Hydrodynamic instability of the contact zone between accelerated gases

An experimental apparatus for investigating Rayleigh-Taylor instability in the transition layer between two gases at accelerations g 10⁵g₀ (g₀ is the acceleration of gravity) is described. The constantly acting acceleration is communicated to the contact zone by the compression wave formed ahead of a flame front. The linear stage of development is investigated together with the effect of the thickness of the contact zone. It is shown that on the interval 0.3 < <- ( is the wavelength of the disturbance at the edge of the contact zone) the rate of growth of the perturbation amplitude 0.5₀, where ₀ is the amplitude growth rate for media separated by an interface with a discontinuous change of density.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 15–21, November–December, 1991.     

Extension of the DSMC method to high pressure flows

A collision-limiter method, designated as equilibrium direct simulation Monte Carlo (eDSMC), is proposed to extend the DSMC technique to high pressure flows. The method is similar to collision-limiter schemes considered in the past with the important distinction that for inviscid flows, equilibrium is enforced in the entire flow by providing a sufficient number of collisions, based on pre-simulation testing. To test the method with standard DSMC and Navier–Stokes (NS) methods, axi-symmetric nozzle and embedded-channel flows are simulated and compared with experimental temperature data and pre-existing calculations, respectively. The method is shown to agree with third-order Eulerian nozzle flows and first-order channel flows. Chapman–Enskog theory is utilized to predict the range of initial conditions where eDSMC is potentially useful for modeling flows that contain viscous boundary layer regions. Comparison with supersonic nozzle data suggests that the eDSMC method is not adequate for capturing the large variation in flow length scales occurring in supersonic expansions into a vacuum. However, when eDSMC is used in combination with the baseline-DSMC method a near-exact solution is obtained with a considerable computational savings compared to the exact DSMC solution. Viscous flow channel calculations are found to agree well with an exact Navier–Stokes (NS) calculation for a small Knudsen number case as predicted by Chapman–Enskog theory.     

Study of the heat-strength of PENTELAST one-component silicon adhesive-sealants

This work presents the results of testing the changes in the physical and mechanical parameters of PENTELAST adhesive-sealants due to isothermal aging at 200, 250, and 300°C within a period of 10 days. The operating temperature ranges are determined in which the PENTELAST adhesive-sealants may be used without impairing the strength and elastic properties. It is clearly shown that PENTELAST-1159 and PENTELAST-1161 materials have the maximal heat strength.     

The six-quark-admixture in the form factor of the3He at large transfer momenta

Elastic form factor of the³He nucleus is analysed with the use of Gaussian-type and realistic nuclear wave functions with a contribution of six-quark admixtures taken into account. The latter has been chosen so as to describe the data of analysis of cumulative and other processes and it amounts to about 8%. It is shown that unlike the deuteron form factor for³He the quark-nucleon interference is essential. The six-quark admixture does not remove the second minimum in the form factor of³He as a three-nucleon system atq ²~50 fm^?2. The comparison with other theoretical models and available experimental data is performed.     

The C13(d,α)B11 reaction

Russian Physics Journal -