University of Minnesota
Aerospace Engineering and Mechanics
Fall 2002 Seminar Series



The effects of turbulence on nanoparticle growth


Prof. Sean C. Garrick

Dept. of Mechanical Engineering, University of Minnesota


Abstract

The formation of very fine particles from vapor encompasses a large number of physical/chemical phenomena.One must account for vapor phase chemistry, nucleation and subsequent growth (coagulation/coalescence). A key issue in dealing with the formation of nanoscale particles is agglomerates and chemical control. Soot particles, for example, are more often than not comprised of chains of nanoparticles. In the manufacture of nano-structured materials agglomeration can greatly affect the morphology and therefore quality. While a number of strategies have been attempted to minimize agglomeration, the exact mechanism for this behavior is still a complex interaction of time-temperature history along with molecular and macroscopic mixing. To better understand the effects of turbulence on nanoparticle coagulation a priori analysis of the subgrid particle-particle interactions during nanoparticle coagulation in temporal mixing layers is performed using direct numerical simulation data. The particle field is obtained by utilizing a sectional representation of the aerosol general dynamic equation. Several different Damkohler numbers representing the ratio of coagulation to convective time scales are considered. Comparisons between the total, filtered large-scale, and subgrid-scale (SGS) coagulation source term elucidates the effect of the unresolved SGS particle-particle interactions in performing large eddy simulations. Results indicate that at higher Damkohler numbers the effect of the SGS interactions is to increase the growth rate of the nanoparticles. Additionally, the effects of size-dependent or differential diffusion on particle growth is considered.

Biography

Obtained my PhD from the State University of New York at Buffalo in 1998. Joined the faculty of Mech. Engineering in the Fall of 1998. I teach courses in thermodynamics, heat transfer and computational fluid dynamics. Performs research in the areas of turbulent reacting flows and nanoparticle formation and growth.

Friday, December 6, 2002
209 Akerman Hall
2:30-3:30 p.m.


Refreshments served after the seminar in 227 Akerman Hall.
Disability accomodations provided upon request.
Contact Kristal Belisle, Senior Secretary, 625-8000.