Nonstationary flow in a channel with variable cross section under conditions of periodic pulsed energy supply

The effect of a periodic pulsed supply of energy, equal to that of hydrogen combustion in air, on the structure of a supersonic flow in a channel of variable cross section modeling a ramjet tract has been studied. The flow has been numerically simulated based on two-dimensional gasdynamic equations. Various flow regimes are obtained depending on the configuration of energy supply zones and the excess air ratio in the channel.     

Intensification of mixing of parallel compressible flows using a localized pulse-periodic energy supply

The possibility of intensification of the mixing of supersonic and subsonic low-density gas jets that interact with an oblique shock with an ambient cocurrent supersonic flow using a localized pulse-periodic energy supply is demonstrated by means of numerical simulation. It is shown how an energy source located in front of the shock at the jet axis and also in an external flow affects the generation of large-scale vortex structures that favor the mixing process intensification.     

The effect of localized pulse-periodic energy supply on supersonic mixing in channels

Results of numerical simulations of supersonic flows in flat channels with narrowing and expanding input sections confirm the possibility of intensification of the mixing of a low-density supersonic gas jet with surrounding co-current flow by means of a localized pulse-periodic energy supply. The influence of the positions of the jet and energy-supply source on the formation of large-scale vortex structures favoring the intensification of mixing is demonstrated.     

Two-mode model of flow in a plasmotron channel

The characteristics of an electric arc in a turbulent gas flow are calculated on the basis of the concept of laminar flow in the arc zone.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 51, No. 5, pp. 830–835, November, 1986.     

The condition of steady-state flow in a channel of variable cross section in the presence of heat supply and kinetic energy dissipation

An expression for maximum permissible entropy gain is obtained and the condition of passage via the velocity of sound is found for the steady-state flow of an ideal gas in a channel of variable cross section in the presence of heat supply and kinetic energy dissipation. Particular flow examples are considered.     

Shock-wave flow regimes at entry into the diffuser of a hypersonic ramjet engine: Influence of physical properties of the gas medium

The physical aspects of the effective-adiabatic-exponent model making it possible to decompose the total problem on modeling of high-velocity gas flows into individual subproblems (“physicochemical processes” and “ aeromechanics”), which ensures the creation of a universal and efficient computer complex divided into a number of independent units, have been analyzed. Shock-wave structures appearing at entry into the duct of a hypersonic aircraft have been investigated based on this methodology, and the influence of the physical properties of the gas medium in a wide range of variations of the effective adiabatic exponent has been studied. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 4, pp. 69–80, July–August, 2006.     

Fluctuation model of a nonequilibrium two-phase channel flow

An ill-posed Cauchy problem for a model of a nonequilibrium two-phase flow in the barotropic approximation is transformed into a well-posed problem by changing the type of the initial hyperbolic equations. Approximation of fluctuations of the phase velocities by a random delta-correlated process and averaging of the equations over its realizations generate a system of parabolic equations. Results of numerical integration of this system are compared with experiment and calculations by well-known models.Notation a velocity of propagation of acoustic perturbations - frozen velocity of sound - b dimensionless constant - h enthalpy - L tube length, scale of velocity fluctuations - p pressure - R complex - T temperature - t time - velocity - x coordinate - step of the difference scheme - fluctuating component of the velocity, delta-function - dimensionless variable - phase density - ² variance of the velocity - characteristic correlation time - volume phase concentration Institute of Engineering Thermophysics, Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 66, No. 6, pp. 651–656, June, 1994.     

Nonstationary concentration polarization in laminar ultrafiltration in a plane channel

A semiintegral method of determination of concerntration polarization is suggested and specific features of the latter in laminar ultrafiltration in a plane channel are discussed.Academic Scientific Complex A. V. Luikov Heat and Mass Transfer Institute, Academy of Sciences of Belarus, Minsk. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 67, Nos. 1–2, pp. 103–107, July–August, 1994.     

Supersonic flow regimes with a pulsating laser radiation energy supply

A comparative analysis of the gas flow regimes behind the region of laser energy supply to a supersonic jet is performed depending on the laser radiation focusing conditions. A relationship established between the energy and gasdynamic parameters reveals a significant difference in the flow parameters (velocity, stagnation pressure) behind the extended and localized (point) thermal plasma sources for the identical initial conditions in a supersonic jet with the Mach numbers M=1.5–10.     

Formation of quasisteady supersonic flow with a pulse-periodic plasma heat source

An analysis is made of experimental data on the influence of a pulse-periodic optical discharge in a supersonic argon stream on the aerodynamic drag of streamlined objects. The interrelation established between the parameters of the laser radiation and the stream is used to determine the threshold frequency of the laser pulses which determines the transition to quasi-steady-state flow. Pis’ma Zh. Tekh. Fiz. 24, 8–13 (August 26, 1998)     

Impurity dispersion in the turner model for flow in a porous channel

A one-dimensional model for longitudinal diffusion in a capillary with an immobile layer is derived.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 27, No. 1, pp. 92–96, July, 1974.     

Boundary layer separation in a laminar supersonic flow with energy supply source

The influence of electric discharge in a supersonic gas flow on the separation of a laminar boundary layer has been studied by numerical methods. The discharge is modeled by an energy supply source with preset intensity and configuration. It is established that the behavior of flows in the system with thermally insulated and isothermally cooled walls differs in a broad range of the heat source power. The possibility of controlling the boundary layer separation is demonstrated.     

A model of liquid flow in a channel with elastic walls

It is suggested to describe a liquid flow in a cylindrical round channel with elastic walls in terms of a two-fluid model used to describe the flow of He II in narrow capillaries near absolute zero. The idea is based on a similar (phonon-like) shape of the spectrum of elementary excitations at small wavenumbers k. The calculations show that the density ρ_n of a normal (i.e., viscous) liquid component (water in a steel tube) at 300 K is about 50 times smaller than the total density. This explains the paradox related to flow in a round tube for which anomalously large Reynolds numbers (Re∼10⁵) are observed. Since Re∼ρ_n, real Reynolds numbers must also be about 50 times as small, that is, on the same order of magnitude as those for a flow between planes under otherwise equal conditions. A physical reason for the appearance of superfluidity at high (∼300 K) temperatures is a decrease in repulsion between small density fluctuations in the liquid, which is related to their interaction being screened by elastic waves in the channel walls.     

Nonstationary radiation-gasdynamic model of a laser-plasma accelerator

Based on the system of two-dimensional axisymmetrical continuity equations, Navier-Stokes and energy equations, and the equations of selective heat radiation transfer, a computational model is constructed and conditions of unsteady subsonic flows in a cylindrical channel of a power unit of the laser-plasma accelerator type are investigated. The governing parameters of the model are calculated, at which numerical solutions can be obtained to describe steady laminar gas flow in the neighborhood of the region of heat release, nonstationary oscillatory motions, and nonstationary vortex motion. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 1, pp. 174–179, January–February, 2000.     

Nonstationary velocity pulsations in turbulent flow

It is experimentally established that the velocity pulsations in a developed turbulent flow in a pipe at small Reynolds numbers are statistically nonstationaryTranslated from Inzhenerno-Fizicheskii Zhurnal, Vol. 42, No. 3, pp. 392–395, March, 1982.     

A statistical model of the longitudinal dispersion process in turbulent flow in a channel

Summary The important practical problem of the dispersion of a passive contaminant in a fluid flowing through a pipe or channel of uniform cross-section is usually analysed in terms of the distribution of concentration. In this paper however a different though approximate approach is adopted which both illustrates the essential statistical nature of the process and may be quicker to employ when approximate answers are acceptable in a practical problem. A simple statistical model is proposed for the motion of a single molecule of contaminant and leads to an expression for the covariance of the velocity of the molecule in terms of the fluid velocity, and hence to a value of Taylor's longitudinal diffusivity. The model is applied to two simple flows in a channel, one of which illustrates the effect of the viscous sub-layer. Despite the number of simplifying assumptions made in constructing the model it gives results which are close to those obtained by conventional means. Ways in which the model could be adapted to give even better results are discussed.     

Nonstationary flow of solutions of flexible-chain polymers in a porous medium

Aqueous solutions of polyethylene oxide have been studied under the conditions of nonstationary longitudinal flow. The investigations have confirmed the deviations from Darcy’s law according to the mechanism the basis for which is provided by the concepts of a strong strain action of the hydrodynamic field on coiled macromolecules. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 5, pp. 123–127, September–October, 2005.