Laser Doppler measurement technique

Kried, D. K.,J. M.Creer,J. M. Bates, M. S. Quigley, A. M. Sutey, and D. S. Rowe, 1979, Fluid Flow Measurements in Rod Bundles Using Laser Doppler Anemometry Techniques, Fluid Flow and Heat Transfer over Rod or Tube Bundles, p. 13, ASME Winter Annual Meeting, ASME, New York. (3) Kudryavtsev, A. P., D. M. Ovechkin, D. N. Sorokin, V. I. Subbotin, and A. A. Tsyganok, 1967, Transfer... 

Albrecht, H. E., Borys, M., Damaschke, N., and Tropea, C. Laser Doppler and Phase Doppler Measurement Techniques. Berlin Springer, 2003. 

F. Durst, G. Richter, Laser Doppler measurements of wind velocities using visible radiation, in Photon Correlation Techniques in Fluid Mechanics, ed. by E.O. Schulz-Dubois. Springer Ser. Opt. Sci., vol. 38 (Springer, Berlin, 1983), p. 136... 

Albrecht H, Borys M, Damaschke N, Tropea C (2003) Laser-Doppler and phase-Doppler measurement techniques. Springer, Heidelberg... 

Small values of the electrophoretic mobility [even smaller than 0.1 (ps)/(v/cm)] can be measured using the laser-Doppler electrophoretic technique. This aspect is particularly important when the mobilities involved are small in magnitude and are in the region close to the point of zero charge. 

The traditional microscopic method is complicated by the electro-osmotic velocity due to the negatively charged glass walls of the cell. There is only one particular region between the wall and the center of the cell, which is called the stationary layer, where the particles move with a velocity that is due solely to their charge. It is difficult to consistently focus the microscope in this layer with classical methods. However, the laser-Doppler electrophoretic technique overcomes this difficulty by accurately measuring the particle s velocity in the stationary layer. 

Electrophoretic mobility measurements for various soluble salts were performed by the laser-Doppler electrophoretic technique. The Zetasizer 3 with AZ4 standard cell was used for measuring the electrophoretic mobilities. 

Comparisons between velocity and turbulence results measured using the LDV (Laser Doppler Velocimetry) technique and CFD modeling were done. The predicted velocity components agreed well with the values obtained from LDV. The standard k-e model underpredicts the k level in the flotation cell compared to measured values. 

Yu PY, Varty RL (1988) Laser-Doppler measurement of the velocity and diameter of bubbles using the triple-peak technique. Int J Multiph How 14(6) 765-776... 

Laser Doppler Velocimeters. Laser Doppler flow meters have been developed to measure Hquid or gas velocities in both open and closed conduits. Velocity is measured by detecting the frequency shift in the light scattered by natural or added contaminant particles in the flow. Operation is conceptually analogous to the Doppler ultrasonic meters. Laser Doppler meters can be appHed to very low flows and have the advantage of sensing at a distance, without mechanical contact or interaction. The technique has greatest appHcation in open-flow studies such as the deterrnination of engine exhaust velocities and ship wake characteristics. 

The laser-Doppler anemometer measures local fluid velocity from the change in frequency of radiation, between a stationary source and a receiver, due to scattering by particles along the wave path. A laser is commonly used as the source of incident illumination. The measurements are essentially independent of local temperature and pressure. This technique can be used in many different flow systems with transparent fluids containing particles whose velocity is actually measured. For a brief review or the laser-Doppler technique see Goldstein, Appl. Mech. Rev., 27, 753-760 (1974). For additional details see Durst, MeUing, and Whitelaw, Principles and Practice of Laser-Doppler Anemometry, Academic, New York, 1976. 

The flow patterns for single phase, Newtonian and non-Newtonian liquids in tanks agitated by various types of impeller have been repotted in the literature.1 3 27 38 39) The experimental techniques which have been employed include the introduction of tracer liquids, neutrally buoyant particles or hydrogen bubbles, and measurement of local velocities by means of Pitot tubes, laser-doppler anemometers, and so on. The salient features of the flow patterns encountered with propellers and disc turbines are shown in Figures 7.9 and 7.10. 

The brief history, operation principle, and applications of the above-mentioned techniques are described in this chapter. There are several other measuring techniques, such as the fluorometry technique. Scanning Acoustic Microscopy, Laser Doppler Vibrometer, and Time-of-flight Secondary Ion Mass Spectroscopy, which are successfully applied in micro/nanotribology, are introduced in this chapter, too. 

Laser Doppler Vibrometry (LDV) is a sensitive laser optical technique well suited for noncontact dynamic response measurements of microscopic structures. Up to now, this technology has integrated the micro-scanning function for... 

Liu et aU622] used a laser Doppler velocity and size (LDVS) measurement technique to determine the local size, velocity, and number flow density of droplets in the spray cone during spray deposition of a liquid steel. The experimental setup is schematically depicted in Fig. 6.7.1615] The measured results showed that smaller... 

Flow patterns of hydrodynamic systems like the compendial dissolution apparatus may be qualitatively characterized by means of dilute dye injection (e.g., methylene blue) or by techniques using particulate materials such as aluminum powders or polystyrene particles. Flow patterns may be also visualized by taking advantage of density or pH differences within the fluid stream. The Schlieren method, for instance, is based on refraction index measurement. Hot wire anemo-metry is an appropriate method to quantitatively characterize flow rates. The flow rate is proportional to the cooling rate of a thin hot wire presented to the stream. Using laser Doppler... 

There have been several studies in which the flow patterns within the body of the cyclone separator have been modelled using a Computational Fluid Dynamics (CFD) technique. A recent example is that of Slack et a/. 54 in which the computed three-dimensional flow fields have been plotted and compared with the results of experimental studies in which a backscatter laser Doppler anemometry system was used to measure flowfields. Agreement between the computed and experimental results was very good. When using very fine grid meshes, the existence of time-dependent vortices was identified. These had the potentiality of adversely affecting the separation efficiency, as well as leading to increased erosion at the walls. 

NMR imaging techniques were applied to the measurements of velocity field in opaque systems such as tomato juice and paper pulp suspensions [58-60]. In both cases, the particle concentrations are sufficiently high that widely applied techniques such as hot film and laser Doppler anemometry could not be used. The velocity profile for a 6 % tomato juice slurry clearly showed a power-law behavior [58, 59]. Row NMR images for a 0.5 % wood pulp suspension provided direct visual of three basic types of shear flow plug flow, mixed flow and turbulent flow as mean flow rate was increased. Detailed analysis of flow NMR image is able to reveal the complex interaction between the microstructure of suspensions and the flow [60]. 

The methods described in this book are primarily concerned with the measurement of the microstructure of complex fluids subject to the application of external, orienting fields. In the case of flow, it is also of interest to measure the kinematics of the fluid motion. This chapter describes two experimental techniques that can be used for this purpose laser Doppler velocimetry for the measurement of fluid velocities, and dynamic light scattering (or photon correlation spectroscopy) for the determination of velocity gradients. 

Laser Doppler velocimetry is a powerful technique for the in situ measurement of fluid velocities. The basic optical configuration for the measurement is shown in Figure 6.1. The velocity measurement is made at the intersection of two laser beams that are focused to a point in the flow. The use of laser radiation is essential since the light must be monochromatic and coherent. This is required since the intersection of the two beams must create an interference pattern within the fluid. Such a pattern is shown in Figure 6.2, where two plane waves intersect at an angle 2(J). The two waves will have the following form [55] ... 

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