The general dynamic equation for aerosols
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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.