The general dynamic equation for aerosols

Citation

Gelbard, Fred (1979) The general dynamic equation for aerosols. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/WJMB-2D76. https://resolver.caltech.edu/CaltechTHESIS:12112012-114024411

Abstract

This work focusses on developing and solving the conservation equations for a spatially homogeneous aerosol. We begin by developing the basic equations, and in doing so, a new form of the conservation equation or General Dynamic Equation (GDE), termed the discrete-continuous GDE, is presented. In this form, one has the ability to simulate aerosol dynamics in systems in which processes are occurring over a broad particle size spectrum, typical of those found in the atmosphere. All the necessary kinetic coefficients needed to solve the GDE are discussed and the mechanisms for gas-to-particle conversion are also elucidated.

Particle growth rates limited by gas phase diffusion, surface and volume reactions are discussed. In the absence of coagulation, analytic solutions for the above particle growth rates, arbitrary initial and boundary conditions, arbitrary sources, and first order removal mechanisms are developed.

To account for all processes, numerical solutions are required. Therefore, numerical techniques and the errors associated with the numerical solution of the GDE are discussed in detail. By comparing the numerical solution to both analytical solutions for simplified cases and smog chamber data, it is shown that the numerical techniques are highly accurate and efficient.

Techniques for simulating a sulfuric acid and water aerosol are presented. By application of the discrete-continuous GDE, the effect of neglecting cluster-cluster agglomeration, and the effect of a preexisting aerosol on the nucleation rate of a sulfuric acid and water aerosol are studied. The effects of coagulation are also elucidated by simulating the system with the full continuous GDE and the analytic solution to the continuous GDE in the absence of coagulation. Fairly good agreement between the predicted and experimentally observed distributions is obtained.

Finally, an exact solution to the continuous form of the GDE for a multicomponent aerosol for simplified cases is developed.

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