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Aerosol Kinetics
Equation of Motion
Consider an aerosol particle in a fluid flow as shown in figure 1. The
equation of motion of a sphericle aerosol particle of mass m
and diameter d is given as
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(1)
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Here up is the particle veolocity, uƒ is the
fluid veolocity, g is the acceleration
of gravity and the buoyancy effect in air is neglected. Here it is
assumed that the particle is away from walls and Stokes drag is assumed.
Dividing Equation 1 by  and rearranging, we find
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(2)
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where the particle response(relaxation)time is defined as
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(3)
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where  , ν is the kinematic
viscosity of the fluid and S = ρp/ρf is the
density ratio. In practice, for non-Brownian particles, Cc≈1 and
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(4)
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