This book concerns the presentation of particle velocity measurement for acoustics using lasers, including Laser Doppler Velocimetry (LDV or Anemometry (LDA)) and Particle Imagery Velocimetry (PIV). The objective is first to present the importance of measuring the acoustic velocity, especially when the acoustic equations are nonlinear as well as characterizing the near fields. However, these applications need to use non-invasive sensors. Some optical techniques, initially developed for fluid mechanics, have been adapted to the field of acoustics in recent years. This book summarizes 15 years of research in this area, highlighting the improvements that have been made, particularly in signal processing, and showing applications for which they have proven to be a carrier of innovation.

This book concerns the presentation of particle velocity measurement for acoustics using lasers, including Laser Doppler Velocimetry (LDV or Anemometry (LDA)) and Particle Imagery Velocimetry (PIV). The objective is first to present the importance of measuring the acoustic velocity, especially when the acoustic equations are nonlinear as well as characterizing the near fields. However, these applications need to use non-invasive sensors. Some optical techniques, initially developed for fluid mechanics, have been adapted to the field of acoustics in recent years. This book summarizes 15 years of research in this area, highlighting the improvements that have been made, particularly in signal processing, and showing applications for which they have proven to be a carrier of innovation.

This book is the result of two decades of research work which started with an accidental observation. One of my students, Dipl. phys. Volkmar Lenz, - ticed that the speckle pattern of laser light scattered by a cuvette containing diluted milk performed a strange motion every time he came near the cuvette with his thumb. After thinkingabout this e?ect we came to the conclusion that this motion can only be caused by scatteringparticles with di?erent velocities, as in the case of the di?raction pattern of an optical grating: A linear motion of the grating does not change the pattern whereas a rotation of the grating does. The observed speckle motion could then be explained qualitatively as produced by the inhomogeneous velocity of the convection within the cuvette which was produced by the heat of the thumb. The theoretical treatment of this e?ect revealed that the velocity gradient of the light scattering medium is responsible for the speckle motion. The idea to use this e?ect for developingmeasurement techniques for velocity gradients arose almost immediately. For that purpose we had to develop not only experimental set-ups to measure the pattern velocity but also the theory which describes the connection between this velocity and the velocity gradient. The result of this work together with the description of a method developed by another group forms the contents of this book. I am indebted to the students who worked in my laboratory and developed the measurement techniques. These were, in temporal order, Dr.

Providing the first comprehensive treatment, this book covers all aspects of the laser Doppler and phase Doppler measurement techniques, including light scattering from small particles, fundamental optics, system design, signal and data processing, tracer particle generation, and applications in single and two-phase flows. The book is intended as both a reference book for more experienced users as well as an instructional book for students. It provides ample material as a basis for a lecture course on the subject and represents one of the most comprehensive treatments of the phase Doppler technique to date. The book will serve as a valuable reference book in any fluid mechanics laboratory where the laser Doppler or phase Doppler techniques are used. This work reflects the authors' long practical experience in the development of the techniques and equipment, as the many examples confirm.

This report provides a basis for assessing the feasibility of using a laser doppler velocimeter for the measurement of low amplitude acoustic particle velocity in the sea at very low frequencies. (Author).