Tl. Hoffmann et Gh. Koopmann, VISUALIZATION OF ACOUSTIC PARTICLE INTERACTION AND AGGLOMERATION - THEORY EVALUATION, The Journal of the Acoustical Society of America, 101(6), 1997, pp. 3421-3429
In this paper experimentally observed trajectories of particles underg
oing acoustically induced interaction and agglomeration processes are
compared to and validated with numerically generated trajectories base
d on existing agglomeration theories. Models for orthokinetic, scatter
ing, mutual radiation pressure, and hydrodynamic particle interaction
are considered in the analysis. The characteristic features of the cla
ssical orthokinetic agglomeration hypothesis, such as collision proces
ses and agglomerations due to the relative entrainment motion, are not
observed in the digital images. The measured entrainment rates of the
particles are found to be consistently lower than the theoretically p
redicted values. Some of the experiments reveal certain characteristic
s which may possibly be related to mutual scattering interaction. The
study's most significant discovery is the so-called tuning fork agglom
eration [T. L. Hoffmann and G. H. Koopmann, J. Acoust. Sec. Am. 99, 21
30-2141 (1996)]. It is shown that this phenomenon contradicts the theo
ries for mutual scattering interaction and mutual radiation pressure i
nteraction, but agrees with the acoustic wake effect model in its intr
insic feature of attraction between particles aligned along the acoust
ic axis. A model by Dianov et al. [Sov. Phys. Acoust. 13 (3), 314-319
(1968)] is used to describe this effect based on asymmetric flow field
s around particles under Oseen flow conditions. It is concluded that t
his model is consistent with the general characteristics of the tuning
fork agglomerations, but lacks certain refinements with respect to ac
curate quantification of the effect. (C) 1997 Acoustical Society of Am
erica.