Non-linear dynamics and pattern formation in a vertical fluid layer heated from the side

We study both experimentally and numerically the convective flow in a tall vertical slot with differently heated walls. The flow is investigated for the fluid with the Prandtl number Pr=26, which is large enough to ensure the traveling waves as primary instability and small enough to prevent boundary layer convection. The flow evolution is determined on the base of the visual observations, power spectra and amplitude analysis. In the numerical simulations of two- and three-dimensional flows, we accept an assumption of an infinite fluid layer. The satisfactory agreement with experiment is observed, and the sequence of convection states is discovered. It starts with a plane-parallel flow as primary solution, which becomes unstable to two counter-propagating waves. It is followed by a tertiary three-dimensional flow in the form of wavy traveling waves. As the Grashof number is increased even further, a chaotically oscillating cellular pattern consisting of the pieces of broken waves arises. The formation of a structure in the form of the vertical rolls chaotically modulated along axes concludes this complicated picture.     

Measurement of inertial microaccelerations with the use of convection sensors

The influence of external seismic actions on the convective flows in a Hele-Shaw cell heated from below is investigated theoretically. The temperature and velocity fields and the patterns of flows are calculated in the cases of the detection of vertical and horizontal seismic signals. The results of the calculations will be used in the design of an instrument for detecting microaccelerations of seismic origin. The working fluid is chosen and the optimum geometric parameters of the cavity of the convection sensor are determined using numerical simulation.     

Physicochemical properties of composite sorption-active materials based on zeolite and fluorinated ethylene derivatives

A procedure was suggested for preparing composite sorption-active materials based on zeolite and fluorinated ethylene polymers. The morphology of these materials, their resistance to mechanical action, and their ability to sorb water vapor under static and dynamic conditions were examined.     

Separation of mixtures in connected channels

The stationary modes of thermal convection of a binary mixture in connected channels of finite height were studied experimentally and theoretically. The effects of positive and negative thermal diffusion on the convection were examined. The ranges of parameters corresponding to the modes of soft and rigid initiation of convection were determined. Vertical distributions of the temperature and concentration fields were found for various values of the thermal diffusion parameter. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 50, No. 1, pp. 68–77, January–February, 2009.     

Intrapore convection when the average temperature gradient is vertical

The heat conduction of a porous medium saturated with a fluid is usually regarded as being purely molecular [1]. The assumption here is that in the case of heating from below the local temperature gradient within each of the pores, like the averaged gradient in the complete layer, is strictly vertical, and, since the pores are as a rule small, this local gradient is less than the critical. It is therefore assumed that in the absence of large-scale convection the fluid in the pores is in equilibrium. However, for different thermal conductivities of the fluid and the porous skeleton surrounding it a vertical temperature gradient in the fluid and, accordingly, equilibrium of the fluid are possible only if a cavity is a sphere or an ellipsoid with a definite orientation [1]. Since the pores do not have such shapes, the convective motion that arises in each of the pores or in several communicating pores can lead to an increase in the effective thermal conductivity of the fluid and, accordingly, the effective thermal conductivity of the complete medium. The present paper is devoted to study of this effect.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 93–98, January–February, 1984.     

Experimental and theoretical investigation of thermal convection in a terrestrial model of a convection detector

The effect of small inclinations and low-amplitude rocking on thermal convection in an air-filled cube with sides 3 cm long has been investigated experimentally and numerically for steady and periodic heating from above. Expressions have been obtained for the dependence of the temperature difference between two points inside the cube on the angle of inclination, the applied vertical temperature difference, the rocking frequencies and the oscillations of the heating power. The possibility of estimating the magnitude and direction of the microacceleration vector on the basis of temperature field measurements made under orbital flight conditions is discussed.Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 5, pp. 67–75, September–October, 1994.     

Adsorption properties of the MOF-5 metal-organic framework in relation to water and benzene

Adsorption properties of synthesized metal-organic frameworks based on 1,4-dicarboxylate ligands and zinc ions were studied. It was shown that the adsorption properties of these metal-organic frameworks in relation to water and benzene are much higher than those for the known adsorbents: KT-1 and KT-2 coals, USY and ZSM-5 zeolites, and pentasil.     

Spatio-temporal chaos in colloid convection

The gravity convection in a plane horizontal colloid layer heated from below has been investigated experimentally and numerically. The temperatures and heat fluxes were measured using thermocouples. The flows were visualized using a thermosensitive liquid-crystal film. The Fourier and wavelet spectra of the thermal signals have been calculated. The numerical calculations were based on the model of a two-phase mixture of rigid particles with a carrier fluid. It was found that in colloids the branching-off of convective flows from mechanical equilibrium is hard and has an hysteresis. On the investigated interval up to four supercriticalities the spatio-temporal structures are irregular and wavy, which can be attributed to the competition between thermally and barometrically induced density drops.     

Comparison of the Activities of Pd(0) and Pd(I) in Low-Temperature Oxidation of Carbon Monoxide on the Pd/γ-Al2O3 Catalyst

Kinetics and Catalysis - Low-temperature oxidation of carbon monoxide on the Pd/γ-Al2O3 catalyst has been studied at room temperature and atmospheric pressure of air containing 100 mg/m3 CO....