Send mail to: mgnet@cs.yale.edu for the digests or bakeoff mgnet-requests@cs.yale.edu for comments or help Current editor: Craig Douglas douglas-craig@cs.yale.edu Anonymous ftp repository: ftp.ccs.uky.edu (128.163.209.106) World Wide Web: http://www.mgnet.org or http://casper.cs.yale.edu/mgnet/www/mgnet.html or http://www.cerfacs.fr/~douglas/mgnet.html or http://phase.etl.go.jp/mgnet or http://www.nchc.gov.tw/RESEARCH/Math/mgnet/www/mgnet.html Today's editor: Craig Douglas (douglas-craig@cs.yale.edu) Volume 9, Number 6 (approximately June 30, 1999) Today's topics: A Call for Help Two Papers (Brandt) Copper Mountain Contribution (Paraschivoiu and Cai) Copper Tutorial: Parallel Multigrid Copper Tutorial: Algebraic Multigrid Copper Transparencies (Johannsen) Summer School on CFD EMG99: Final Announcement ------------------------------------------------------- Date: Fri, 18 Jun 1999 17:00:26 -0400 (EDT) From: Dejan VinkovicSubject: A Call for Help Dear Sirs/Madams, I am a PhD student at Dept. of Phys. and Astro., Univ. of Kentucky. I'm currently working on the code for 2D radiative transfer in dust around stars. I would be very thankful if somebody can help me with problems related to the grid generation. Any suggestion, comment, advice or reference about the grid generation with described properties (see below) would be very helpful. Also, suggestions and comments about methods for solving the radiative transfer equation (or integro-differential equations in general) are appreciated. More extensive description of the problem (4 pages, with equations) is available here: http://www.pa.uky.edu/~dejan/work/2D-grid.ps Thank you very much. Dejan Vinkovic University of Kentucky Department of Physics and Astronomy 177 Chem-Phys Bldg Lexington KY 40506 E-mail: dejan@pa.uky.edu 2D Radiative Transfer in Dusty Stellar Environments The dust configuration around stars usually has rotational symmetry. It can absorb, scatter and re-emit the radiation from the star, that is, change the stellar spectral continuum. To solve the integro-differential radiation transfer equation in the dusty circumstellar cloud, we need the temperature distribution at all points in the cloud. But the temperature is determined from the local energy density, obtained from the transfer equation. Thus the emerging spectrum is calculated by iterations between calculated temperature in one step, and energy density in another. The dust consists of several different chemical components, each one with different sublimation temperature, above which specific type of dust can not exist. Thus the dust density has discontinuities at the points with sublimation temperatures. Moreover, we don't know exact position of these points because we don't know a priori the correct temperature distribution. Obviously, the most important part of the calculation process is generation of the computational grid. A grid generator has to be applied after each temperature iteration because the sublimation surface will be changed. Thus we can impose some demands on the grid generator: - it has to follow the density gradient, with discontinuities - it has to be fast and applied several times during the calculation (or somehow move the grid points at sublimation surface toward new position after the temperature is updated) There is a concern that the discrete ordinate method, usually applied in the radiative heat transfer, would not be able to recognize possible abrupt changes in intensities during the angular integration. Therefore, some other method could be more appropriate after the grid generation. ------------------------------------------------------- Date: Thu, 20 May 99 09:00:13 +0300 From: "Prof. Achi Brandt" Subject: Two Papers My secretary Sarah will be sending you for MGNET the paper I have for the Copper Proceedings. General Highly Accurate Algebraic Coarsening Schemes Editor's Note: See http://www.mgnet.org/mgnet-ccmm99.html or access it at ------------- http://www.mgnet.org/mgnet/Conferences/CopperMtn99/Papers/brandt.ps.gz I also have a new summary paper, extending by much my 1997 Copper paper. It appears in my homepage at www.wisdom.weizmann.ac.il/~achi Multiscale Scientific Computation: Six Year Research Summary Achi Brandt The Weizmann Institute of Science Rehovot, 76100, Israel Abstract The Gauss Center research on multiscale computational methods is reported, emphasizing main ideas and inter-relations between various fields, and listing the relevant bibliography. The reported areas include: top-efflciency multigrid methods in fluid dynamics; atmospheric flows and data assimilation; feedback optimal control; PDE solvers on unbounded domains; wave/ray methods for highly indefinite equations; rigorous quantitative analysis of multigrid; many-eigenfunction problems and ab-initio quantum chemistry; fast evaluation of integral transforms on adaptive grids; multigrid Dirac solvers; fast inverse-matrix and determinant updates;multiscale Monte-Carlo methods in statistical physics; molecular mechanics (including fast force summation, fast macromolecular energy minimization, Monte-Carlo methods at equilibrium, both for macromolecules and for large ensembles of small molecules, and the combination of small-scale equilibrium with large-scale dynamics); image processing (edge detection and segmentation); and tomography (medical imaging and radar reconstruction). Key words. Scientific computation, multiscale, multi-resolution, multigrid, fluid dynamics, atmospheric flows, data assimilation, optimal control, wave problems, Dirac equations, inverse matrix, Schrodinger operator, Monte-Carlo algorithms, critical slowing down, molecular mechanics, fast force summation, energy minimization, integro-differential equations, tomography , medical imaging, radar, image processing, edge detection, segmentation, algebraic multigrid. AMS subject classification. 34A50, 35A40, 44-04, 45{04, 65C05, 65F10, 65F15, 65F40, 65K10, 65M30, 65M50, 65M55, 65N22, 65N25, 65N38, 65N55, 65R10, 65R20, 65Y05, 68U10, 70-08, 76-04, 76M20, 81-08, 81T80, 82-08, 82B80, 82C80, 92E99 Editor's Note: See http://www.mgnet.org/mgnet-papers.html or access it at ------------- http://www.mgnet.org/mgnet/papers/Brandt/review99.ps.gz ------------------------------------------------------- Date: Tue, 22 Jun 1999 14:33:22 -0600 From: Marius Paraschivoiu Subject: Copper Mountain Contribution (Paraschivoiu and Cai) A Unigrid Multi-Model Full Potential and Euler Formulation for Transonic Flows Marius Paraschivoiu Department of Mechanical and Industrial Engineering University Toronto Toronto, Canada M5S 3G8 Xiao-Chuan Cai Department of Computer Science University of Colorado Boulder, CO 80309, USA Abstract In this paper we present a unigrid multi-model formulation for transonic flow calculations based on solving, in sequence, the full potential equation and the the Euler equations. The goal is to minimize the overall computation time to simulate steady flows by using a more computational efficient physical model in the early iteration steps. The proposed method is based on two steps. In the first step, the full potential equation is solved to obtain a intermediate solution which is ``improved'', in the second step, by solving the Euler equations. The full potential equation and the Euler equations are discretized on the same unstructured mesh to avoid new coarse grid generation and to simplify the transfer, between the two models. The resulting nonlinear systems are solved by a Newton-Krylov algorithm. To demonstrate the feasibility of this multi-model formulation, we present computational results for a three-dimensional transonic flows around a nonlifting wing created from a NACA0012 airfoil. Editor's Note: See http://www.mgnet.org/mgnet-ccmm99.html or access it at ------------- http://www.mgnet.org/mgnet/Conferences/CopperMtn99/Papers/paraschivoiu.ps.gz ------------------------------------------------------- Date: Thu, 24 Jun 1999 17:42:26 -0700 (PDT) From: "Jim E. Jones" Subject: Copper Tutorial: Parallel Multigrid I've put the slides for my Copper tutorial on MGNet. This presentation focuses on the issues involved in parallelizing a multigrid algorithm. Assuming no experience with parallel computing, but an understanding of the principles of multigrid, the tutorial introduces some of the standard and efficient techniques for developing a parallel multigrid solver. Contents * Algorithmic and implementation scalability. * Parallelization of multigrid by domain partitioning. * Performance models and metrics for parallel multigrid solvers. * Novel parallel multigrid algorithms: multiple coarse grids and concurrent multigrid. Editor's Note: See http://www.mgnet.org/mgnet-ccmm99.html or ------------- http://www.mgnet.org/mgnet-tuts.html or access it at http://www.mgnet.org/mgnet/Conferences/CopperMtn99/Tutorials/parallel.ps.gz ------------------------------------------------------- Date: Thu, 24 Jun 1999 09:10:32 -0700 (PDT) From: Van Henson Subject Copper Tutorial: Algebraic Multigrid Here are the cleared slides for my tutorial. They are in Powerpoint and you can figure out how to make them into an html document. This introduction focuses primarily on the "classical" AMG of Brandt, McCormick, and Ruge. An understanding of the principles of multigrid is assumed, but the tutorial introduces algebraic multigrid in a simple, practical manner. Contents * "Classical" AMG o Hammers and Wrenches: the Required AMG Toolkit o The Ardent Quest: Seeking Algebraic Smoothness o Get to the Point: Coarse Grid Selection o Building a Better Mousetrap: Prolongation * Other Algebraic Approaches: an Overview o Smoothed Aggregation o Multigraph methods o AMGe o Energy-Minimizing Basis methods Editor's Note: See http://www.mgnet.org/mgnet-ccmm99.html or ------------- http://www.mgnet.org/mgnet-tuts.html or access it at http://www.mgnet.org/mgnet/Conferences/CopperMtn99/Tutorials/amgtut_clrd.ppt.gz I am still trying to get the html version to work... Van Emden Henson | "All intelligent conversation is Center for Applied Scientific Computing | playing on words. The rest is Lawrence Livermore National Laboratory | definition and instruction." PO Box 808 L-560 | - Herman Wouk Livermore, CA 94551 | | vhenson@llnl.gov | Phone: (925) 423-4283 http://www.llnl.gov/CASC/people/henson | Fax: (925) 422-6287 ------------------------------------------------------- Date: Sun, 30 May 1999 12:07:03 +0200 From: klaus Subject: Summer School on CFD EMS-WiR Summer School on Numerical Simulation of Flows Heidelberg September 6-21, 1999 G. Wittum, Heidelberg The numerical simulation of flows is one of the central problems in Scientific Computing. Complexity of flow simulations is so high that a realistic description requires sophisticated mathematical methods and models. In particular modeling and simulation of turbulent flows, nearly incompressible flows, and multi-phase flows are challenging problems for mathematical models and numerical methods. There is a strong interest in this topic by numerous groups from mathematical modelling and numerical simulation. Recently a number of new mathematical models and methods have been introduced which are highly relevant for flow simulations. Amongst others these are multiscale modelling and numerics, homogenization, finite-element and finite volume methods, spectral and h-p discretizations, grid adaptivity and error estimators, multigrid and conjugate-gradient type methods and wavelets. Another field of increasing importance is the development of methods for the visualization of flows. The numerical simulation of flows requires cooperation of several mathematical disciplines as Analysis, Numerics, Mathematical Physics and Computational Science. The European Mathematical Society (EMS) together with the research network WiR will organize a summer school on Numerical Simulation of Flows from Sept. 6 - 21, 1999 in Heidelberg. The summer school is a joint event with AMIF (Applied Mathematics for Industrial Flow Problems) and SFB 359 of Heidelberg University. The Summer school will consist of a theoretical and a practical part, each one lasting a week. The first week (Sept. 6-10, in Heidelberg) is devoted to basic instruction. During this week mathematical models and methods are presented in lectures given by specialists. In the second week (Sept. 13-17) the participants will work on problems posed by the lecturers in different places (Heidelberg, Freiburg, Stuttgart, Zurich). Finally the results of this work will be presented in a plenary meeting (Sept. 20-21, in Heidelberg). Scientific Comittee: P. Bastian, Heidelberg, G. Dziuk, Freiburg, W. Hackbusch, Leipzig, R. Jeltsch, Zurich, D. Krner, Freiburg, C.-D. Munz, Stuttgart, R. Rannacher, Heidelberg, W. Rodi, Karlsruhe, S. Sauter, Leipzig S. Wagner, Stuttgart, G. Wittum, Heidelberg, H. Yserentant, Tubingen Local Organizer: G. Wittum, Technische Simulation, IWR, Universitat Heidelberg, Im Neuenheimer Feld 368, D-69120 Heidelberg, email: ems@iwr.uni-heidelberg.de, http://www.iwr.uni-heidelberg.de/~techsim/summerschool Registration: Online via http://www.iwr.uni-heidelberg.de/~techsim/summerschool Registration fee: DM 300,? payed until July 15th, DM 400,? later. The fee covers participation, lunches, coffee breaks, and materials. All payments, net of all charges, are to be made in Deutsche Mark by bank transfer to account No. 50 302 787 600, Baden-Wuerttembergische-Bank Heidelberg, BLZ 672 700 20, with the address: Universitaet Heidelberg, EMS, Kap 1412/TG86/BA1103. Registration deadline: July 15th 1999. Lodging reservation: Please book rooms for the first week in Heidelberg as early as possible using http://www.heidelberg.de/verkehrsverein/deutsch/hotels_index.htm for booking rooms for the first week in Heidelberg. A limited number of cheap rooms is availble for the first week in Heidelberg (see registration form). Financial support of participation: A limited number of scholarships by EMS is available. To apply for such a scholarship, please add a short curriculum vitae, a sketch of your research interests and a letter of recommendation. Prof. Dr. Gabriel Wittum tel/fax: +49 6221 54 8860 tel/work: +49 6221 54 8855 url: http://www.iwr.uni-heidelberg.de/~techsim org: Technische Simulation, IWR, Universitaet Heidelberg adr: Im Neuenheimer Feld 368, D-69120 Heidelberg, Germany email: wittum@iwr.uni-heidelberg.de ------------------------------------------------------- Date: Wed, 30 Jun 1999 17:48:14 +0200 From: Erik Dick Subject: EMG99: Final Announcement Final announcement Sixth European Multigrid Conference Universiteit Gent, Belgium September 27 - 30, 1999 A preliminary program of the conference is now available. 54 papers have been selected for presentation. For information and registration please consult our website at http://allserv.rug.ac.be/~edick/emg (press reload if necessary). ------------------------------ End of MGNet Digest **************************