Particle size phase Doppler anemometry

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

Phase Doppler anemometry is a specialised research technique which gives information on both particle size and velocity of single particles within the cloud. 

A method which has received considerable attention over the past 15 years is phase-Doppler anemometry (PDA) which allows determination of the size of spherical particles, droplets or bubbles. Hence, local particle size distributions and size-velocity correlations can be obtained. Moreover, recent developments provide the basis for accurate particle concentration or mass flux measurements... 

The principle of phase-Doppler anemometry (PDA) relies on the Doppler difference method used for conventional laser-Doppler anemometry and was first introduced by Durst and Zare (1975). By using an extended receiving optical system with two or more photodetectors it is possible to measure simultaneously size and velocity of spherical particles. For obtaining the particle size the phase shift of the light scattered by refraction or reflection from the two intersecting laser beams is used. 

Qiu, H.-H. and Sommerfeld, M., A reliable method for determining the measurement volume size and particle mass fluxes using phase-Doppler anemometry. Experiments in Fluids, Vol. 13, 393-404 (1992)... 

Various flow visualisation techniques have been utilised to obtain experimental results from local gas hold-ups and bubble size distributions (BSD) in a gas-liquid mixed tank. Particle Image Velocimetry (PIV), Phase Doppler Anemometry (PDA), Capillary suction probe (CSP), High-speed video imaging (HSVI) and Electrical Resistance Tomography (ERT) techniques have been applied. The applicability of various techniques is dependent on the location of the measurement, the physical properties of the gas-liquid flow, the gas hold-up and the size of the tank. 

Pig. 13.5 Determination of particle size in Phase Doppler Anemometry (PDA). The phase difference between two Doppler bursts is computed from A4> = 2 K(AtlT). The figure is drawn based on a sinular sketch from Manasse et al. [126]... 

Phase Doppler anemometry (PDA) is a technique akin to LDA. In PDA the laser light scattered in the measuring volume by a particle is detected at two angles, making it possible to gain information not only about the velocity of a particle but also its size. Mothes and Loffler (1985) report a study wherein they used this technique to gain information about the distribution of particle sizes within the body of a gas cyclone. 

Phase Doppler anemometry or phase Doppler analysis was proposed two decades ago, based on the then well-established flow measurement technology-laser Doppler velocimetry [110]. PDA is widely used in sizing spherical and homogeneous particles, such as liquid sprays, aerosols, air bubbles in liquid, or other spherical particles. When single particles move through the intersection of at least two focused laser beams, they scatter light from each beam with different individual Doppler frequency shifts. Multiple detectors are placed at... 

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