Brownian coagulation of aerosol particles by Monte Carlo simulation

Nowakowski, B.; Sitarski, Marek

doi:10.1016/0021-9797(81)90356-8

Cited by 19 publications

(10 citation statements)

References 14 publications

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“…Earlier studies of transition regime collisions via Langevin simulations suffered from high statistical variability in the obtained results or made use of a limited number of calculated values (Nowakowski and Sitarski 1981;Narsimhan and Ruckenstein 1985;Gutsch et al 1995). Due to the small time steps used in calculations as well as the strict convergence criteria employed, the results obtained in this study do not suffer from the same degree statistical variability as prior work (though some random variations in results from Brownian Dynamics are inevitable).…”

Section: Comparison To Existing Kernelsmentioning

confidence: 85%

“…A number of previous studies have used the Langevin equation to examine transition regime collisions (Nowakowski and Sitarski 1981;Gutsch et al 1995;Trzeciak et al 2004;Heine and Pratsinis 2007;Isella and Drossinos 2010). For our calculations, we build upon the methods of Narsimhan and Ruckenstein (1985), who were the first to note that in examining dilute systems, only the motion of two colliding entities need to be considered, as opposed to a large multientity computational domain.…”

Section: Simulation Proceduresmentioning

confidence: 99%

“…Nonetheless, there are several reasons for further examination of the transition regime collision kernel. First, collision kernel expressions have been sparingly compared with results of Brownian dynamics simulations (Trzeciak et al 2004;Madler et al 2006;Heine and Pratsinis 2007), and when comparison has been performed (Nowakowski and Sitarski 1981;Narsimhan and Ruckenstein 1985), it has been limited to collisions between identical-sized particles or led to poor agreement with the unambiguous free molecular and continuum limiting expressions (Gutsch et al 1995). With recent advances in computational capabilities, Brownian dynamics simulations can accurately predict thermally driven particle-particle collision rates (the Z → ∞ limit); hence, they should be able to provide a means for more detailed examination of collision kernel expressions than is possible with currently available experimental approaches.…”

Section: Introductionmentioning

confidence: 99%

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Determination of the Transition Regime Collision Kernel from Mean First Passage Times

Gopalakrishnan

Hogan

2011

Aerosol Science and Technology

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Particle-vapor molecule (condensation) and particle-particle (coagulation) collision kernels are critically important parameters for the description of particle size distribution evolution in aerosols. We use mean first passage time calculations to find a dimensionless form of the collision kernel that applies in the limit where the ratio of the masses of colliding entities (aerosol particles or vapor molecules) to gas molecule mass, Z, approaches infinity, and the colliding entities are dilute in concentration. In these calculations, the motion of colliding entities is monitored with Langevin dynamics, and the collision kernel is inferred from the time required for collision. The presented analysis reveals that the dimensionless collisional kernel (H) is a function solely of the diffusive Knudsen number (Kn D , the square root of the product of kT and the reduced mass divided by the product of the reduced friction factor and collision radius), and a number of commonly used expressions for the collision kernel also collapse to the functional form H(Kn D ), irrespective of whether they were derived for Z → ∞ or Z → 0 conditions. The examined collision kernel expressions are further found to agree within 10% of our calculations as well as with each other across the entire Kn D range. This result suggests that a single collision kernel can be used to describe all transition regime collision rates, i.e., both condensation and coagulation rates, with reasonable accuracy, and establishes that Langevin-equationbased mean first passage time calculations can serve as a simple approach to examine transition regime collision phenomena.

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Section: Comparison To Existing Kernelsmentioning

confidence: 85%

Section: Simulation Proceduresmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Determination of the Transition Regime Collision Kernel from Mean First Passage Times

Gopalakrishnan

Hogan

2011

Aerosol Science and Technology

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“…In contrast with the recent work of Nowakowski & Sitarski (1981), the particles studied here are much larger than the molecular free path in the fluid, and so are in the continuum regime of Brownian motion. Also the time step llt of the simulation is very much larger than the particle viscous relaxation time tr = 2r 2 j9v.…”

Section: Brownian Motionmentioning

confidence: 72%

Monte Carlo simulation of coagulation in discrete particle-size distributions. Part 1. Brownian motion and fluid shearing

1984

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A method for the Monte Carlo simulation, by digital computer, of the evolution of a colliding and coagulating population of suspended particles is described. Collision mechanisms studied both separately and in combination are: Brownian motion of the particles, and laminar and isotropic turbulent shearing motions of the suspending fluid. Steady-state distributions are obtained by adding unit-size particles at a constant rate and removing all particles once they reach a preset maximum volume. The resulting size distributions are found to agree with those obtained by dimensional analysis (Hunt 1982).

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“…While Langevin dynamics simulations have been used in the past to describe aggregation in the free molecular regime (Nowakowski and Sitarski 1981;Mountain et al 1986;Mulholland et al 1988; Ranganathan and Hogan 2011), they are computationally expensive. We have developed a MonteCarlo (MC) method for the crossover study similar to ones used in the past for continuum regimes (Pierce et al 2006;Heinson et al 2010).…”

Section: Simulation Methodsmentioning

confidence: 99%

Crossover from Ballistic to Epstein Diffusion in the Free-Molecular Regime

Heinson

Pierce

Sorensen

2014

Aerosol Science and Technology

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We investigate, through simulation, a system of aggregating particles in the free molecular regime that undergoes a crossover from ballistic to diffusive motion. As the aggregates grow, the aggregate mean free path becomes smaller and the motion between collisions becomes more diffusive. From growth kinetics, we find that when the ratio of the aggregate mean path to the mean aggregate nearest neighbor separation reaches of the order of unity, a crossover to diffusive motion occurs. This ratio, called the nearest neighbor Knudsen number, becomes an important parameter in understanding aerosol aggregation in the free molecular regime.

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Brownian coagulation of aerosol particles by Monte Carlo simulation

Cited by 19 publications

References 14 publications

Determination of the Transition Regime Collision Kernel from Mean First Passage Times

Determination of the Transition Regime Collision Kernel from Mean First Passage Times

Monte Carlo simulation of coagulation in discrete particle-size distributions. Part 1. Brownian motion and fluid shearing

Crossover from Ballistic to Epstein Diffusion in the Free-Molecular Regime

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