The effects of orthokinetic collision, acoustic wake, and gravity on acoustic agglomeration of polydisperse aerosols

Dong, Shaozeng; Lipkens, Bart; Cameron, Timothy M.

doi:10.1016/j.jaerosci.2005.05.008

Cited by 88 publications

(50 citation statements)

References 8 publications

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“…However, the refill factor based on these mechanisms gives agglomeration rates several orders of magnitude lower than the experimentally observed rates [3,13,20]. Since the acoustic wake effect was revealed to play a significant role with micron-sized particles, some researchers [5,6,8,13,20] tried to use it as the major mechanism to explain the rapid refilling in acoustic agglomeration.…”

Section: Discussion Of the Computational Resultsmentioning

confidence: 99%

“…They concluded that small particles are pushed into the agglomeration volume by the adjacent large particles (see Figure 13(a)). Hoffmann [5] and Dong et al [6] used Dianov's analytical solution as the major refill mechanism. As mentioned before, this solution is limited for particles aligned along the direction of the sound wave, so in their studies small particles enter the Figure 13 Schematics of the refill mechanisms proposed by Tiwary and Reethof [13,20] (a), Hoffmann [5] and Dong et al [6] (b), and in this paper (c).…”

Section: Discussion Of the Computational Resultsmentioning

confidence: 99%

“…This volume is defined as the agglomeration volume. The mechanism of orthokinetic interaction was well summarized by Mednikov [3] and improved by other researchers [4][5][6]. Nevertheless, this mechanism cannot explain agglomeration of monodisperse aerosols or the way in which the agglomeration volume is refilled once it is emptied after one cycle.…”

mentioning

confidence: 99%

“…These mechanisms are generally considered to be the main acoustic agglomeration mechanisms for monodisperse aerosols because they are also active for same-sized particles [7]. Hydrodynamic mechanisms mainly include mutual radiation pressure and the acoustic wake effect [5,6,8,9]. The mutual radiation pressure is the effect due to the nonlinear interactions produced between the particle scattering wave and the incident field.…”

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confidence: 99%

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Numerical simulation of acoustic wake effect in acoustic agglomeration under Oseen flow condition

et al. 2012

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We numerically simulate the hydrodynamic interaction of aerosol particles due to the acoustic wake effect under the Oseen flow condition. Attraction is found for two nearby particles with an orientation angle of 0 to 50° with respect to the acoustic field, and weak repulsion is found outside this range. Good agreement is obtained between the numerical results and experiments in the literature. We study the influence of particle size, sound wave frequency and the particle separation. The result shows that the acoustic wake effect plays a significant role in acoustic agglomeration. It could be either the major agglomeration mechanism of monodisperse aerosols or the major refill mechanism for polydisperse aerosols to supplement orthokinetic interaction. Acoustic agglomeration is a process in which intense sound waves produce relative motions and collisions among aerosol particles. It can significantly shift the particle size distribution of an aerosol from smaller to larger sizes in a short time of the order of 1 s. Acoustic agglomeration has potential use in air pollution control as an aerosol preconditioning process to enhance the performance of conventional particle filtering devices, which are inefficient for retaining particles smaller than 2.5 m [1]. Acoustic agglomeration is governed by complex interaction mechanisms. The most significant ones are orthokinetic and hydrodynamic interactions [2]. Orthokinetic interaction is the most obvious mechanism. Particles with different sizes are entrained differently into the oscillating motion of the medium because of the differences in particle inertia. The relative motion leads to the approach and collision between particles. In one acoustic cycle, each larger particle sweeps a certain volume by its motion relative to smaller particles, and collects all the smaller particles in it. This volume is defined as the agglomeration volume. The mechanism of orthokinetic interaction was well summarized by Mednikov [3] and improved by other researchers [4][5][6]. Nevertheless, this mechanism cannot explain agglomeration of monodisperse aerosols or the way in which the agglomeration volume is refilled once it is emptied after one cycle.Hydrodynamic mechanisms are those which produce particle interactions through the surrounding medium because of hydrodynamic forces and the asymmetry of the flow field around the particle [1]. These mechanisms are generally considered to be the main acoustic agglomeration mechanisms for monodisperse aerosols because they are also active for same-sized particles [7]. Hydrodynamic mechanisms mainly include mutual radiation pressure and the acoustic wake effect [5,6,8,9]. The mutual radiation pressure is the effect due to the nonlinear interactions produced between the particle scattering wave and the incident field. However, so far, there is still no experiment to confirm this effect as a cause of agglomeration, and theoretical studies show that the mutual radiation pressure is much less important than the acoustic wake effect in acoustic agglome...

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Section: Discussion Of the Computational Resultsmentioning

confidence: 99%

Section: Discussion Of the Computational Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Numerical simulation of acoustic wake effect in acoustic agglomeration under Oseen flow condition

et al. 2012

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“…Acoustic agglomeration process has been widely studied (Mednikov, 1965;Dianov et al, 1968;Rosenberg, 1969;Dong et al, 2006;Sheng and Shen, 2007), but the development of this process toward industrial application has been slow. This is caused by the lack of suitable high intensity, high efficiency powerful sound sources and the corresponding full scale agglomeration equipment (GallegoJuarez et al, 1999).…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulation of Air Flow inside Acoustic Cyclone Separator

Vekteris

Strishka

Ozarovskis

et al. 2015

Aerosol Air Qual. Res.

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This paper presents a novel concept of cyclone separator, where sound waves are used to agglomerate fine particles. Sound waves generated by Hartmann acoustic generator are introduced into the secondary (core) air flow of cyclone separator. Results of numerical simulation of air flows inside conventional and acoustic cyclone separators are presented. It is shown that intensive pressure pulsations occur in acoustic generator's reflector. These pulsations generate an acoustic field. It is experimentally established that the average separation efficiency of conventional cyclone separator reaches 87.2% only, while separation efficiency of acoustic cyclone separator is approximately 97.5%. Obtained results show that air flows inside cyclone separator can be investigated numerically.

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Micro-droplet deposition and growth on a glass slide driven by acoustic agglomeration

Cao

Zhao

et al. 2021

Exp Fluids

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The effects of orthokinetic collision, acoustic wake, and gravity on acoustic agglomeration of polydisperse aerosols

Cited by 88 publications

References 8 publications

Numerical simulation of acoustic wake effect in acoustic agglomeration under Oseen flow condition

Numerical simulation of acoustic wake effect in acoustic agglomeration under Oseen flow condition

Numerical Simulation of Air Flow inside Acoustic Cyclone Separator

Micro-droplet deposition and growth on a glass slide driven by acoustic agglomeration

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