Operating safety of a hot-shot wind tunnel with combined test gas heating in stabilization mode

In the present paper, we analyze emergency situations typical of short-duration wind tunnels with electric-arc or combined test-gas heating in the presence of stabilization and diaphragm-rupturing systems, which occur in the case of no discharge initiation in the settling chamber, with the capacitor battery having remained charged during the start of wind-tunnel systems. For avoiding such emergency situations, some additional changes based on using feedback elements are introduced into the wind-tunnel design: the piston of the fast-response valve is made hollow for increasing the volume of the shutoff cavity and for making the release of pressure from this cavity unnecessary; the high-pressure channel, which connects the piston and the piston rod with the settling-chamber cavity, is filled with a liquid and is closed from the side of the settling chamber with a piston; the device for controlled diaphragm breakdown is provided with an external electric circuit intended to control the diaphragm-rupturing process. Those modifications allow subsequent functioning of the wind-tunnel systems only in the presence of heat-supply-induced pressure growth in the settling chamber of the wind tunnel.     

Modelling of icing of flying vehicles in climatic wind tunnels

Various forms of icing of flying vehicles are considered. Dimensionless parameters of similarity are chosen and justified. The necessity of creating a climatic wind tunnel for modelling the icing processes is grounded. A possible structural scheme of the climatic wind tunnel is given. It seems reasonable to develop a small-scale test bench for testing methods aimed at generating a uniform field of concentrations of supercooled droplets of a given size and for identifying the efficiency of various anti-icing systems and coatings.     

Numerical simulation of the flow with a pseudo-shock in an axisymmetric expanding duct with a frontal inlet

The results of the numerical modeling of a flow with a pseudo-shock in an axisymmetric duct are presented. The duct included a frontal inlet with the initial funnel-shaped compression part and the cylindrical throat part as well as the subsequent expanding diffuser. To create a flow with a pseudo-shock, the duct was throttled with the use of the outlet converging insert. Numerical computations of the axisymmetric flow have been conducted on the basis of the solution of the Reynolds-averaged Navier?Stokes equations and with the use of the k-ω SST turbulence model. As a result of computations, such parameters of the flow were determined as the location of the beginning of the pseudo-shock, the length of its supersonic part, the velocity profiles in different cross sections of the pseudo-shock, the pressure distribution on the duct wall, the total pressure recovery factor, and others. The behavior of these parameters at the freestream Mach number М = 6 was analyzed versus the diffuser opening angle and different degree of the inlet duct throttling.     

Finiteness conditions for plane axisymmetric self-consistent motions of charged plasma electrons in a magnetic field

The plane axisymmetric self-consistent motions of electrons constituting a cylindrical beam is studied. The electrons move under the action of the electric field of uncompensated space self-charge against the background of plasma ions in the presence of a magnetic field. Conditions of electron movement finiteness for the given configuration of the electron beam are found.     

On the breakdown of axisymmetric smooth solutions for the 3-D Euler equations

We refine the Beale-Kato-Majda criterion for the breakdown of smooth solutions of the 3-D incompressible Euler equations in the case of axisymmetry. In this case the angular component of vorticity in the cylindrical coordinates alone controls blow-up of the higher Sobolev norms of the velocity.     

On the question of self-trapping of positrons in indium

The Doppler-broadening of the positron annihilation line in 5N indium has been studied over the temperature range 77 K to 427 K. No evidence for self-trapping has been discovered; rather, the prevacancy rise in the F-parameter appears linear. The best value for E_V is 0.59±0.03 eV.     

On a static axisymmetric solution of the Einstein equations

A family of static, axisymmetric, asymptotically flat solutions of the Einstein equations is discussed. A source with an exterior described by a member of this family initially could have an area smaller than that of a n appropriately defined Schwarzchild surface. Intuition does not suggest the fate of the collapsing source.     

On the question of the magnitude of day-night asymmetry for solar neutrinos

The effect of flavor day-night asymmetry is considered for solar neutrinos of energy about 1 MeV under the assumption that the electron-density distribution within the Earth is approximately piecewise continuous on the scale of the neutrino-oscillation length. In this approximation, the resulting asymmetry factor for beryllium neutrinos does not depend on the structure of the inner Earth’s layers or on the properties of the detector used. Its numerical estimate is on the order of ?4 × 10^?4, which is far beyond the reach of present-day experiments.     

Numerical study of the influence of flow blockage on the aerodynamic coefficients of models in low-speed wind tunnels

With the use of ANSYS Fluent software and ANSYS ICEM CFD calculation grid generator, the flows past a wing airfoil, an infinite cylinder, and 3D blunted bodies located in the open and closed test sections of low-speed wind tunnels were calculated. The mathematical model of the flows included the Reynolds equations and the SST model of turbulence. It was found that the ratios between the aerodynamic coefficients in the test section and in the free (unbounded) stream could be fairly well approximated with a piecewise-linear function of the blockage factor, whose value weakly depended on the angle of attack. The calculated data and data gained in the analysis of previously reported experimental studies proved to be in a good agreement. The impact of the extension of the closed test section on the airfoil lift force is analyzed.     

On certain new exact solutions of the Einstein equations for axisymmetric rotating fields

We investigate the Einstein field equations corresponding to the Weyl-Lewis-Papapetrou form for an axisymmetric rotating field by using the classical symmetry method. Using the invafiance group properties of the governing system of partial differential equations （PDEs） and admitting a Lie group of point transformations with commuting infinitesimal generators, we obtain exact solutions to the system of PDEs describing the Einstein field equations. Some appropriate canonical variables are characterized that transform the equations at hand to an equivalent system of ordinary differential equations and some physically important analytic solutions of field equations are constructed. Also, the class of axially symmetric solutions of Einstein field equations including the Papapetrou solution as a particular case has been found.     

On the question of the error in the partial capacitance method

An analytical method is proposed for calculating the capacitance of a planar capacitor constructed in the form of a two-layer structure. The method is used to calculate the capacitance of a planar capacitor containing a ferroelectric film. A number of calculations were performed to check the accuracy of the partial capacitance method. The calculations made it possible to determine the limits of accuracy of the partial capacitance method for a permissible calculational error of ±3%. Zh. Tekh. Fiz. 69, 8–13 (April 1999)     

On the question of nuclear track formation in plastic material

A review is given about nuclear track formation in plastic track detectors. The radiation damage of heavy ions around the latent tracks is studied using measurements of radial track etch rates in Å-dimensions.