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Measurement of the Influence of Directed Particle motion on the turbulent particle deposition velocity by means of laser‐doppler anemometry
Author(s) -
Holländer Werner,
Pohlmann Gerhard
Publication year - 1991
Publication title -
particle and particle systems characterization
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.877
H-Index - 56
eISSN - 1521-4117
pISSN - 0934-0866
DOI - 10.1002/ppsc.19910080104
Subject(s) - deposition (geology) , particle (ecology) , turbulence , mechanics , brownian motion , chemistry , thermophoresis , diffusion , particle deposition , doppler effect , classical mechanics , electric field , physics , optics , thermodynamics , geology , nanofluid , paleontology , heat transfer , oceanography , quantum mechanics , sediment , astronomy
The dry deposition of particles from the atmosphere is not well understood for reasons of surface variabilities and mutual interactions between surface and particles. However, even relatively simple influences of physical parameters have so far resisted successful parameterization, although some progress has been achieved. There is no general way to determine the relative contributions of stochastic turbulent and Brownian diffusion and directed motions (i. e. sedimentation) to the total deposition velocity since they contribute in a nonlinear manner to the total deposition velocity. The directed motion is an unknown function of atmospheric turbulence, the particle diffusion coefficient D p and the sum of all directed particle motions by thermophoresis, diffusiophoresis, photophoresis, electrophoresis, sedimentation etc. Practically nothing is known about the action of the first three forces and even the easily accessible electrophoresis has not been considered relevant for deposition of atmospheric particles. Because it is relatively easy to change an electric field with all other parameters kept constant and measure the absolute difference in total deposition velocity the following experimental Laser‐Doppler study was intended to show the feasibility of the field‐changing‐technique and the magnitude of the effects without quantitatively determining the electrical mobility distribution as a function of particle size.