[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Preface Part I. Turbulence: 1. Introduction 2. Coherent structures 3. Proper orthogonal decomposition 4. Galerkin projection Part II. Dynamical Systems: 5. Qualitative theory 6. Symmetry 7. One-dimensional 'turbulence' 8. Randomly perturbed systems Part III. 9. Low-dimensional Models: 10. Behaviour of the models Part IV. Other Applications and Related Work: 11. Some other fluid problems 12. Review: prospects for rigor Bibliography.

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Turbulence, Coherent Structures, Dynamical Systems and Symmetry

The understanding of fluid turbulence has considerably progressed in recent years. The application of the methods of statistical mechanics to the description of the motion of fluid particles, i.e., to the Lagrangian dynamics, has led to a new quantitative theory of intermittency in turbulent transport. The first analytical description of anomalous scaling laws in turbulence has been obtained. The underlying physical mechanism reveals the role of statistical integrals of motion in nonequilibrium systems. For turbulent transport, the statistical conservation laws are hidden in the evolution of groups of fluid particles and arise from the competition between the expansion of a group and the change of its geometry. By breaking the scale-invariance symmetry, the statistically conserved quantities lead to the observed anomalous scaling of transported fields. Lagrangian methods also shed new light on some practical issues, such as mixing and turbulent magnetic dynamo.

/pdf/particles-and-fields-in-fluid-turbulence-f80f8gqw2g.pdf

Particles and fields in fluid turbulence

To improve the performance of particle image velocimetry in measuring instantaneous velocity fields, direct cross-correlation of image fields can be used in place of auto-correlation methods of interrogation of double- or multiple-exposure recordings. With improved speed of photographic recording and increased resolution of video array detectors, cross-correlation methods of interrogation of successive single-exposure frames can be used to measure the separation of pairs of particle images between successive frames. By knowing the extent of image shifting used in a multiple-exposure and by a priori knowledge of the mean flow-field, the cross-correlation of different sized interrogation spots with known separation can be optimized in terms of spatial resolution, detection rate, accuracy and reliability.

Theory of cross-correlation analysis of PIV images : Image analysis as measuring technique in flows

https://iopscience.iop.org/article/10.1016/0169-5983(92)90023-P/pdf

New Insights into Large Eddy Simulation

Pressure Fields and Cavitation in Turbulent Shear Flows

Mass transfer studies across ventilated hydrofoils: A step towards hydroturbine aeration

I (GB) was fortunate that early in my career I had the opportunity to work with Keith Glover. Keith had just begun his obsession with golf. A simple game where a ball stands still and the player advances it from different parts of the landscape into a hole. During a golf outing, Keith vigorously struck a ball off the fairway. It drove through a water hazard and miraculously ended up a few feet off the green. I was amazed by the image I saw as the ball moved through the water. Due to its velocity, a cavitation bubble was generated behind it. I had no inkling that my golf outing with Keith would lead many years later to an interest in the control of supercavitating vehicles.

http://www.aem.umn.edu/research/documents/Springer.pdf

Control of high-speed underwater vehicles

In this paper, a linear mathematical model of a supercavitating vehicle is developed to investigate some of the physical factors affecting stability and control. This model provides a link between the simulation dynamics and the assumed physical vehicle characteristics. In this paper, the static and dynamic stability of the pitch plane dynamics of the vehicle is considered and the effect of cavitator shapes, namely a disk cavitator, a 45 cone, and a 15 cone on the vehicle stability, is determined. All three cavitator shapes resulted in unstable vehicles when operating in nonplaning conditions, with the disk cavitator the least destabilizing. Neglecting the small tangential forces on the disk cavitator is confirmed to be reasonable, but in general, the vehicle static stability characteristics depend on the cavitator tangential forces. The vehicle mathematical model uses static experimental data of hydrodynamic coefficients for the disk cavitator.

Roger E. A. Arndt

Papers

Pressure Fields and Cavitation in Turbulent Shear Flows

Mass transfer studies across ventilated hydrofoils: A step towards hydroturbine aeration

Control of high-speed underwater vehicles

Effect of Cavitator on Supercavitating Vehicle Dynamics

Semiempirical Analysis of Cavitation in the Wake of a Sharp-Edged Disk