IUTAM Symposium on Simulation and Identification of Organized Structures in Flows

The dynamics of transitional and turbulent flows is often dominated by organized structures with a life-time much longer than a characteristic time scale of the surrounding small-scale turbulence. Organized structures may appear as secondary flows as a result of an instability but they persist in turbulent flows. They manifest themselves as eddies or localized vortices and play an important role in e.g. mixing and transport processes. Al though the existence of organized structures has been revealed by many experiments and by numerical simulations they are somewhat elusive, as there is no consensus on how to define them and technically how to detect them. In recent years several identification tools for analysing complex flows have been developed. These tools include various versions of the Proper Orthog onal Decomposition (POD) technique, wavelet transforms, pattern recogni tion, etc. At the same time, improvements in experimental techniques have made available data that further necessitate efficient detection methods. A prominent example is the Particle Image Velocimetry (PIV) technique from which complex spatio-temporal flow data can be obtained. An interesting feature of some of the identification techniques is that they form the basis for reduced models by which dynamical processes can be studied in details. From studies of dissipative dynamical systems it has been revealed that, in phase space, transitional and turbulent flows can be identified by their low-dimensional behaviour. Thus, employing data from experiments or nu merical simulations to form modes residing on finite-dimensional attractors may dramatically reduce computing costs.

Résumé
`I have read this book with great interest and found that most papers provide something new, inspiring, and applicable in hydraulic research. In summary, this book is a valuable source of information that should stimulate new approaches and developments in hydraulic research, especially in studying the physics of hydraulic resistance, sediment transport, flow-biota interactions, and their modeling.'
Journal of Hydraulic Engineering (February 2001)

Contenu
I. Flow Control.- Taming Near-Wall Streamwise Vortices: A Modus Operandi for Boundary Layer Control.- Visualization of Coherent Structures in Manipulated Turbulent Flow over a Fence.- Experimental Study of Temporal and Spatial Structures in Fence-on-Wall Testcase.- II. Coherent Structures in Wall-Bounded Flows.- Dynamics of the Structures of Near Wall Turbulence.- Three Dimensional Configuration of a Large-Scale Coherent Vortex in a Turbulent Boundary Layer.- Formation of Near-Wall Streamwise Vortices by Streak Instability.- III. Rotating Flows.- Organized Structures in Rotating Channel Flow.- Simulation and Identification of Organized Vortices in Rotating Turbulent Flows.- On the Space-Time Structure of Axisymmetric Rotating Flows.- Observations on the Early Transition Process in a Closed Cylindrical Container with Rotating Bottom.- Shear Flow Instability in a Rotating Fluid Layer.- IV. Small-Scale Turbulence and 2-D Flows.- Identification of Coherent Fine Scale Structure in Turbulence.- Evolution of Vortical Structure in Isotropic Turbulence.- Fractal and Spiral Organised Structures: Spectra and Diffusion.- V. Geostrophic and Stratified Flows.- Vortex Wakes in Stably-Stratified Fluids.- Baroclinic Tripolar Geostrophic Vortices.- Vertical Alignment of Geostrophic Vortices.- The Interaction of a Vortex With a Stable Jet.- VI. Topological Aspects.- Streamline Topology of Axisymmetric Flows.- Flow Topology and Tomography for Vortex Identification in Unsteady and in Three-Dimensional Flows.- Coherent Structures in Fluids are Topological Torsion Defects.- The Vortex Concept and its Identification in Turbulent Boundary Layer Flows.- VII. Experimental Techniques.- Coherent Structures Identification in Separated and Free Mixing Layers using Hot Wire Rakes.- 3D Mesurement of Vortex Structures in Stratified Fluid Flows.- DNS of a Turbulent Channel Flow to Guide Vorticity Measurements in the Wall Region.- Quantitative Planar Imaging of Large Structures Developed Through the Precession of a Jet.- VIII. Vortical Structures.- Formation of Vortex Rings in Helicopter Rotor Flow Fields.- Three-Dimensional Vortical Structure and Diffusion Mechanism of an Excited Rectangular Jet.- Identification of Strong, Near-Wall Quasi-Streamwise Vortices and Their behavior.- Three Dimensional Coherent Structures in the Flow Around a Circular Cylinder by Direct Numerical Simulation.- IX. POD, LSE and Other Techniques.- Detection and Identification of Near-Wall Coherent Structures Through Conditional-Sampling.- Organized Structure Dynamics in a Turbulent Round Jet.- Examination of a LSE/POD Complementary Technique using Single and Multi-Time Information in the Axisymmetric Shear Layer.- Conditional Vortical Structures of a Plane Jet Based on the Complementary LSE/POD Technique.- Application of POD to PIV Images of Flow Over a Wall Mounted Fence.- Structure Detection in Driven Drift Wave Turbulence.- A Coherent Structure Detection Method Using the Wavelet Transform.- X. Low-Dimensional Modelling.- Multi-Point Measurements and Low-Dimensional Models: Tools for the Characterization and Control of Turbulent Flows.- Large Eddy Simulation of a Spatially Developing 3D Shear Layer in Incompressible Flow: Comparisons with Detailed Experiments.- Low-Dimensional Study of the Flow Between Two Counter-Rotating Disks.- Sinuous and Varicose Modes in Phase-Locked Interaction.- Analytical Identification of Galloping Effects on Prismatic Bodies.- Multiresolution Local Adaptive Method for the Analysis of Spatially Extended Systems.- Energy Transfer Between Coherent Structures in the Wake of a Hemisphere.- List of Participants.- Author Index.