scheme. Current work in progress aims at extending the scheme presented here to the meteorologically important class anelastic, instead of incompressible, flow models. The computational code structure as presented here will transfer to these applications without change. (orig.)
1989-06-01
USAARL Report No. 89-10 0D in Visual Survey of Infantry Troops, Part I: Visual Acuity, Refractive Status, Interpupillary Distance, and Visual Skills ... librarian or other person designated to request documents from DTIC. Change of address Organizations receiving reports from the U.S. Army Aeromedical...Troops, Part I: Visual Acuity, Refractive Status, Interpupillary Distance, and Visual Skills 12. PERSONAL AUTHOR(S) David J. Walsh 13a. TYPE OF
Correlation networks visualization
Directory of Open Access Journals (Sweden)
Nicholas J. Provart
2012-10-01
Full Text Available New, in silico ways of generating hypotheses based on large data sets have emerged in the past decade. These data sets have been used to investigate different aspects of plant biology, especially at the level of transcriptome, from tissue-specific expression patterns to patterns in as little as a few cells. Such publicly-available data are a boon to researchers for hypothesis generation by providing a guide for experimental work such as phenotyping or genetic analysis. More advanced computational methods can leverage these data via gene coexpression analysis, the results of which can be visualized and refined using network analysis. Other kinds of networks of e.g. protein-protein interactions, can also be used to inform biology. These networks can be visualized and analyzed with additional information on gene expression levels, subcellular localization, etc., or with other emerging kinds information. Finally, cross-level correlation is an area that will become increasingly important. Visualizing these cross-level correlations will require new data visualization tools.
Full Text Available ... Fun Stuff Cool Eye Tricks Links to More Information Optical Illusions Printables The Visual System Ever wonder how your eyes work? Watch this video to learn how you’re able to see the world around you. Did ... on Social Media Information in Spanish (Información en español) Website, Social Media ...
IDRC Data Visualization Review
International Development Research Centre (IDRC) Digital Library (Canada)
Office 2004 Test Drive User
That said, the term data visualization can be intimidating for those less familiar with the field. This is partly because of the recent ex- plosion in dynamic and interactive data visu- alizations which have flooded the internet and media publications. While these innovative displays often create quite a splash, the key principles ...
DEFF Research Database (Denmark)
Visual Soil Evaluation (VSE) provides land users and environmental authorities with the tools to assess soil quality for crop performance. This book describes the assessment of the various structural conditions of soil, especially after quality degradation such as compaction, erosion or organic...
DEFF Research Database (Denmark)
Jakobsen, Mikkel Rønne; Hornbæk, Kasper
2011-01-01
techniques with varying display sizes (13.8, 1.5, and 0.17 megapixels). Participants navigated geographical maps to find specific locations, compare items, and follow routes. Results show that for multi-scale navigation, classic interactive visualization techniques did not benefit from being scaled...
Full Text Available ... All About Vision About the Eye Ask a Scientist Video Series Glossary The Visual System Your Eyes’ Natural Defenses Eye Health and Safety First Aid Tips Healthy Vision Tips Protective Eyewear Sports and Your Eyes Fun Stuff Cool Eye Tricks ...
DEFF Research Database (Denmark)
Flensborg, Ingelise
2009-01-01
A visual methodological approach of exploring postures and movemenets in young childrens communication with art. How do we translate bodily postures and movements into methodological categories to access data of the interactive processes? These issues will be discussed through video matrials...
DEFF Research Database (Denmark)
Fischer, Paul; Hilbert, Astrid
2012-01-01
commands, our application is select-and-click-driven. It allows to derive many different sequences of deviations for a given time series and to visualize them in different ways in order to judge their expressive power and to reuse the procedure found. For many transformations or model-ts, the user may...
DEFF Research Database (Denmark)
Jensen, Julie Borup
2017-01-01
The paper explores the potential of video ethnography concerning educational research on music as contributing to an inclusive learning environment in elementary school (research objective). In music education research, the use of visual data provided by video seems to be a relevant choice...
Seargent, David A J
2017-01-01
In these days of computers and CCD cameras, visual comet observers can still contribute scientifically useful data with the help of this handy reference for use in the field. Comets are one of the principal areas for productive pro-amateur collaboration in astronomy, but finding comets requires a different approach than the observing of more predictable targets. Principally directed toward amateur astronomers who prefer visual observing or who are interested in discovering a new comet or visually monitoring the behavior of known comets, it includes all the advice needed to thrive as a comet observer. After presenting a brief overview of the nature of comets and how we came to the modern understanding of comets, this book details the various types of observations that can usefully be carried out at the eyepiece of a telescope. Subjects range from how to search for new comets to visually estimating the brightness of comets and the length and orientation of tails, in addition to what to look for in comet heads a...
Torres Medina, Fernando
2010-01-01
Presentación del Laboratorio Virtual Visual destinado a la simulación de algoritmos de visión artificial y procesamiento de imágenes desarrollado en el Grupo de Automática, Robótica y Visión Artificial de la Universidad de Alicante.
Visualization of Traffic Accidents
Wang, Jie; Shen, Yuzhong; Khattak, Asad
2010-01-01
Traffic accidents have tremendous impact on society. Annually approximately 6.4 million vehicle accidents are reported by police in the US and nearly half of them result in catastrophic injuries. Visualizations of traffic accidents using geographic information systems (GIS) greatly facilitate handling and analysis of traffic accidents in many aspects. Environmental Systems Research Institute (ESRI), Inc. is the world leader in GIS research and development. ArcGIS, a software package developed by ESRI, has the capabilities to display events associated with a road network, such as accident locations, and pavement quality. But when event locations related to a road network are processed, the existing algorithm used by ArcGIS does not utilize all the information related to the routes of the road network and produces erroneous visualization results of event locations. This software bug causes serious problems for applications in which accurate location information is critical for emergency responses, such as traffic accidents. This paper aims to address this problem and proposes an improved method that utilizes all relevant information of traffic accidents, namely, route number, direction, and mile post, and extracts correct event locations for accurate traffic accident visualization and analysis. The proposed method generates a new shape file for traffic accidents and displays them on top of the existing road network in ArcGIS. Visualization of traffic accidents along Hampton Roads Bridge Tunnel is included to demonstrate the effectiveness of the proposed method.
Mérida Rodríguez, Matías F.
1996-01-01
El artículo intenta conceptualizar y sistematizar las principales características de una línea de estudio relativa al paisaje recientemente desarrollada, el denominado "paisaje visual", junto a ello, se analizan las causas de su aparición y desarrollo y se sintetizan sus principales metodologías.
Visual search: a retrospective.
Eckstein, Miguel P
2011-12-30
Visual search, a vital task for humans and animals, has also become a common and important tool for studying many topics central to active vision and cognition ranging from spatial vision, attention, and oculomotor control to memory, decision making, and rewards. While visual search often seems effortless to humans, trying to recreate human visual search abilities in machines has represented an incredible challenge for computer scientists and engineers. What are the brain computations that ensure successful search? This review article draws on efforts from various subfields and discusses the mechanisms and strategies the brain uses to optimize visual search: the psychophysical evidence, their neural correlates, and if unknown, possible loci of the neural computations. Mechanisms and strategies include use of knowledge about the target, distractor, background statistical properties, location probabilities, contextual cues, scene context, rewards, target prevalence, and also the role of saliency, center-surround organization of search templates, and eye movement plans. I provide overviews of classic and contemporary theories of covert attention and eye movements during search explaining their differences and similarities. To allow the reader to anchor some of the laboratory findings to real-world tasks, the article includes interviews with three expert searchers: a radiologist, a fisherman, and a satellite image analyst.
Music alters visual perception.
Jolij, Jacob; Meurs, Maaike
2011-04-21
Visual perception is not a passive process: in order to efficiently process visual input, the brain actively uses previous knowledge (e.g., memory) and expectations about what the world should look like. However, perception is not only influenced by previous knowledge. Especially the perception of emotional stimuli is influenced by the emotional state of the observer. In other words, how we perceive the world does not only depend on what we know of the world, but also by how we feel. In this study, we further investigated the relation between mood and perception. We let observers do a difficult stimulus detection task, in which they had to detect schematic happy and sad faces embedded in noise. Mood was manipulated by means of music. We found that observers were more accurate in detecting faces congruent with their mood, corroborating earlier research. However, in trials in which no actual face was presented, observers made a significant number of false alarms. The content of these false alarms, or illusory percepts, was strongly influenced by the observers' mood. As illusory percepts are believed to reflect the content of internal representations that are employed by the brain during top-down processing of visual input, we conclude that top-down modulation of visual processing is not purely predictive in nature: mood, in this case manipulated by music, may also directly alter the way we perceive the world.
Full Text Available ... System Your Eyes’ Natural Defenses Eye Health and Safety First Aid Tips Healthy Vision Tips Protective Eyewear Sports and Your Eyes Fun Stuff Cool Eye Tricks Links to More Information Optical Illusions Printables The Visual System Ever wonder how your eyes work? Watch this video to learn how you’re ...
Buddelmeijer, H.; Valentijn, E. A.; Ballester, P.; Egret, D.; Lorente, N.P.F.
The request driven way of deriving data in Astro-WISE is extended to a query driven way of visualization. This allows scientists to focus on the science they want to perform, because all administration of their data is automated. This can be done over an abstraction layer that enhances control and
Full Text Available ... Fun Stuff Cool Eye Tricks Links to More Information Optical Illusions Printables The Visual System Ever wonder how your eyes work? Watch this video to learn how you’re able to see the world around you. Did You Know? On ... on Social Media Information in Spanish (Información en español) Website, Social Media ...
Visual management support system
Lee Anderson; Jerry Mosier; Geoffrey Chandler
1979-01-01
The Visual Management Support System (VMSS) is an extension of an existing computer program called VIEWIT, which has been extensively used by the U. S. Forest Service. The capabilities of this program lie in the rapid manipulation of large amounts of data, specifically opera-ting as a tool to overlay or merge one set of data with another. VMSS was conceived to...
Visualization of hyperspectral imagery
Hogervorst, M.A.; Bijl, P.; Toet, A.
2007-01-01
We developed four new techniques to visualize hyper spectral image data for man-in-the-loop target detection. The methods respectively: (1) display the subsequent bands as a movie (movie), (2) map the data onto three channels and display these as a colour image (colour), (3) display the
Music alters visual perception.
Directory of Open Access Journals (Sweden)
Jacob Jolij
Full Text Available BACKGROUND: Visual perception is not a passive process: in order to efficiently process visual input, the brain actively uses previous knowledge (e.g., memory and expectations about what the world should look like. However, perception is not only influenced by previous knowledge. Especially the perception of emotional stimuli is influenced by the emotional state of the observer. In other words, how we perceive the world does not only depend on what we know of the world, but also by how we feel. In this study, we further investigated the relation between mood and perception. METHODS AND FINDINGS: We let observers do a difficult stimulus detection task, in which they had to detect schematic happy and sad faces embedded in noise. Mood was manipulated by means of music. We found that observers were more accurate in detecting faces congruent with their mood, corroborating earlier research. However, in trials in which no actual face was presented, observers made a significant number of false alarms. The content of these false alarms, or illusory percepts, was strongly influenced by the observers' mood. CONCLUSIONS: As illusory percepts are believed to reflect the content of internal representations that are employed by the brain during top-down processing of visual input, we conclude that top-down modulation of visual processing is not purely predictive in nature: mood, in this case manipulated by music, may also directly alter the way we perceive the world.
Full Text Available ... National Eye Institute’s mission is to “conduct and support research, training, health information dissemination, and other programs ... search for current job openings visit HHS USAJobs Home > NEI for Kids > The Visual System All About ...
Standardizing visual display quality
Besuijen, J.; Spenkelink, G.P.J.
1998-01-01
The current ISO 9241–3 standard for visual display quality and the proposed user performance tests are reviewed. The standard is found to be more engineering than ergonomic and problems with system configuration, software applications, display settings, user behaviour, wear and physical environment
Visual Information Communications International Conference
Nguyen, Quang Vinh; Zhang, Kang; VINCI'09
2010-01-01
Visual Information Communication is based on VINCI'09, The Visual Information Communications International Conference, September 2009 in Sydney, Australia. Topics covered include The Arts of Visual Layout, Presentation & Exploration, The Design of Visual Attributes, Symbols & Languages, Methods for Visual Analytics and Knowledge Discovery, Systems, Interfaces and Applications of Visualization, Methods for Multimedia Data Recognition & Processing. This cutting-edge book addresses the issues of knowledge discovery, end-user programming, modeling, rapid systems prototyping, education, and design activities. Visual Information Communications is an edited volume whose contributors include well-established researchers worldwide, from diverse disciplines including architects, artists, engineers, and scientists. Visual Information Communication is designed for a professional audience composed of practitioners and researchers working in the field of digital design and visual communications. This volume i...
Visual cognition in social insects.
Avarguès-Weber, Aurore; Deisig, Nina; Giurfa, Martin
2011-01-01
Visual learning admits different levels of complexity, from the formation of a simple associative link between a visual stimulus and its outcome, to more sophisticated performances, such as object categorization or rules learning, that allow flexible responses beyond simple forms of learning. Not surprisingly, higher-order forms of visual learning have been studied primarily in vertebrates with larger brains, while simple visual learning has been the focus in animals with small brains such as insects. This dichotomy has recently changed as studies on visual learning in social insects have shown that these animals can master extremely sophisticated tasks. Here we review a spectrum of visual learning forms in social insects, from color and pattern learning, visual attention, and top-down image recognition, to interindividual recognition, conditional discrimination, category learning, and rule extraction. We analyze the necessity and sufficiency of simple associations to account for complex visual learning in Hymenoptera and discuss possible neural mechanisms underlying these visual performances.
Visual deficits in anisometropia.
Levi, Dennis M; McKee, Suzanne P; Movshon, J Anthony
2011-01-01
Amblyopia is usually associated with the presence of anisometropia, strabismus or both early in life. We set out to explore quantitative relationships between the degree of anisometropia and the loss of visual function, and to examine how the presence of strabismus affects visual function in observers with anisometropia. We measured optotype acuity, Pelli-Robson contrast sensitivity and stereoacuity in 84 persons with anisometropia and compared their results with those of 27 persons with high bilateral refractive error (isoametropia) and 101 persons with both strabismus and anisometropia. All subjects participated in a large-scale study of amblyopia (McKee et al., 2003). We found no consistent visual abnormalities in the strong eye, and therefore report only on vision in the weaker, defined as the eye with lower acuity. LogMAR acuity falls off markedly with increasing anisometropia in non-strabismic anisometropes, while contrast sensitivity is much less affected. Acuity degrades rapidly with increases in both hyperopic and myopic anisometropia, but the risk of amblyopia is about twice as great in hyperopic than myopic anisometropes of comparable refractive imbalance. For a given degree of refractive imbalance, strabismic anisometropes perform considerably worse than anisometropes without strabismus--visual acuity for strabismics was on average 2.5 times worse than for non-strabismics with similar anisometropia. For observers with equal refractive error in the two eyes there is very little change in acuity or sensitivity with increasing (bilateral) refractive error except for one extreme individual (bilaterally refractive error of -15 D). Most pure anisometropes with interocular differences less than 4D retain some stereopsis, and the degree is correlated with the acuity of the weak eye. We conclude that even modest interocular differences in refractive error can influence visual function. Copyright © 2010 Elsevier Ltd. All rights reserved.
Directory of Open Access Journals (Sweden)
Martadi
2003-01-01
Full Text Available At the last of twentieth century%2C the tecnology growth has changed the world display which is formed by the electronic images every where (television%2C film%2C game%2C virtual reality%2C digital photo%2C internet. The digital technology growth has brought the human fantasia throughout the limit%2C created the three dimensioan rooms with the object inside%2C until the stage of the visual reality has been passed throuhg by the visual image manipulation%2C hence%2C it is like the human being step from the real to the fantastic world%2C an imagination which seems like the truth. The problem becomes more complex when we have to face the reality that the technology growth brings the negative impacts. While the tecnology could be satisfy the human desire%2C giving an esctasy fantasia%2C then the moral values is nullified one by one. Criminals%2C pornography%2C come up freely wear the newest formats. Abstract in Bahasa Indonesia : Perkembangan teknologi pada akhir abad ke-20 telah merubah wajah dunia yang dibentuk oleh riuh rendah citraan elektronik (televisi%2C film%2C game%2C virtual reality%2C foto digital%2C internet. Perkembangan teknologi digital telah membawa fantasi manusia menembus batas%2C menciptakan ruang-ruang tiga dimensi berikut obyek-obyek di dalamnya%2C sampai pada tahap di mana realitas visual telah dilampaui dengan manipulasi pencitraan visual%2C sehingga seolah manusia melangkah dari dunia nyata menuju dunia fantasi%2C dunia maya yang tampak nyata. Permasalahannya menjadi semakin rumit ketika kita dihadapkan pada realita bahwa perkembangan teknologi tersebut membawa pula dampak negatif. Pada saat teknologi memuaskan hasrat/nafsu manusia%2C memberikan pesona ekstasi%2C maka nilai-nilai moral seakan rontok satu per satu. Hyper-reality%2C Visual.
Reflexive Learning through Visual Methods
DEFF Research Database (Denmark)
Frølunde, Lisbeth
2014-01-01
What. This chapter concerns how visual methods and visual materials can support visually oriented, collaborative, and creative learning processes in education. The focus is on facilitation (guiding, teaching) with visual methods in learning processes that are designerly or involve design. Visual...... methods are exemplified through two university classroom cases about collaborative idea generation processes. The visual methods and materials in the cases are photo elicitation using photo cards, and modeling with LEGO Serious Play sets. Why. The goal is to encourage the reader, whether student...
Reflective Reconstruction of Visual Products
DEFF Research Database (Denmark)
Otrel-Cass, Kathrin
2017-01-01
of visuals. A case of a New Zealand year 7/8 primary science class studying the water cycle is presented. It is argued that teaching science concepts like the water cycle through visualizations cannot be an abstract endeavor because even when abstract ideas are presented, they are visualized as concrete......This paper presents an argument about the cultural construction of visual products. Based on data from video observations, interviews and the collection of student-produced (visual) artifacts, a material ethnography approach is presented. Applying reflexivity with the use of visuals, the following...
Customizable Time-Oriented Visualizations
DEFF Research Database (Denmark)
Kuhail, Mohammad Amin; Pantazos, Kostas; Lauesen, Søren
2012-01-01
Most commercial visualization tools support an easy and quick creation of conventional time-oriented visualizations such as line charts, but customization is limited. In contrast, some academic visualization tools and programming languages support the creation of some customizable time-oriented v......Most commercial visualization tools support an easy and quick creation of conventional time-oriented visualizations such as line charts, but customization is limited. In contrast, some academic visualization tools and programming languages support the creation of some customizable time...
The Pitfalls of Visual Representations
Directory of Open Access Journals (Sweden)
Sabrina Bresciani
2015-10-01
Full Text Available A large body of research has addressed the benefits of visualization, whereas the analysis of the pitfalls has not received systematic attention. We aim to provide an overview of the common pitfalls and potential disadvantages of visual representations based on a multidisciplinary literature review. Subsequently, we develop a theoretically grounded classification of common cognitive, emotional, and social risks of visualization and populate it with a comprehensive list of visualization pitfalls. The aim of this research is not to diminish the potential of visualization, but rather to improve visual literacy by structuring our understanding of the possible limitations of graphic representations.
Data visualization a guide to visual storytelling for libraries
2016-01-01
Data Visualization: A Guide to Visual Storytelling for Libraries is a practical guide to the skills and tools needed to create beautiful and meaningful visual stories through data visualization. Learn how to sift through complex datasets to better understand a variety of metrics, such as trends in user behavior and electronic resource usage, return on investment (ROI) and impact metrics, and learning and reference analytics. Sections include: .Identifying and interpreting datasets for visualization .Tools and technologies for creating meaningful visualizations .Case studies in data visualization and dashboards Understanding and communicating trends from your organization s data is essential. Whether you are looking to make more informed decisions by visualizing organizational data, or to tell the story of your library s impact on your community, this book will give you the tools to make it happen."
Poke and pop : Tactile-visual synchrony increases visual saliency
Burg, E. van der; Olivers, C.N.L.; Bronkhorst, A.W.; Theeuwes, J.
2009-01-01
The majority of studies investigating interactions between vision and touch have typically explored single events, presenting one object at a time. The present study investigates how tactile-visual interactions affect competition between multiple visual objects in more dynamic cluttered
Assessment of visual disability using visual evoked potentials.
Jeon, Jihoon; Oh, Seiyul; Kyung, Sungeun
2012-08-06
The purpose of this study is to validate the use of visual evoked potential (VEP) to objectively quantify visual acuity in normal and amblyopic patients, and determine if it is possible to predict visual acuity in disability assessment to register visual pathway lesions. A retrospective chart review was conducted of patients diagnosed with normal vision, unilateral amblyopia, optic neuritis, and visual disability who visited the university medical center for registration from March 2007 to October 2009. The study included 20 normal subjects (20 right eyes: 10 females, 10 males, ages 9-42 years), 18 unilateral amblyopic patients (18 amblyopic eyes, ages 19-36 years), 19 optic neuritis patients (19 eyes: ages 9-71 years), and 10 patients with visual disability having visual pathway lesions. Amplitude and latencies were analyzed and correlations with visual acuity (logMAR) were derived from 20 normal and 18 amblyopic subjects. Correlation of VEP amplitude and visual acuity (logMAR) of 19 optic neuritis patients confirmed relationships between visual acuity and amplitude. We calculated the objective visual acuity (logMAR) of 16 eyes from 10 patients to diagnose the presence or absence of visual disability using relations derived from 20 normal and 18 amblyopic eyes. Linear regression analyses between amplitude of pattern visual evoked potentials and visual acuity (logMAR) of 38 eyes from normal (right eyes) and amblyopic (amblyopic eyes) subjects were significant [y = -0.072x + 1.22, x: VEP amplitude, y: visual acuity (logMAR)]. There were no significant differences between visual acuity prediction values, which substituted amplitude values of 19 eyes with optic neuritis into function. We calculated the objective visual acuity of 16 eyes of 10 patients to diagnose the presence or absence of visual disability using relations of y = -0.072x + 1.22 (-0.072). This resulted in a prediction reference of visual acuity associated with malingering vs. real
Assessment of visual disability using visual evoked potentials
Directory of Open Access Journals (Sweden)
Jeon Jihoon
2012-08-01
Full Text Available Abstract Background The purpose of this study is to validate the use of visual evoked potential (VEP to objectively quantify visual acuity in normal and amblyopic patients, and determine if it is possible to predict visual acuity in disability assessment to register visual pathway lesions. Methods A retrospective chart review was conducted of patients diagnosed with normal vision, unilateral amblyopia, optic neuritis, and visual disability who visited the university medical center for registration from March 2007 to October 2009. The study included 20 normal subjects (20 right eyes: 10 females, 10 males, ages 9–42 years, 18 unilateral amblyopic patients (18 amblyopic eyes, ages 19–36 years, 19 optic neuritis patients (19 eyes: ages 9–71 years, and 10 patients with visual disability having visual pathway lesions. Amplitude and latencies were analyzed and correlations with visual acuity (logMAR were derived from 20 normal and 18 amblyopic subjects. Correlation of VEP amplitude and visual acuity (logMAR of 19 optic neuritis patients confirmed relationships between visual acuity and amplitude. We calculated the objective visual acuity (logMAR of 16 eyes from 10 patients to diagnose the presence or absence of visual disability using relations derived from 20 normal and 18 amblyopic eyes. Results Linear regression analyses between amplitude of pattern visual evoked potentials and visual acuity (logMAR of 38 eyes from normal (right eyes and amblyopic (amblyopic eyes subjects were significant [y = −0.072x + 1.22, x: VEP amplitude, y: visual acuity (logMAR]. There were no significant differences between visual acuity prediction values, which substituted amplitude values of 19 eyes with optic neuritis into function. We calculated the objective visual acuity of 16 eyes of 10 patients to diagnose the presence or absence of visual disability using relations of y = −0.072x + 1.22 (−0.072. This resulted in a prediction
Visual Information Presentation in Continuous Control Systems using Visual Enhancements
Park, Jaekyu; Park, Sung Ha
2008-01-01
This chapter was intended to identify and quantify the effects of visual enhancement cues on the performance of continuous control tasks such as tracking tasks. Also, we investigated the types and utilities of visual enhancements as visual aids that improve a performance and offer spatial information. Especially, we have indentified that various visual enhancements improve not only a performance but also the possibility of an error through a case study. The findings of this chapter are applic...
From visual performance to visual ergonomics: A personal historic view
Vos, J.J.
2009-01-01
During the author's active time in vision research a change in attitude took place from 'visual performance' as a criterion to justify higher light levels, to 'visual ergonomics' as a more comprehensive approach to improve visual work conditions. Some personal memories of this transition period may
Irrelevant Auditory and Visual Events Induce a Visual Attentional Blink
Van der Burg, Erik; Nieuwenstein, Mark R.; Theeuwes, Jan; Olivers, Christian N. L.
2013-01-01
In the present study we investigated whether a task-irrelevant distractor can induce a visual attentional blink pattern. Participants were asked to detect only a visual target letter (A, B, or C) and to ignore the preceding auditory, visual, or audiovisual distractor. An attentional blink was
Perceptual Dependencies in Information Visualization Assessed by Complex Visual Search
Berg, Ronald van den; Cornelissen, Frans W.; Roerdink, Jos B.T.M.
A common approach for visualizing data sets is to map them to images in which distinct data dimensions are mapped to distinct visual features, such as color, size and orientation. Here, we consider visualizations in which different data dimensions should receive equal weight and attention. Many of
Directory of Open Access Journals (Sweden)
Skrzypulec Błażej
2015-06-01
Full Text Available While it is widely accepted that human vision represents objects, it is less clear which of the various philosophical notions of ‘object’ adequately characterizes visual objects. In this paper, I show that within contemporary cognitive psychology visual objects are characterized in two distinct, incompatible ways. On the one hand, models of visual organization describe visual objects in terms of combinations of features, in accordance with the philosophical bundle theories of objects. However, models of visual persistence apply a notion of visual objects that is more similar to that endorsed in philosophical substratum theories. Here I discuss arguments that might show either that only one of the above notions of visual objects is adequate in the context of human vision, or that the category of visual objects is not uniform and contains entities properly characterized by different philosophical conceptions.
Effective Presentations with Visual Aids
Rascon, Brian
2017-01-01
Las presentaciones efectivas incluyen a menudo ayudas visuales. En este documento se describe lo que se puede y lo que no se puede hacer para diversos tipos de ayudas visuales, principalmente para las presentaciones asistidas por Powerpoint.
Bianchi, R. M.; Boudreau, J.; Konstantinidis, N.; Martyniuk, A. C.; Moyse, E.; Thomas, J.; Waugh, B. M.; Yallup, D. P.; ATLAS Collaboration
2017-10-01
At the beginning, HEP experiments made use of photographical images both to record and store experimental data and to illustrate their findings. Then the experiments evolved and needed to find ways to visualize their data. With the availability of computer graphics, software packages to display event data and the detector geometry started to be developed. Here, an overview of the usage of event display tools in HEP is presented. Then the case of the ATLAS experiment is considered in more detail and two widely used event display packages are presented, Atlantis and VP1, focusing on the software technologies they employ, as well as their strengths, differences and their usage in the experiment: from physics analysis to detector development, and from online monitoring to outreach and communication. Towards the end, the other ATLAS visualization tools will be briefly presented as well. Future development plans and improvements in the ATLAS event display packages will also be discussed.
AUTHOR|(INSPIRE)INSPIRE-00211497; The ATLAS collaboration; Boudreau, Joseph; Konstantinidis, Nikolaos; Martyniuk, Alex; Moyse, Edward; Thomas, Juergen; Waugh, Ben; Yallup, David
2017-01-01
At the beginning, HEP experiments made use of photographical images both to record and store experimental data and to illustrate their findings. Then the experiments evolved and needed to find ways to visualize their data. With the availability of computer graphics, software packages to display event data and the detector geometry started to be developed. Here, an overview of the usage of event display tools in HEP is presented. Then the case of the ATLAS experiment is considered in more detail and two widely used event display packages are presented, Atlantis and VP1, focusing on the software technologies they employ, as well as their strengths, differences and their usage in the experiment: from physics analysis to detector development, and from online monitoring to outreach and communication. Towards the end, the other ATLAS visualization tools will be briefly presented as well. Future development plans and improvements in the ATLAS event display packages will also be discussed.
Visualizations as Projection Devices
DEFF Research Database (Denmark)
Harty, Chris; Holm Jacobsen, Peter; Tryggestad, Kjell
connected to create projections of a future perfect, yet integral to this process a number of concerns emerges in the processes of designing and constructing the new hospital. These emergent concerns, in turn, have practical implications for the management of complex hospital construction projects......The aim of this paper is to inquire into the role of project visualizations in shaping healthcare spaces and practices. The study draws upon an ethnographic field study from a large on-going hospital construction project in Denmark, and focuses on the early phases of on-boarding the design team...... schedule for the hospital construction project. The study reveals how the visualizations are dynamically developed and linked to each other and their role in facilitating both control and innovation in project work and clinical work at the hospital. The paper contributes to our understanding of the active...
Advanced Visual Quantum Mechanics
Thaller, Bernd
2005-01-01
Advanced Visual Quantum Mechanics is a systematic effort to investigate and to teach quantum mechanics with the aid of computer-generated animations. It is a self-contained textbook that combines selected topics from atomic physics (spherical symmetry, the hydrogen atom, and particles with spin) with an introduction to quantum information theory (qubits, EPR paradox, teleportation, quantum computers). It explores relativistic quantum mechanics and the strange behavior of Dirac equation solutions. A series of appendices covers important topics from perturbation and scattering theory. The book places an emphasis on ideas and concepts, with a fair to moderate amount of mathematical rigor. Though this book stands alone, it can also be paired with Thaller Visual Quantum Mechanics to form a comprehensive course in quantum mechanics. The software for the first book earned the European Academic Software Award 2000 for outstanding innovation in its field.
Directory of Open Access Journals (Sweden)
Elaine de Azevedo
2016-12-01
Full Text Available This theoretical-conceptual study highlights issues and debates related to food under a socio-political and cultural perspective, from different audiovisual media - cinema, TV, reality shows and Internet videos. The article focuses particularly on movies that mobilize the food as a transversal axis of the plots. The idea is to complexify food as a visual theme and as a sensorial strategy.
Sippola, Juha
2013-01-01
The idea for this Bachelor’s thesis came from Digia, which develops Qt, a cross-platform application and UI framework for software developers, together with the Qt Project, a meritocratic consensus-based open source developer community. The main objective of this thesis was to improve the visualization and communication of the Qt quality by creating a web portal to collect and display metrics on required Qt process areas, focusing on continuous integration. Raw results are available from many...
Science information systems: Visualization
Wall, Ray J.
1991-01-01
Future programs in earth science, planetary science, and astrophysics will involve complex instruments that produce data at unprecedented rates and volumes. Current methods for data display, exploration, and discovery are inadequate. Visualization technology offers a means for the user to comprehend, explore, and examine complex data sets. The goal of this program is to increase the effectiveness and efficiency of scientists in extracting scientific information from large volumes of instrument data.
Network Security Visualization
1999-09-27
Internet Scanner 5.2 User Guide for Windows NT”, Internet Security Systems, Inc., 1998. “SBIR Topic AF97-043 Network Security Visualization...to the Server application to import into the NSV system database data that gets queried from ISS Internet Security Scanner 5.4. Objective #5 was... Internet Security Scanner scan of a live network and imported through a Cartridge component. The data was accessed through the Server component and