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Mitigation of preferential concentration of small inertial particles in stationary isotropic turbulence using electrical and gravitational body forces.

Karnik, Aditya U.; Shrimpton, John S.

Authors

Aditya U. Karnik

John S. Shrimpton



Abstract

Particles with a certain range of Stokes numbers preferentially concentrate due to action of turbulent motion and body forces such as gravity are known to influence this process. The effect of electric charge, residing on particles, upon the phenomenon of preferential concentration is investigated. We use direct numerical simulations of one-way coupled stationary isotropic turbulence over a range of particle Stokes numbers, fluid Taylor Reynolds numbers, and electrical and gravitational particle body force magnitudes, the latter characterized by non-dimensional settling velocities, v*c and v*g, respectively. In contrast to the gravitational body force, the electrical analogue, acting on an electrically charged particle, is generated by an electric field, which is in turn a function of the degree of preferential concentration. Thus, the electrical body force is created by, and mitigates, preferential concentration. In the absence of gravity, it is estimated that v*c ≈ 1.0 is sufficient to homogenise a preferentially concentrated particle distribution. It is seen that charging drastically reduces the radial distribution function values at Kolmogorov scale separations, which gravitational force does not. This implies that charging the particles is an efficient means to destroy small clusters of particles. On incorporating the gravitational force, the amount of charge required to homogenise the particle distribution is reduced. It is estimated that v*c ≈ 0.6 is sufficient to homogenise particle distribution at v*g = 2.0. This estimation is corroborated by several different indicators of preferential concentration, and the results also agree reasonably well with corresponding experiments reported in literature. Calculations also suggest that sprays generated by practical charge injection atomizers would benefit from this electrical dispersion effect.

Journal Article Type Article
Publication Date Jul 31, 2012
Journal Physics of Fluids
Print ISSN 1070-6631
Electronic ISSN 1089-7666
Publisher AIP Publishing
Peer Reviewed Peer Reviewed
Volume 24
Issue 7
Pages 073301
Institution Citation KARNIK, A.U. and SHRIMPTON, J.S. 2012. Mitigation of preferential concentration of small inertial particles in stationary isotropic turbulence using electrical and gravitational body forces. Physics of fluids [online], 24(7), article ID 073301. Available from: https://doi.org/10.1063/1.4732540
DOI https://doi.org/10.1063/1.4732540
Keywords Combustion; Stochastic processes; Gravitational force; Particle distributions; Eddies; Fluid jets; Classical statistical mechanics; Turbulent flows; Electrical properties and parameters; Electrostatics

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