Laser Velocimetry In Fluid Mechanics

In fluid mechanics, velocity measurement is fundamental in order to improve the behavior knowledge of the flow. Velocity maps help us to understand the mean flow structure and its fluctuations, in order to further validate codes. Laser velocimetry is an optical technique for velocity measurements; it is based on light scattering by tiny particles assumed to follow the flow, which allows the local fluid flow velocity and its fluctuations to be determined. It is a widely used non-intrusive technique to measure velocities in fluid flows, either locally or in a map. This book presents the various techniques of laser velocimetry, as well as their specific qualities: local measurements or in plane maps, mean or instantaneous values, 3D measurements. Flow seeding with particles is described with currently used products, as well as the appropriate aerosol generators. Post-processing of data allows us to extract synthetic information from measurements and to perform comparisons with results issued from CFD codes. The principles and characteristics of the different available techniques, all based on the scattering of light by tiny particles embedded in the flow, are described in detail; showing how they deliver different information, either locally or in a map, mean values and turbulence characteristics.

In the tradition of its predecessors, this volume comprises a selection of the best papers presented at the Ninth International Symposium on Applications of Laser Techniques to Fluid Mechanics, held in Lisbon in July 2000. The papers reflect the state-of-the-art in laser applications of laser techniques in fluid mechanics describing novel ideas for instrumentation, instrumentation developments, results of measurements of wall-bounded flows, free flows and flames and flow and combustion in engines. The papers demonstrate the continuing interest in the development of an understanding of new methodologies and implementation in terms of new instrumentation.

This volume includes revised and extended versions of selected papers presented at the Tenth International Symposium on Applications of Laser Techniques to Fluid Mechanics held at the Calouste Gulbenkian Foundation in Lisbon, during the period of July 10 to 13, 2000. The papers describe instrumentation developments for Velocity, Scalar and Multi-Phase Flows and results of measurements of Turbulent Flows, and Combustion and Engines. The papers demonstrate the continuing and healthy interest in the development of understanding of new methodologies and implementation in terms of new instrumentation. The prime objective of the Tenth Symposium was to provide a forum for the presentation of the most advanced research on laser techniques for flow measurements, and communicate significant results to fluid mechanics. The application of laser techniques to scientific and engineering fluid flow research was emphasized, but contributions to the theory and practice of laser methods were also considered where they facilitate new improved fluid mechanic research. Attention was placed on laser-Doppler anemometry, particle sizing and other methods for the measurement of velocity and scalars, such as particle image velocimetry and laser induced fluorescence.

This volume comprises a selection of the best papers presented at the Seventh Interna tional Symposium on Applications of Laser Techniques to Fluid Mechanics held at The Calouste Gulbenkian Foundation in Lisbon, during the period of July 11 to 14,1994. The papers describe Applications to Fluid Mechanics, Applications to Combustion, Instrumentation for Velocity and Size Measurements and Instrumentation for Whole Field Velocity and demonstrate the continuing and healthy interest in the development of understanding of the methodology and implementation in terms of new instru mentation. The prime objective of this Seventh Symposium was to provide a forum for the presen tation of the most advanced research on laser techniques for flow measurements, and communicate significant results to fluid mechanics. The applications oflaser techniques to scientific and engineering fluid flow research was emphasized, but contributions to the theory and practice of laser methods were also considered where they facilitate new improved fluid mechanic research. Attention was placed on laser-Doppler anemometry, particle sizing and other methods for the measurement of velocity and scalar, such as particle image velocimetry and laser induced fluorescence. We would like to take this opportunity to thank those who participated. The assistance provided by the Advisory Committee, by assessing abstracts was highly appreciated.

This volume consists of papers selected from the proceedings of the Fifth International Symposium on Applications of Laser Techniques to Fluid Mechanics, held at the Calouste Gulbenkian Foundation in Lisbon from 9 to 12 July, 1990. Relative to previous meetings in the Lisbon series the scope of this symposium was broadened by expanding the topical coverage to include all laser techniques used in fluid mechanics. This change recognized the trend amongst experimental fluid dynamicists to employ laser techniques for the mea surement of many different quantities, including concentration, temperature, particle size, and velocity, and the need for researchers to have a forum in which to communicate their work and share their common interests. The Fifth Symposium contained twenty-three sessions of formal presentations and a lively Open Forum ses sion. In addition, Dr. H. J. Pfeiffer organized a special Workshop on the Use of Computers in Flow Mea surements which contained five sessions on frequency domain processors, correIa tors, special detectors, and biasing.

In fluid mechanics, non-intrusive measurements are fundamental in order to improve knowledge of the behavior and main physical phenomena of flows in order to further validate codes. The principles and characteristics of the different techniques available in laser metrology are described in detail in this book. Velocity, temperature and concentration measurements by spectroscopic techniques based on light scattered by molecules are achieved by different techniques: laser-induced fluorescence, coherent anti-Stokes Raman scattering using lasers and parametric sources, and absorption spectroscopy by tunable laser diodes, which are generally better suited for high velocity flows. The size determination of particles by optical means, a technique mainly applied in two-phase flows, is the subject of another chapter, along with a description of the principles of light scattering. For each technique the basic principles are given, as well as optical devices and data processing. A final chapter reminds the reader of the main safety precautions to be taken when using powerful lasers.

A novel monobeam Distributed Laser Doppler Velocimeter, DLDV, that permits a fast recovery of the flow profile is described. The DLDV use of low-coherence multiplexing concept, along a reference-beam backscattering LDV scheme, to realize a remote addressing of the flow point. The experimental results of flow profile recovery by an all fiber DLDV implementation is reported along with a theoretical analysis of the novel scheme. The results confirm the exceptional capabilities offered by the DLDV in experimental fluid mechanics. (Author).

This revised edition provides updated fluid mechanics measurement techniques as well as a comprehensive review of flow properties required for research, development, and application. Fluid-mechanics measurements in wind tunnel studies, aeroacoustics, and turbulent mixing layers, the theory of fluid mechanics, the application of the laws of fluid mechanics to measurement techniques, techniques of thermal anemometry, laser velocimetry, volume flow measurement techniques, and fluid mechanics measurement in non-Newtonian fluids, and various other techniques are discussed.