Home – Home – Jornals – Thermophysics and Aeromechanics 2005 number 4

The paper statistically treats nanoparticle transport processes in gases and liquids. We show that nanoparticle transport in rarefied gases can be predicted based on the Boltzman kinetic equations involving a special interaction potential of carrier-gas molecules with the particle. Data on nanoparticle diffusivity versus nanoparticle size and solvent temperature are presented. Mechanisms of nanoparticle relaxation in dense gases and liquids are described. It is shown that the main nanoparticle relaxation mechanism in liquids is the interaction of nanoparticles with microfluctuations of solvent velocity and density fields. For the first time, data on the interaction forces acting on nanoparticles in gases and liquids are reported.

We present the results of experimental and numerical studies of different gas-dynamic protectors developed to decrease the back flows of contaminating fractions at orientation thrusters of the spacecraft.

The results of numerical investigations of the streamwise vortex interaction with an oblique shock whose flow inclination angle b = 23.3

Experimental results are presented on transformation of a solitary L-structure into a turbulent spot and control of this process by means of riblets on the wetted surface in the boundary layer on a flat plate. It is shown that riblets exert a stabilizing effect on transformation of the L-structure into a turbulent spot. The L-structure on a smooth surface is shown to stretch in the streamwise direction and transform into a hairpin vortex, which becomes a turbulent spot further downstream. The intensity of the L-structure on riblets first increases and then decays further downstream, reaching less than half its value on a smooth surface. Finally, the L-structure decays on riblets without forming a turbulent spot.

A joint testing of the specialized (VP2/3) and universal (FLUENT) packages of the applied programs of hydrodynamic and thermophysic structure is carried out on the basis of the solution of a known benchmark test on recirculating flow of a viscous incompressible fluid in a square lid-driven cavity. The Reynolds-averaged Navier

An analytic solution is found for a boundary-value problem of vortex motion of viscous gas in the cylinder of an internal combustion engine (ICE) with flat piston geometry at the compression stroke. An analytic solution has been determined for the angular velocity component in a cylindrical coordinate system with a refining polynomial, which reduces to a system of nonlinear algebraic equations after its substitution into the model equation, the initial and several boundary conditions. By virtue of the uniqueness of the solution of the boundary-value problem under study, the angular velocity component is found from the obtained values of the constants of the refining polynomial at a given point of the internal cylinder space. The obtained solution is compared with experimental data.

The method was developed for calculation of incompressible fluid flow through a short vortex chamber with hyperbola-shaped walls. Calculations are close to experimental data. Properties of flows are compared in chambers with hyperbolic and flat walls. In a chamber with hyperbolic walls the effect of friction on the flow is found to be stronger than for a flat-wall analog.

The results of mathematical modelling of aerodynamic thermal processes in the rooms are presented for several schemes of the air supply and removal. The model rooms having the shape of a cube are considered, inside which there are or there are no obstacles and heat sources. The equations of a steady three-dimensional isothermal or non-isothermal gas motion corresponding to the k-ε- turbulence model are used to describe the thermal and aerodynamic processes. The similarity criteria are found for the processes of the heat and air exchange. Basing on them, a detailed numerical investigation of the influence of determining parameters of the problem on the local and averaged characteristics of the velocity and temperature fields has been carried out.

Results of investigating a co-current bubbly downflow in a vertical tube of the 20-mm inner diameter are presented. The two-phase flow was formed using a special mixer, which allows variation of gas bubble sizes. Void fraction, liquid phase velocity and its pulsation were measured by the electrochemical method. In comparison with a single-phase flow, it was noted that turbulent pulsations of liquid velocity in the two-phase flow are considerably suppressed. A significant effect of dispersed composition of a gas phase on average and pulsation flow characteristics was demonstrated.

Gashydrate formation in a gas- and water-saturated reservoir due to gas injection into the bed is examined. Self-similar solutions to the planar one-dimensional problem are constructed, which give the distribution of main bed characteristics. It is found that, depending on injected-gas parameters, the gashydrate forms either at a frontal surface or in an extended region.

The problem of matching the non-isothermal models of Muskat

Phase transitions in binary borate systems were studied by the oscillation method of phase analysis; thermodynamic properties of melts were calculated. Measurements were carried out for several systems: Li₂O-B₂O₃, Na₂O-B₂O₃, K₂O-B₂O₃, Rb₂O-B₂O₃, Cs₂O-B₂O₃, and BaO-B₂O₃. abstract_eng||The melting temperature was measured accurately, and the types of melt-ing for the systems were specified. The composition of crystallized phase and compounds depends on the thermal prehistrory of samples. The melt viscosity was estimated for all systems. For binary systems in the framework of subregular solution we calculated thermodynamic properties of melts and enthalpy for compounds with congruent melting. There exists a correlation between the dissociation degree of a compound and the melt supercooling before the spontaneous.

Results of experiments with thermochemical cathodes made on the basis of hafnium and zirconium are presented. Data on heat fluxes to an electrode and its erosion depending on the arc current allowed an estimate of the service life of hafnium cathode in oxygen-bearing media. The scheme of cathode with four thermoemission insertions was suggested and implemented for a significant prolongation of cathode operation in comparison with a single-insertion cathode.

Experiments were carried out with a two-tier Savonius rotor with optimal proportions of geometry parameters. The testing was performed in a tow basin with almost zero effect of flow boundaries. The positive net power is generated for the specific speed varying from zero to one, and the maximum of the wind energy utilization coefficient is 20 %.