Aerospace Research - ISTC Funded Projects 1994-2009

In recent years, remote sounding of the
earth atmosphere in the millimeter radio
wave band has become widely used
with the purpose of determining spatial
distributions of its minor components.
Millimeter and submillimeter wave bands
meet the need for reliable, timely and
continuous monitoring of processes taking
place in the atmosphere, which is not
always possible in the optical range. In the
wave­number range 1 < ν < 20 cm ­1 , the
radiation absorption coefficient for water
vapor dimers is comparable to or even
in excess of the absorption coefficient
for monomers. The range 7 < ν < 8 cm ­1
appears to be especially promising, since
the dimeric absorption mechanism is in
this case in the atmospheric transparency
window. The radio­frequency radiation
absorption coefficient for water vapor
dimers in millimeter and submillimeter
bands is directly proportional to the
square of concentration of monomers,
whose content in engine exhaust jets is
considerably greater than in the ambient
atmosphere. Entrainment of combustion
products by vortices results in a noticeable
increase in the water vapor concentration
in them. With increasing water vapor
concentration, the absorption coefficient of
monomers grows linearly, but this growth is
little noticeable in the center of absorption
lines against the background of its initially
high level. In the atmospheric transparency
windows, where the dimeric absorption
mechanism dominates, a noticeable growth
of the absorption coefficient is observed
with increasing humidity. Thus, entrainment
of humid combustion products by aircraft
vortices makes them observable against
the background of the ambient atmosphere
due to formation of water vapor dimers in
the vortices.
In the course of Project implementation,
an algorithm was developed for computing
the number density of the simplest clusters
of water vapor (dimers, trimers, tetramers,
etc.) in atmospheric air. In developing this
algorithm, quantum­mechanical computations
Improvement of Safety and Operational Capacity
of the simplest cluster structure were used. The
number density of clusters is very sensitive to
temperature and pressure of the ambient
gas, which places stringent requirements on
gasdynamic simulation. It was found that the
clasterization process takes place in mixing
layers and near the axes of vortices, which
is consistent with the results obtained in the
framework of heterogeneous condensation
studies.
For additional formation of clusters, corona
discharge can be employed. This method
necessitates a study of formation of clusters
and microparticles being condensed on ions
generated in the flow by corona discharge.
In practice, such a discharge can be realized
in locations of vortex shedding (in the
neighborhood of the wingtips and flap edges).
It is supposed that such a system can be
created to simplify vortex visualization behind
a heavy aircraft.
A further step forward has been made in
developing the theory of droplets collision
speed, the linkage has been taken into account
between the characteristic time of turbulent
fluctuations and the Stokes relaxation of the
gas speed.
A simplified quasi­one­dimensional algorithm
(Q1D) was verified, which was able
to take into account a variety of chemical
reactions between impurities and to
determine their concentration at a distance
from the engine nozzle.
A complex numerical algorithm was also
developed which allowed taking into
consideration the growth of micron­size
droplets during their condensation and
coagulation.
Strength & Aeroelasticity investigations
The problem of statistically mean displacements
of an aircraft under the action of atmospheric
turbulence has been addressed. These studies
arose from the necessity to assess the initial
amplitude of oscillations of the vortices
forming behind a wing, and for this purpose,
amplitudes of oscillations of an aircraft center
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