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Optical Doppler Velocimetry

Doppler (XT Optical coherence imaging Optical Doppler tomography (ODT) Optical Doppler velocimetry... [Pg.2529]

Campbell and Hanratty (1982) used Lau s (1980) measurements with some special optics on a laser Doppler velocimetry system to calculate /3(f) near a fixed interface, in this case, the inside of a clear pipe. They determined w(z,t) from equation (8.52), and solved equations (8.49) and (8.50) numerically for / l(0- Finally, they applied equation (8.51) to determine Kl, which has been the goal all along. The end results (Kl) may then be related to the other, independent parameters that are important to the transfer process, such as diffusivity, viscosity, and turbulence parameters. Campbell and Hanratty performed this operation and found the following correlation ... [Pg.220]

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] ... [Pg.100]

Unambiguous determination of the conditions under which slippage occurs requires a technique able to measure the velocity of the fluid in the immediate vicinity of the solid wall over a thickness comparable to the size of a polymer chain, i.e. a few tens of nanometers. Classical laser Doppler velocimetry does not meet this requirement even if it allows for the determination of velocity profiles which clearly reveal a non-zero velocity within typically a few 10 pm from the wall. We have developed a new optical technique. Near Field Velocimetry (N.F.V.) [14], which combines Evanescent Wave Induced Fluorescence (E.WF.) [27] and Fringe Pattern Fluorescence Recovery After Photobleaching (F.P.F.R.A.P.) [28]. The former technique gives the spatial resolution normal to the solid wall, while the latter one enables the determination of the local velocity of the fluid. A major constraint of the technique is that it needs polymer molecules labelled with an easily photobleachable fluorescent probe. [Pg.338]

Agrawal, Y., Quadrature demodulation in laser Doppler velocimetry. Applied Optics, 23, 1685-1686 (1984)... [Pg.310]

Adrian, R.J., ed. Selected Paper on Laser Doppler Velocimetry. SPIE Vol. MS 78, SPIE Optical Engineering Press, 617 pp (1993). [Pg.348]

An attractive feature of fiber sensors is the possibility of performing in vivo tests and monitoring. Numerous fiber-optic sensors have already been described that measure physical parameters of the human body [41]. Pressure, temperature, physiological flow, strain, motion, displacement, or flow velocity can be monitored by optical methods such as variable reflection, laser Doppler velocimetry, optical holography, or diffraction. In this section the application of optosensing methods to the determination of molecular species encountered in clinical and biomedical analysis is described. [Pg.241]

The stainless steel high-pressure vessel used for the flow measurements, designed by ITTB Heerenveen (The Netherlands), is presented in Fig. 3.2. The vessel has an internal diameter of 6 cm and is designed for pressures up to 15 MPa. The temperature is controlled by pumping water from a thermostatic bath through channels in the vessel wall. Pitched-blade impellers with a diameter of half the vessel diameter are used to stir the vessel content. Two glass windows allow for measurement of velocity components in three directions with laser-Doppler velocimetry. The LDV equipment consists of a 2D fiber optics system... [Pg.39]

Optical techniques, i.e., laser Doppler velocimetry O DV), particle image velocimetry (PIV), and holographic PIV, have matured as successful nonintrusive velocity measurement techniques for large-scale applications. Panigrahi et al. [2] obtained the shear stress from PIV measurements by assuming the validity of law of the wall for turbulent flow. In recent years, the p-PIV has matured as a successful velocity measurement technique for MEMS applications [3]. [Pg.2963]

Laser Doppler Velocimetry (LDV) (Joshi et al. 2001) and PDA (Schafer et al. 2000) are optical techniques that have been used to determine BSDs, gas hold-up and flow patterns. Detectors observe the Doppler shift and phase difference when bubbles pass through the volume of the intersection of two laser beams. Doppler effect is related to the velocities of bubbles and the phase difference is related to the sizes of bubbles. Particle Image Velocimetry (PIV)... [Pg.774]

Particle based flow visualization techniques introduce marker particles into the flow field to study the motion of the bulk by determining the velocity vectors associated with these particles. Laser Doppler velocimetry (LDV), optical Doppler tomography (ODT) and particle image velocimetry (PIV) are the different methods that have been developed in this regard. However, of these methods microscale PIV ( x-PIV) is the most well-developed and popular microscale flow visualization technique. [Pg.1326]

Spray properties are mostly determined with optical measurement techniques. For the analysis of the droplet diameter Shadowgraphic methods, laser diffraction or Phase Doppler Anemometry (PDA) have been used elsewhere [1, 2, 11, 18]. Droplet velocities can be measured with Shadowgraphy, Particle Image Velocimetry (PIV), or PDA [1, 6, 19]. The determination of the spray temperature is possible with Global Rainbow Thermometry (GRT), Planar Laser Induced Fluorescence (PLIF), and Differential Infrared Thermography (DIT) [20-22]. [Pg.612]

Our understanding of the hydrodynamics of multiphase flows has progressed substantially in the recent three decades, thanks to the development of advanced experimental techniques, particularly laser Doppler anemometry (LDA), particle image velocimetry (PIV), computer-automated radioactive particle tracking (CARPT), and optical bubble probes. In addition, computational fluid dynamics (CFD) simulations allow for inner views in two-phase process equipment. [Pg.284]


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