Vibrational convection in a saturated porous medium in the absence of thermal equilibrium between the solid and liquid phases

Thermal vibrational convection in a saturated porous medium is theoretically studied on the basis of a thermal nonequilibrium model, in accordance with which the temperatures of the porous medium and the saturating liquid can be different. In the high-frequency vibration approximation the averaged equations of convection are derived. The dependence of the vibration force direction on the interphase heat transfer coefficient and the vibration frequency is established. Vibrational convection in a cylindrical layer is studied. It is shown that, depending on the interphase heat transfer coefficient, the flows of two types differing in the liquid circulation direction can exist.     

Convective stability of fluid in a rotating horizontal annulus

The convective stability of quasi-equilibriumof a fluid layer formed by two horizontal coaxial cylindrical surfaces which have different temperatures and rotate at the same angular velocity about the axis of symmetry is investigated theoretically and experimentally. Consideration is carried out from the standpoint of thermal vibrational convection caused by the average lifting force generated as a result of vibrations of a nonisothermal fluid with respect to the cavity. The vibrations are induced by an external field. The action of the centrifugal force field is also taken into account. Stability of mechanical quasi-equilibrium with respect to monotonic plane perturbations, which are, as shown experimentally, the most dangerous, is studied within the framework of the linear analysis. The stability boundaries are constructed for layers of various relative thickness in the plane of control parameters, the centrifugal and vibrational Rayleigh numbers. The thresholds of excitation of two-dimensional convective structures obtained experimentally are in good agreement with the theoretical ones.     

Vibrational thermal convection about a uniformly heated cylinder

Vibrational convection under conditions of weightlessness has now been investigated for closed cavities of various geometries (see, for example, [1–3]). However, the question of vibrational convection developing around a heated body in an unconfined fluid remains open. Here, the convection developing under conditions of weightlessness about a uniformly heated infinite cylinder vibrating at high frequencies together with the fluid in a direction perpendicular to the cylinder axis is considered. The nonlinear equations of averaged motion are solved numerically by a finite-difference method. It is shown that at high values of the vibrational Grashof number boundary-layer type flow with a structure consisting of two symmetrical jets perpendicular to the direction of vibration is formed. The flow and heat transfer characteristics are determined.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 3, pp. 23–26, May–June, 1989.The author wishes to thank E. M. Zhukovitskii for supervising the work.     

Chemoconvective Structures in a Rotating System of Reacting Liquids

Journal of Applied Mechanics and Technical Physics - Chemoconvective structures in a system of two reacting miscible liquids, placed in a cylindrical Hele-Shaw cell rotated uniformly around the...     

Competition between BCS and FFLO States in Magnetic Superconductors in a Cryptoferromagnetic Phase

The possibility of appearance of inhomogeneous superconducting Fulde—Ferrell—Larkin—Ovchinnikov (FFLO) states in magnetic superconductors in a cryptoferromagnetic phase with helical magnetic ordering has been analyzed. The dependence of the critical temperature on the angle between the wave vectors of the spatial modulation of the FFLO state and helical magnetic structure has been calculated within the proposed model. It has been shown that their mutually perpendicular orientation corresponds to the most energetically favorable state. The numerical calculations have also shown the existence of a tricritical point on a line separating the Bardeen—Cooper—Schrieffer and FFLO phases on the phase diagram of states. Furthermore, FFLO states can appear in a magnetic superconductor even at fairly strong exchange fields because of the difference between the effective masses of conduction electrons in different spin subbands and the anisotropy of the Fermi surface.

     

Supramolecular Catalytic Systems Based on a Cationic Amphiphile and Sodium Polystyrene Sulfonate for Decomposition of Organophosphorus Pollutants

Russian Journal of Organic Chemistry - A supramolecular catalytic system for hydrolytic decomposition of toxic phosphorus acid esters has been obtained on the basis of a cationic surfactant with a...     

Investigation of convection in a horizontal cylindrical layer of a saturated porous medium

The structures of the convective motions and the nature of the heat transfer in a horizontal cylindrical layer are studied numerically for the Forchheimer model of a porous medium in the Boussinesq approximation. New asymmetric solutions of the equations of convection flow through a porous medium are found. Their development, domains of existence, and stability are investigated. One consists of a multivortex structure with asymmetric vortices in the near-polar region. Another asymmetric solution is realized at large Grashof numbers in the form of a convective plume deflected from the vertical. The threshold Grashof number of formation of the asymmetric motions depends on the Prandtl number and the cylindrical layer thickness.     

Axisymmetric convective boundary layer in a vibrating fluid

A vibrating convective flow around a uniformly heated sphere in weightlessness conditions is studied theoretically for circularly polarized vibrations. It is found that the fluid motion has the form of two jets spreading from the sphere in opposite directions along the symmetry axis, perpendicular to the vibration polarization plane. For large characteristic temperature gradients, the flow becomes self-similar. The equations describing thermovibrational convection in the boundary layer approximation are derived. A class of self-similar solutions for a point heat source is found. The results obtained on the basis of the full equations and in the boundary layer approximation are compared.