Numerical and experimental study of the fine structure of a stratified fluid flow over a circular cylinder

The fine structure of the flow field of a continuously stratified fluid around a circular cylinder for small values of the Froude number was investigated in laboratory and numerical experiments. The parameters of the leading perturbation, the internal-wave field, and the cylinder wake were calculated using a two-dimensional model. The existence of the previously experimentally observed high-gradient density layers in the wake that are parallel to the flow axis was for the first time confirmed by numerical calculations. Results of the numerical and experimental studies are in good agreement with each other and with analytical models for small values of the Froude number. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 1, pp. 43–54, January–February, 2007.     

Asymptotic structure of inviscid disturbances in a thin shock layer

The WKB method, used in [4] to analyze the short-wave instability of a supersonic mixing layer, is employed to investigate various types of inviscid three-dimensional short-wave disturbances in a thin shock layer of perfect gas with arbitrary velocity and temperature distributions across the layer. Simple analytic expressions for the dispersion relations are obtained for neutral disturbances. The results of an asymptotic analysis are compared with direct numerical calculations for a simple model of the shock layer.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 72–79, November–December, 1988.     

Short-wave instability in a perfect-gas shock layer

Asymptotic methods are used to investigate the regime of two interacting waveguides. As a result of an analysis of the dispersion relation short-wave instability of the acoustic type is detected. It is shown that this instability is convective. A qualitative comparison with direct numerical calculations is carried out using a simple model of the flow in the shock layer.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 10–14, January–February, 1989.     

Exact solution of an automodel (self-sustaining) problem regarding the motion of a nonviscous heat-conducting gas bounded by a vacuum

The one-dimensional transient motion of a nonviscous, compressible, heat-conducting, gas bordered on one side by free space and on the other by a solid wall is considered. The boundary conditions at the wall are taken in a form which ensures an automodel (self-sustaining) state. An exact solution is obtained for the problem, and this is then compared with a numerical calculation.     

Vortex formation mechanisms in the wake behind a sphere for 200 < Re < 380

Direct numerical simulation and visualization of three-dimensional separated flows of a homogeneous incompressible viscous fluid are used to comprehensively describe different mechanisms of vortex formation behind a sphere at moderate Reynolds numbers (200 ≤ Re ≤ 380). For 200 < Re ≤ 270 a steady-state rectilinear double-filament wake is formed, while for Re > 270 it is a chain of vortex loops. The three unsteady periodic flow patterns corresponding to the 270 < Re ≤ 290, 290 < Re ≤ 320, and 320 < Re ≤ 380 ranges are characterized by different vortex formation mechanisms. Direct numerical simulation is based on the Meranzh (SMIF) method of splitting in physical factors with an explicit hybrid finite-difference scheme which possesses the following properties: secondorder approximation in the spatial variables, minimal scheme viscosity and dispersion, and monotonicity. Two different vortex identification techniques are used for visualizing the vortex structures within the wake.     

Crystal structure and EPR spectra of (Bu<Subscript>4</Subscript>N)<Subscript>2</Subscript>[V(dmit)<Subscript>3</Subscript>]

The tris-chelate complex of vanadium(IV) (Bu₄N)₂[V(dmit)₃] is prepared from VCl₃ and (Bu₄N)₂[Zn(dmit)₂] (dmit = isotrithionedithiolate C₃S₅ ^2–) and characterized by single crystal XRD and mass spectrometry. The complex crystallizes in the space group Pna2₁ and has a distorted octahedral environment of vanadium. The complex is paramagnetic and gives a characteristic EPR spectrum in both solution and solid phase. The g factors and hyperfine interaction constants are determined.     

A study of the quality of a layered spherical dielectric resonator

The dependence of the quality of a screened layered spherical resonator on its geometric and electrodynamic parameters is studied in the case of a three-layer dielectric filling on the basis of a mathematical model constructed in the paper.