Laser Doppler velocimetry LDV

Measuring particle size from the peak amplitude of a LDV signal was first done on combustion flows [154,155]. A later paper discussed the errors associated with this method and proposed procedures to correct for them [156]. Types of error include  

1 The possibility of more than one particle being in the sample volume at the same time  

2 Particles only partly in the control volume being counted as smaller particles  

3 The dependence of the light scattering signal magnitude on the particle s location in the sample volume  

4 The dependence of the sample volume size on the particle s apparent diameter since larger particles have a larger effective sample volume due to the Gaussian intensity distribution of the laser beam. 

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This system produces a steady laminar flow with a flat velocity profile at the burner exit for mean flow velocities up to 5m/s. Velocity fluctuations at the burner outlet are reduced to low levels as v /v< 0.01 on the central axis for free jet injection conditions. The burner is fed with a mixture of methane and air. Experiments-described in what follows are carried out at fixed equivalence ratios. Flow perturbations are produced by the loudspeaker driven by an amplifier, which is fed by a sinusoidal signal s)mthesizer. Velocity perturbations measured by laser doppler velocimetry (LDV) on the burner symmetry axis above the nozzle exit plane are also purely sinusoidal and their spectral... 

There are many nonintrusive experimental tools available that can help scientists to develop a good picture of fluid dynamics and transport in chemical reactors. Laser Doppler velocimetry (LDV), particle image velocimetry (PIV) and sonar Doppler for velocity measurement, planar laser induced fluorescence (PLIF) for mixing studies, and high-speed cameras and tomography are very useful for multiphase studies. These experimental methods combined with computational fluid dynamics (CFDs) provide very good tools to understand what is happening in chemical reactors. 

See also Planar cavity surface-emitting laser (PCSEL) diodes Vertical cavity surface-emitting laser (VCSEL) diodes compound semiconductor-based, 22 179 Laser Doppler velocimetry (LDV), 11 784 Laser Doppler velocimeters, 11 675 Laser-drilled surgical needles, 24 206 Laser dye energy levels, 14 702-703 Laser fabrication techniques, titanium, 24 857... 

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). 

In an earlier phase of this work [9] the intensities of axial and circumferential components of velocity fluctuation were measured in the TC annulus, using Laser Doppler Velocimetry (LDV), for a wide range of cylinder rotation speeds. On average, the intensities of axial velocity fluctuations were found to be within 25% of the intensities of circumferential velocity fluctuations [9]. As in Ronney et al. [5], turbulence intensities were found to be nearly homogeneous along the axial direction and over most of the annulus width, and to be linearly proportional... 

There are two commonly applied ELS experimental methods laser Doppler electrophoresis (LDE) [ 111, a subset of laser Doppler velocimetry (LDV) [37,50.138]. 

The application of laser Doppler velocimetry (LDV) to measure the electrophoretic mobility n of charged colloidal particles is known as laser Doppler electrophoresis (LDE). In a typical LDE experiment, an applied electric field drives the collective motion of charged colloidal particles. The particles pass through an interference pattern created by a dual-beam experimental setup (Section III.A.2). The collective electrophoretic velocity of the particles is then determined via intensity- or spectrum-based analysis of the scattered light, and the electrophoretic mobility n is calculated by dividing the velocity by the applied electric field strength. 

The laser phase Doppler particle analyzer (PDPA) simultaneously measures particle velocity, size and flux and may be considered an extension of laser Doppler velocimetry (LDV). It is particularly useful for... 

Principle of operation of laser Doppler velocimetry (LDV) instrument. (With permission... 

Dilute suspension - Particle-wall interaction predominates, interparticle spacing greater than 10 particle diameters. This is the normal range of laser Doppler velocimetry (LDV). Application is in conservative pneumatic conveying. 

Yang et al. (1992) also used the above mentioned probe in the measurement of particle velocity in a circulating fluidized bed. Experiments were carried out in a 140 mm i.d. bed with FCC particles at operating gas velocities ranging from 1.5 to 6.5m/s. As shown in Figure 4-26, it is worth mentioning that, in the dilute zone at 6.6 m axial position, the measured particle velocity agreed well with those measured by laser Doppler velocimetry (LDV). 

The conventional approaches to anemometry are laser Doppler velocimetry (LDV) and particle image velocimetry (PIV) [6,37,38]. The former is employed to obtain point-like measurements of one velocity component, whereas a combination of two or three LDV systems allows for the measurement of the vectorial structure of the velocities. The PIV is, instead, conceived for two-dimensional acquisition of velocity fields. One important industrial application of these techniques is in laser diagnostic of gas turbines and engines [9]. For instance, atomization of liquid fuels into droplets is typical of modern IC engines and one can study the fuel-air mixing that is an essential factor in efficient combustion. In... 

To compare the hydrodynamic behavior of supercritical CO2 and water, laser-Doppler velocimetry (LDV) measurements have been performed in a specially designed high-pressure mixing vessel provided with glass windows. For the same geometry. Computational Fluid Dynamics (CFD) calculations have been made for both media. 

Laser Doppler velocimetry (LDV) Laser Doppler velocity profile sensor Micro laser Doppler velocimetry (p-LDV)... 

In laser Doppler velocimetry (LDV) [1] based on the differential technique, two coherent laser beams, which are usually generated by beam splitting, are made to intersect at a small angle 26, see Fig. 1. In the area of intersection (the measurement volume), an interference fringe pattern with nearly parallel planes arises. The normal vector of these planes lies in the plane spanned by the LDV partial beams and is aligned... 

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