Environmental Engineering Reference
In-Depth Information
Figure 6.16
Formation of crystal and liquid structures of particles due to thermophoretic forces
which are created by the temperature gradient [109].
If two particles are located at a distance of less than 2
l
, the particle interaction
results from interaction of nonshielding particle charges at a given distance. These
charges are close to those for isolated particles if screening is determined by free
ions, because the main contribution to screening is from ion trajectories which
start outside the action of the other particle field. If screening is determined by
trapped ions, the current charge inside a sphere of a given radius is isotropic and
identical for an isolated particle and if another particle is present because ions
undergo many rotations around the particle in the course of their lifetime in a
close orbit. Thus, we have that the shielded charge of the particle in an ionized gas
on its interaction with another particle is close to or coincides with that of the other
particle. Next, the current charge
z
(
R
)atagivendistance
R
from it is determined
by (6.36) or (6.45) depending on the role of free and trapped ions in screening of the
particle field. These dependencies are closer to the stepwise distance dependence
for the current charge rather than to Debye or Yukawa dependencies. Therefore,
models based on the exponential dependencies of the distances between particles
do not describe the system of particles in an ionized gas.
