Dynamics of cryogenic jets: non-rayleigh breakup and onset of nonaxisymmetric motions

We report development of generators for periodic, satellite-free fluxes of monodisperse drops with diameters down to 10 microm from cryogenic liquids such as H2, N2, Ar, and Xe (and, as a reference fluid, water). While the break up of water jets can be described well by Rayleigh's linear theory, we find jet regimes for H2 and N2 which reveal deviations from this behavior. Thus, Rayleigh's theory is inappropriate for thin jets that exchange energy and/or mass with the surrounding medium. Moreover, at high evaporation rates, the axial symmetry of the dynamics is lost. When the drops pass into vacuum, frozen pellets form due to surface evaporation. The narrow width of the pellet flux paves the way towards various industrial and scientific applications.     

Electroacoustic waves confined by a moving domain wall superlattice of a ferroelectric crystal

The dispersion properties of electroacoustic wave modes confined by a superlattice of uniformly moving 180° domain walls in a tetragonal ferroelectric crystal are considered. It is shown that the manifold of partial electroacoustic interfacial waves in the lattice is restricted to the first allowed band, the configuration of which in the plane of spectral variables can significantly vary under the action of the moving domain walls.     

Seismoacoustic survey of artificial inhomogeneities in the ground

The results of processing the field test data obtained for the seismoacoustic system designed at the Institute of Applied Physics of the Russian Academy of Sciences for the visualization of underground engineering structures are presented. The described experiment is the first demonstration of the use of a high-power, high-stability transmitting-receiving system for producing a coherent insonification with a frequency of 195 Hz. The receiving element of the system is a synthetic aperture array. With the use of focusing as a method of the final signal processing, an image of a tunnel lying at a depth of 30 m is obtained in three spatial cross-sections, which demonstrates the possibility of a three-dimensional, coherent, high-frequency seismic survey of engineering structures.     

Hydrodynamic Dispersion for Fluid Filtration Through a Porous Medium with Random Macroscopic Inhomogeneities

Radiophysics and Quantum Electronics - We study the convective diffusion of passive admixtures in the course of forced fluid filtration through a porous medium with frozen random inhomogeneities of...     

An Effect of Sorption on Convective Modes Selection for Solutal Convection in a Rectangular Porous Channel

Transport in Porous Media - This paper is devoted to the stability analysis of 3D convective flow in the horizontal channel filled by the porous medium. Solute precipitation (solute sorption) by...     

Discretization of an admixture flux within the framework of the fractal model of anomalous diffusion

Within the framework of the fractal mobile-immobile medium model describing non-Fickian effects occurring in admixture seepage due to particle adhesion to the solid matrix, an expression for the admixture flux is derived. Flow discretization intended for finite-difference calculations is proposed and used as a basis for a conservation-law scheme for solving the model equations with account for admixture sources. Several one-dimensional test problems of admixture propagation in an imposed seepage flow are solved using the approach developed.     

Identifying Space-Dependent Coefficients and the Order of Fractionality in Fractional Advection–Diffusion Equation

Tracer tests in natural porous media sometimes show abnormalities that suggest considering a fractional variant of the advection–diffusion equation supplemented by a time derivative of non-integer order. We are describing an inverse method for this equation: It finds the order of the fractional derivative and the coefficients that achieve minimum discrepancy between solution and tracer data. Using an adjoint equation divides the computational effort by an amount proportional to the number of freedom degrees, which becomes large when some coefficients depend on space. Method accuracy is checked on synthetical data, and applicability to actual tracer test is demonstrated.     

Observation of slow dynamics effects in nonconsolidated media under in situ conditions

Reactions of an unconsolidated medium to a strong impact action are considered. A character of medium relaxation was controlled based on changes in the phase velocity of a trial Rayleigh wave. The analysis of the R-wave dispersion and its dependence on the distance to the source allowed for estimating the dimensions of a space region where the impact action was revealed. Seismoacoustic measurements showed that the time dependence of the R-wave is logarithmic.     

Laplace-Transform Based Inversion Method for Fractional Dispersion

Partial differential equations with memory are challenging models for mass transport in porous media where fluid and tracer may be stored by the solid matrix, and then released. Moreover, integral transforms (generalizing time moments) of solutions to such models are linked to the corresponding transport parameters. Inverting that link provides a method to determine model parameters on the basis of solutions. It is checked using numerically generated profiles before passing to experimental data.