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A new class of exact solutions with
functional arbitrariness describing the
motion of a polytropic gas is
constructed on the basis of invariant
submodels of rank two of the
evolutionary type. In the solutions
obtained, the velocity is a linear
function of some spatial coordinates.
These solutions describe continuous gas
dispersion and the motion with density
collapse at a finite time.

The paper studies theoretically and
experimentally hydrodynamic loads that
act on horizontally placed cylinders of
rhombic and square cross sections,
oscillating harmonically in a linearly
stratified fluid. An analytical solution
is found with the use of affine
similitude. Hydrodynamic force
coefficients were evaluated
experimentally from Fourier transforms
of records of damped oscillations in a
time

A boundary-value problem is posed to
determine the wave  motion caused by
propagation of a gravity wave on the
free surface of a layer of a two-phase
medium. The problem is solved
analytically in the linear
approximation. The shape of the free
surface, the phase velocity, and the
frequency and damping factor of the wave
are determined. An example of the
solution of the problem is given.

Interaction of a shock wave and a
motionless combined discontinuity
separating two two-component mixtures
with different initial volume
concentrations is studied on the basis
of numerical simulation of unsteady
processes. The calculations were
performed using a modified method of
"coarse particles" and a high-accuracy
TVD difference scheme adapted to
calculation of two-phase flows. Flow
parameters determined by analytical
dependences coincide with those obtained
by numerical simulation at large times
of the process. Upon interaction of the
shock wave and the combined
discontinuity, the type of the transient
or reflected shock wave may coincide
with or differ from the type of the
incident shock wave. The possibility of
existence of a pressure difference at
the combined discontinuity boundary,
which was earlier predicted
analytically, is confirmed.

The effect of a texture transition and selective reflection in cholesteric liquid crystals was applied for a study of structure of near-wall flow in a channel. For the range of Re_Dh from 1.8^. 10³ to 18^. 10³, the method of liquid-crystal thermography was applied for research of heat transfer and flow structure on a model of heat exchanger at different angles between the main stream and the rib direction. The empirical relationships for integral number Nu with number Re and heat exchanger geometry are presented.

Stability of the structure of emulsion formed by oil drops suspended in an alcohol-water solution of an identical density under the action of a local heat pulse is experimentally studied. Stability of the emulsion structure characterized by the distribution of the numerical concentration of drops over the medium volume is considered within a time period where the interaction (mutual attraction) of drops with a given initial volume concentration may be neglected. As a result, a condition was determined according to which the emulsion structure is stable if the product of the amount of heat brought to the medium by the local heat pulse and the heat-pulse duration does not exceed some value, which is constant for a given liquid.

The method for more accurate definition of the form equations of state was proposed on the basis of thermodynamic analysis. This statement was checked on the example of several equations of state: van der Waals and Redlich

It is shown for ideal gas considered within the framework of a continual mathematical model that the quantities accepted as the heat flux density often do not correspond to the conditions necessary for such a status. In this connection, the procedure for choosing a quantity accepted as the heat flux density is refined and corrected. The commonly accepted assumptions on the driving forces of the diffusion of medium components are corrected respectively. It is shown that neither the gradients of chemical potentials of the gas molecular components nor of their ratios to temperature are the driving forces for the diffusion transport of component masses relative to medium motion with mean mass velocity but the quantities - Grad[(R/_i)lnp_i], where pi is the partial pressure of the i-th molecular component of gas, _i is its mole mass. The assumption is stated on the existence of such a type of the diffusion fluxes densities of components, to which the Onsager coefficients equal to zero of the mutual influence between the heat flux and diffusion fluxes correspond. The relations are obtained between the coefficients of multicomponent mutual diffusion and thermal diffusion ratios, which correspond to two variants of assumption realization.

A multi-channeled high-voltage pulse generator is designed intended for spark-discharge visualization and measurement of gas flow velocity in wind tunnel facilities. The conditions for spark-discharge ignition both in a uniform and sharply non-uniform velocity field are established. A two-pulsed spark-discharge ignition regime is realized, which allows to enlarge the controlled gas-flow zone by a factor of 2   3. The minimum amplitude of a voltage pulse for obtaining a second spark discharge and the maximum time interval appropriate for tracing the initial spark are determined. A description of practical implementation of the spark-tracing method in a supersonic gas jet is given. Results of direct flow-velocity measurements in a short-duration wind tunnel facility are reported.

The electric and luminous characteristics of low-frequency inductive discharge of transformer type (IDTT) in mercury vapor were studied experimentally for different parameters of the discharge: mercury vapor pressure in the discharge chamber and the input power of the discharge. The energy distribution over the spectral range of 250 - 600 nm and volt-ampere characteristics were measured for the following discharge parameters: power 2 - 100 kW (specific power 10 - 500 W/cm), mercury vapor pressure 2 - 40 kPa. The IDTT characteristics were analysed using a U-like channel model for axisymmetric thermal arcs; the results were compared with characteristics for regular arc discharge in mercury vapor. The dependency of key electric and luminous characteristics of IDTT on the discharge parameters is very close to those for mercury arc discharge.