Doppler anemometry

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. 

Velocity vectors of the gas flow measured using laser Doppler anemometry inside a closed chamber during the formation of a tulip flame. Images of the flame are also shown, though the velocity measurements required many repeated runs, hence, the image is only representative. The chamber has square cross sections of 38.1mm on the side. The traces in the velocity fields are the flame locations based on velocity data dropout. The vorticity generated as the flame changes shape appears clearly in the velocity vectors. 

Laser Doppler anemometry data showing the axial velocity along the centerline of a 380 mm long closed chamber during the formation of acetylene/air tulip flames of different equivalence ratios. The velocity is measured 265 mm from the ignition thus, the tulip shape is already formed before the flame reaches the measurement point. This work shows the behavior similar to the results described in Figure 5.3.9. (Adapted from Starke, R. and Roth, R, Combust. Flame, 66,249,1986.)... 

Phase doppler anemometry Cumulative with time >0.5a Limited to droplets, sampling 53... 

JA Ranucci, FC Chen. Phase doppler anemometry a technique for determining aerosol plume-particle size and velocity. Pharm Technol 17 62-74, 1993. 

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... 

In view of the different requirements as to computer power, it is very worthwhile to compare the outcome of RANS and LES simulations mutually and/ or with quantitative experimental data. Several authors have done this, e.g., Derksen and Van den Akker (1998, 1999), Derksen (2001), Lu et al. (2002), Ranade (2002), Derksen (2002b), and Yeoh et al. (2004a,b). In most cases, the experimental data have been obtained by means of Laser-Doppler Anemometry (LDA, or LDV) see, e.g., Yianneskis et al. (1987), Wu and Patterson (1989), Schafer et al. (1997, 1998), and Derksen et al. (1999). In this review, we will mainly refer to the validation study due to Hartmann et al. (2004a). 

Phase-Doppler Anemometry. Theoretical analyses on dualbeam light scattering with off-axis detection 670 showed that the spatial frequency of the scattered interference fringe pattern is... 

In homogeneous turbulence, the one-point joint velocity PDF can be written as /u(V t), and can be readily measured using hot-wire anemometry or laser Doppler velocimetry (LDV). 

Electrophoretic mobility measurements can be performed by laser Doppler anemometry (LDA). LDA is fast and capable of high resolution of particle velocities [144]. It measures particle velocity, which is measured in the stationary... 

There have been very few studies of the effects of non-Newtonian properties on flow patterns in hydrocyclones, although Dyakowski et al.,AU have carried out numerical simulations for power-law fluids, and these have been validated by experimental measurements in which velocity profiles were obtained by laser-doppler anemometry. 

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. 

Capillary hydrodynamic chromatography Fraunhofer diffraction Light-scattering photometry Phase Doppler anemometry Ultrasonic spectroscopy... 

With the aid of the two-color Laser-Doppler-Anemometry (LDA), Bewersdorff was able to measure the axial and the radial turbulence intensities simultaneously and also the Reynolds shear stresses. The injection of polymer results in a damping of both intensities in the region of their maxima. In his Reynolds shear stress measurements he showed that the polymer injection results in a drastic damping, and the stress maximum is shifted towards the center of the pipe. In a homogeneous polymer solution the maximum of the Reynolds shear stress remains in the same position-as for water. Only in the region of the buffer zone are the shear stresses reduced. 

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]. 

F. Durst, A. Melling, and J. H. Whitelaw, Principles and practice of laser-Doppler anemometry, Academic Press, New York (1976). 

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