Welcome to

CTAC2004

 

The 12th Biennial Computational Techniques and Applications Conference

27 September - 1 October 2004

The University of Melbourne
Victoria Australia

Invited Speakers

Prof. Gary Leal

Prof. Mark Cross

Dr Robert Anderssen

Prof. Chaoqun Liu

Prof. Denis Evans

Dr Paul MacKerras

Workshops

Invited Speakers

Prof. Gary Leal
Department of Chemical Engineering University of California at Santa Barbara, USA

Computational Studies in Materials Research

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Prof. Mark Cross
Centre for Numerical Modelling and Process Analysis University of Greenwich London, UK

A perspective on the current status of the challenges in the computational modelling of fluids interacting with other physical phenomena

Abstract
These days the computational modelling of fluids is increasingly accompanied by the need to include its interactions with other phenomena, such as, electromagnetic fields and structural responses. In this sense, the modelling of this class of processes is best characterised as 'multi-physics', where although CFD is at the heart of the simulation task, it is nevertheless vital to include the behaviour of other phenomena at an equivalent level of numerical and physical sophistication. The problems here are twofold - one is concerned with the formulation and representation of the interactions in a manner that enables a computational solution, whilst the second is focussed upon the challenges of implementing appropriate solution strategies and delivering simulation results. A significant part of this problem arises from the fact that the historical development of computational solution procedures and supporting software technologies has taken different routes for each of the main phenomena. Since the modelling of closely coupled physical phenomena requires time and space accurate simulations of all aspects of the calculation, then new kinds of software technologies are required to facilitate this activity. This lecture will address this isue in detail and explore the practical ways forward.

Mark Cross is Professor of Computational Modelling and Director of the Centre for Numerical Modelling and Process Analysis at the University of Greenwich where he has worked for over 20 years. He has a BSc in Mathematics, a PhD in Mathematical Physics and a DSc in Computational Engineering. He has authored over 300 publications and supervised over 40 PhD students. The editor of the Elsevier archival journal, Applied Mathematical Modelling since 1984, he also has an equity stake in three technology start-up companies. He has consulted for a wide range of multi-national technology organisations over the last 20 years or so, including the US Army, NASA, Rio Tinto, Rolls Royce and US Steel. His abiding research interests cover all aspects of computational modelling, from numerical methods through the exploitation parallel systems to strategies and software for the analysis of multi-physics and multi-scale problems.

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Dr Paul MacKerras
IBM

Linux on PowerPC

Abstract
The Linux kernel runs on a wide variety of PowerPC-based machines, ranging from small embedded processors and handhelds to large servers. The rapid maturation of the Linux kernel means that Linux is being used increasingly widely in business and academia, and is now the operating system of choice for most high-performance computing applications. This presentation gives an introduction to and technical overview of Linux on PowerPC machines and talks about some of the interesting ways in which Linux is being used on PowerPC machines today.

Paul MacKerras has been a Linux kernel developer since 1996, when he ported the Linux kernel to run on his Power Macintosh, and has contributed to numerous other open-source projects. He joined the IBM Linux Technology Center in 2001 and is now the PowerPC Linux kernel architect, having overall responsibility within IBM for the parts of the Linux kernel that relate to running on PowerPC-architecture machines. He is also the Linux kernel community maintainer for the 32 and 64-bit PowerPC kernel ports. He has a B.Sc. and a B.E. from the University of Queensland and a Ph.D. in Computer Science from the Australian National University.

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Dr Robert Anderssen
CSIRO
Ausralia

Inverse Problems: A Pragmatist's Approach to the Recovery of Information from Indirect Measurements

Within the class of inverse problems, it is the subclass of indirect measurement problems that characterize the nature of inverse problems that arise in applications. With very few exceptions, measurements only record some indirect aspect of the phenomenon of interest (e.g. X-rays and tomographic images in medical applications; telescope images in astronomy; stereological assessment of biological structure and processes; signatures in geophysical prospecting). Even when the direct information is measured such as weight or length, it is measured as a correlation against a standard and this correlation can be quite indirect, such as the measurement of weight by the extension (compression) of a spring.

The recovery of information about a phenomenon from indirect measurements is a piecemeal process. Any class of indirect measurements can only recover certain information about the phenomenon. In order to formulate realistic mathematical models that relate the indirect measurements to the specific information of the phenomenon that is to be recovered, there is a need to invoke simplifying assumptions (e.g. radial or axial symmetry). The required information about the phenomenon is often only vaguely contained in the available indirect measurements.

All these aspects influence how the recovery of the information can be performed. The choice of methodology is not limited. The challenge is to perform the recovery in a way that correctly reflects the underlying nature of the problem context. It is not a matter of blindly applying some form of quadratic regularization for which algorithms and packages are readily available. Though such tools are useful for initial exploratory analysis, the crucial characterization of the information to be recovered is hidden in the mathematical model that relates the indirect measurements to the phenomenon within the problem context.

When recovering information from indirect measurements, the question that focuses the problem-solving comes from the need for decision-making to have answers to specific matters. The data available for the associated decision-support will be indirect measurements of the phenomenon under investigation. As a consequence of the applications context, the recovery of information of the associated inverse problem will be constrained by practical challenges including:

(i) In a given situation, how does one decide on the indirect measurements to be performed?

(ii) How are some practical people able to solve indirect measurement problems without having to perform an explicit regularization?

(iii) Is there any advantage in combining different indirect measurements of the same phenomenon?

(iv) What are the alternatives, when there is only a (very) limited amount of data?

(v) How does one proceed when a mathematical model is not available or is too complex to formulate?

The talk will examine, in terms of practical problems, how such challenges can be accommodated.

Bob Anderssen grew up in the country in Queensland. He completed an MSc in applied and computational mathematics at the University of Queensland. His PhD in mathematics is from Adelaide. He taught mathematics for one year at Monash before accepting a full time research position in the ANU in computational mathematics. In 1979, because of his keen interest in the application of mathematics to real-world problems, he accepted a position in industrial and computational mathematics in the CSIRO. He has held visiting positions at a number of international universities including Stanford, Princeton, Cambridge (UK), TU-Munich and TU-Vienna, and given invited lectures at an even bigger group including Harvard, Oxford, Ecole Polytechnique and Oberwolfach. He has been president of the Australian Mathematical Society and chair of the National Committee for Mathematics. His current research has focussed on theoretical polymer dynamics, vibrating piano strings (the Stuart piano), the flow and deformation of wheat flour dough from a plant breeding perspective and the drying of pasta. His hobbies include gardening, hiking and classical music.

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Prof. Chaoqun Liu
Center for Numerical Simulation and Modeling
Department of Mathematics
University of Texas at Arlington, USA

High Performance Computation for DNS/LES

The lecture focuses on high order scheme and parallel computation for direct numerical simulation and large eddy simulation for flow separation, transition, wakes, and flow control. A detailed description is given for several fundamental issues such as high quality grid generation, high order scheme for curvilinear coordinates, CFL condition for complex geometry, relation of pseudo-time marching and Richardson iteration, and high-order weighted compact scheme for shock capturing and shock-vortex interaction. The computation examples include DNS for K-type and H-type transition, DNS for flow separation and transition around airfoil with attack angle, control of flow separation by using paused jets, LES simulation for wakes behind juncture of wing and flat plate with wing tip vortex. For DNS of flow transition on flat plate, the calculation has been well validated including friction coefficients and log law of velocity profile. The direct numerical simulation (DNS) for flow separation and transition around a NACA 0012 airfoil with an attack angle of 40 and Reynolds number of 100,000 has been carried out. The details of the flow separation, formation of the detached shear layer, Kelvin-Helmoholtz instability (inviscid shear layer instability) and vortex shedding, interaction of non-linear waves, breakdown, and re-attachment are obtained and analyzed. Though no external disturbances are introduced in the baseline case study, the self-excited mechanism is observed, which may reveal the origin of the disturbance for airfoil with attack angle. The power spectral density of pressure shows the low frequency of vortex shedding caused by the Kelvin-Helmoholt instability dominates from the leading edge to trailing edge. The simulation shows that the nonlinear wave interaction and breakdown is driven by the generation and growth of the stream-wise vortex which leads to the deformation, stretching, and eventually breakdown of the shedding prime vortex. DNS for flow separation control by blowing jets (steady, pulsed, and pitched and screwed jets) is also tested. The effects of unsteady blowing on the surface at the location just before the separation points on the transition and separation are also studied. The separation zone is significantly reduced (almost removed) after unsteady blowing technology is applied. For the case of juncture of wing and flat plate, the wing tip vortex and wakes behind the juncture are well simulated. The computation also shows almost linear growth in efficiency is obtained by using multiple processors.

Dr Chaoqun Lui is currently a Professor in the Department of Mathematics at the University of Texas in the United States. His courses include calculus, numerical analysis, and computational fluid dynamics. Until mid-2000 he was the Director of the Centre for Numerical Simulation and Modeling at the Louisiana Tech University. Dr Lui completed his Doctrate in Applied Mathematics at the University of Colorado in 1989, following a Bachelor and Master of Science (Computational Fluid Dynamics) at Tsinghua University in Beijing. His fields of interest today incorporate Multigrid, DNS/LES, CFD, High-order Discretization, Flow Control, Flow Transition and Turbulence.

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Prof. Denis Evans
Research School of Chemistry, ANU, Canberra ACT 0200 Australia

The Fluctuation Theorem: Simulation, Theory and Experiment

We discuss the close symbiotic relationship that algorithm development has played in the development of new fundamental science. Thermodynamics describes the framework within which all macroscopic processes operate. Until the discovery of the Fluctuation Theorem [1], there was no equivalent framework for small (nano) systems observed for short times. The Fluctuation Theorem provides a generalisation of the Second Law of thermodynamics, that applies to finite systems observed over finite times. The development of this theorem was enabled by development on nonequilibrium molecular dynamics simulation algorithms in the 1980's. These algorithms were convenient dynamical systems that were so close to experimental systems that they enabled the derivation is this generalization of the Second Law of thermodynamics. This extension was first tested with computer simulation[2] and later verified in the laboratory[3]. The Fluctuation Theorem places limits on the operation of nanomachines and biological processes taking place in small organelles. The Theorem states that as "engines" are made ever smaller, the probability that they will operate thermodynamically in reverse, increases exponentially with the size of the system and the duration of operation.

References

[1] Evans, D. J., Cohen, E.G.D. and Morriss, G.P., 1993. Probability of Second Law Violations in Shearing Steady States. Phys. Rev. Lett. 71, 2401- 2402.
[2] Evans, D.J. and Searles, D.J., 2002. The Fluctuation Theorem, Adv. In Phys., 51, 1529 - 1585.
[3] Carberry, D.M., Reid, J.C., Wang, G.M., Sevick, E. M., Searles, D.J. and Evans, D.J., 2004. Phys. Rev. Lett. (To appear). Wang, G.M., Sevick, E.M., Mittag, E., Searles, D.J. and Evans, D. J., 2002. Experimental Demonstration of Violations of the Second Law of Thermodynamics for Small Systems and Short Time Scales. Phys. Rev. Lett. 89, 050601- 4.

Denis Evans has been the Dean of Research School of Chemistry (RSC) at the Australian National University, Canberra, since 1998. His research interests are: Liquid state chemical physics; nonequilibrium statistical mechanics; dynamical systems theory as applied to bulk systems; irreversible thermodynamics; computer simulation algorithms; the relation of the intermolecular potential function to macroscopic fluid properties; molecular rheology.

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Workshops

Immediately following the three days (27-29 September) of invited and contributed presentations there will be two days of workshops (September 30 - October 1). The topics for the CTAC 2004 workshops and contact information for their respective conveners are:

Prof. Roger Tanner - Aspects of Computing with High Viscoelasticity

Prof. Derek Chan - Effective simulation methods for highly charged polymers

Dr Murray Rudman - Modelling of multi-phase systems with complex interfaces

Assoc. Prof. Justin Cooper-White - Simple' fluids in 'simple' flows: drop formation, deformation and impact on solid surfaces

Dr J. Ravi Prakash - Unravelling the dynamics of polymer solutions in extensional flows

Assoc. Prof. Malcolm R. Davidson - Pendant drop formation of shear thinning and yield stress fluids

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  • Dispersed multiphase flows -
    Jiyuan Tu
    jiyuan.tu@rmit.edu.au

    Dispersed multiphase flows are frequently encountered in a variety of industrially important processes in the minerals, petroleum, chemical, metallurgical, nuclear and energy industries. Scale-up of equipment involving dispersed multiphase flows is quite difficult which is mainly due to the inherent complexity of the prevailing flow phenomena (formation of bubbles and clusters in gas-particle flows). During the last decade significant research efforts have been made in both academic and industrial research to study dispersed multiphase flows using computational fluid dynamics (CFD) techniques. This workshop is intended to give an overview of the fundamentals and techniques involved in modeling dispersed multiphase flows. The objective is to discuss recent numerical developments, experimental validation, and its applications in a broad perspective of industries and biomedical research. The workshop will also be an opportunity to present the current state of the art in the area and to identify key future research directions through a panel discussion.

    Lectures (1st October 2004)

    • "Fundamentals of numerically modeling particle-laden multiphase flows"
      By Professor Mark Cross, University of Greenwich

    • "Numerically modeling of gas-liquid flows with or without heat and mass transfer" By Dr Guan Yeoh, ANSTO

    • "CFD modeling of industrial multiphase flows"
      By Dr Phil Schwarz, CSIRO

    • "Modeling of dispersed multiphase flows in other applications"
      By Associate Professor Jiyuan Tu, RMIT University

    • Panel discussion - Issues and Perspectives

      "Numerical modeling of dispersed multiphase flows and experimental validation"

      • Coordinator: Dr Jiyuan Tu
      Professor Mark Cross, Dr Guan Yeoh, Dr Phil Schwarz, Dr William Yang

    • Experimental modeling of dispersed multiphase flows for CFD validation
      By Dr William Yang, CSRIO


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  • High performance computing - A view from the trenches
    Bill Appelbe
    bill@cs.rmit.edu.au

    Traditional scientic computing was done using hand-written Fortran or C programs, running on a single processor. Over the past few years, scientific computing has evolved rapidly in both hardware, software, and tools. This workshop will discuss the current state of the art in scientific computing, emerging trends, and our experiences in scientific software development at VPAC over the past 5 years. The workshop will be divided into 4 sections. Sections will be given by one or more VPAC staff. Each section will include time for open discussion and attendees to share experiences

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Modelling melting and solidification processes is a challenging problem due to the complexity of the coupled heat transfer and fluid flow phenomena, the flow instabilities, the multi-scales and the moving solid/liquid interfaces.

Phase change problems have received considerable research attention over the last two decades. Significant contributions have been made from both the computational fluid dynamics (CFD) and the computational heat transfer (CHT) communities. Numerical methods for fixed grids and for moving grids have been developed with increasing accuracy and performance. But fundamental aspects of melting and solidification problems as well as many applications still elude modelling.

The objective of this symposium is to discuss recent developments on the numerical modelling of solid/liquid phase change problems and its applications with emphasis on heat and mass transfer at the interface. The symposium will be an opportunity to present the current state of the art in the area and to identify key future research directions.

This will provide an excellent opportunity for the interaction of the French and Australian scientific communities on the application of CFD and Applied Mathematics to heat and mass transfer problems.

Abstracts:

 

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Proceedings

A refereed proceedings will be published after the conference in the Electronic Supplement of the ANZIAM Journal (http://anziamj.austms.org.au/).
Acceptance of papers for inclusion in the proceedings will be determined by peer review.

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Organised by

Computational Mathematics Group
of the Australian Mathematics Society