Break-up of a drop in a stirred tank

The drop break-up mechanism was studied in a stirred tank containing two immiscible liquids. The daughter drops formed by break-up of a single drop of known size were recorded photographically. From the experiments at constant agitator speed the following results were obtained. There is a critical drop size under which drops do not break up under given conditions. The break-up frequency increases approximately linearly with increase in drop volume. The number of daughter drops, v, is a random variable with a mean v > 2 which increases with the volume of the mother drop. The relative volume of a daughter drop has a β-distribution.     

Motion of a shaped-charge jet in a porous medium

The problem of the motion of a shaped-charge jet in a porous medium is equivalent to the problem of a blunt cylinder in a hypersonic flow whose velocity at infinity is equal to the jet velocity in the porous medium. The flow pattern of the medium is the same as in the case of propagation of a blast wave generated by a point explosion of a cylindrical charge. The approximate theory of a strong explosion is used to obtain the basic relations for the shock wave and the expanding cavity in the hypersonic flow of a porous medium around the blunt cylinder. A comparison with experiments on the motion of a copper shaped-charge jet in porous aluminum is performed. Translated fromFizika Goreniya i Vzryva, Vol. 35, No. 6, pp. 119–124, November–December 1999.     

Interaction of a Shock Wave with a Cloud of Aluminum Particles in a Channel

Interaction of an incident shock wave (with a rectangular or triangular profile behind its front) with a finite-width semi-infinite cloud of aluminum particles located in a channel along the plane of symmetry is numerically simulated. Shock-wave interaction with the leading edge of the cloud results in the formation of a vortex that leads to cloud dispersion. Reflection of the curved shock wave from the plane of symmetry may be regular or may include the formation of the Mach stem. If the cloud is loaded by a rather strong shock wave, a detonation wave is formed in the cloud. In this case, the flow is periodic, which is caused by passing of transverse waves and their reflection from the walls.     

Fractionation of a diblock copolymer in a demixing-solvent system

Phase behavior of a hydrogenated styrene/isoprene diblock copolymer in a dimethylformamide/methylcyclohexane demixing-solvent pair has been studied. At a fixed copolymer concentration (1% w/v), the scheme of phase behavior (temperature vs. mixed-solvent composition) of the system has been found to be complex, with several areas where various supramolecular structures are spontaneously formed. In a particular area of the scheme, a multistep demixing-solvent fractionation of the copolymer has been performed. The resulting fractions have been characterized and the data used to construct integral distribution functions of copolymer molar mass and copolymer composition. These functions have been compared with those obtained by a previously reported light-scattering characterization of the whole, unfractionated, nonhydrogenated precursor of the copolymer © 1993 John Wiley & Sons, Inc.     

Detonation of a Column of a Chemically Active Bubbly Medium in a Liquid

The problem of a detonation wave propagating in a cylindrical column of a chemically active bubbly medium screened by a liquid from the tube walls is formulated and numerically solved within the framework of the Iordanskii–Kogarko two-phase model with allowance for energy dissipation due to acoustic radiation of bubbles. The wave structure of the reaction zone and the detonation velocity of the bubbly medium column are calculated. It is found that the self-sustaining wave can propagate with a velocity greater than the velocity of one-dimensional bubble detonation by a factor of 1.5–2.5.     

Thermal Processing of Dripping Substances in a Capsular Envelope Submerged in a Boiling Liquid in a Vacuum

The principal scheme of cooling liquid-drop substances in a capsulated envelope submerged in an intermediate water environment, which is boiling in a vacuum is presented. The correlations that allow estimating the cooling time of the product to the given temperature and accounting for the temperature of the intermediate liquid are obtained. The experimental stand and methodology for obtaining the empirical data are described. A comparison of the theoretical and experimental research shows satisfactory convergence and therefore the computation results can be used to design cooling facilities.     

Transient Outflow of a Liquid from a System of Holes in a Horizontal Tube

The transient outflow of a liquid from a perforated horizontal tube as a result of abruptly applied constant pressure is studied theoretically and experimentally. Equations and a computer program are developed for estimating the parameters of such transient processes. Retardation of the liquid outflow is observed, and its mechanism is discussed.     

Laminar flow deformation of a droplet adhering to a wall in a channel

We study the deformation of oil droplets of varying viscosity adhering to a solid, rigid wall in a rectangular channel induced by a pressure-driven, laminar flow of water. Our experimental investigation involves the systematic study of the effects of initial droplet volume, flow rate and viscosity ratio on the various modes of droplet motion and deformation; this is performed via direct visualisation of the flow in a glass cell using a high-speed camera. Our results are used to construct flow maps that delineate the critical conditions for droplet ‘sliding’, ‘crawling’ and detachment from the channel wall as a function of system parameters. Comparisons of our experimental results with numerical predictions obtained using a procedure based on the diffuse-interface method yield reasonably good agreement for certain flow regimes.     

Mesomorphic transitions in a mixture of a flexible and a semi-rigid polymer

Phase studies on a mixture of two polymers are presented, one of which is mesomorphic. We have systematically examined the influence of the molecular weight of the flexible polymer (including the oligomers) and of the semi-flexible polymer. In addition to the effect of the molecular weight, specific interactions are important for compatibility and formation of a homogeneous mesomorphic phase. The nature of this phase is demonstrated to be cholesteric and the pitch is determined.     

Reflection of a shock wave in a dusty cloud

The problem of shock-wave passage along a cloud of particles adjacent to a solid surface is studied numerically and analytically. The wave pattern of the flow near the shock wave reflected from this surface is analyzed within the framework of the equilibrium approximation of mechanics of heterogeneous media. The conditions of the transition from regular to irregular reflection from the substrate of the refracted shock wave inside the cloud are obtained analytically. The results of numerical simulations of a nonequilibrium flow in the two-velocity two-temperature approximation are compared with data obtained in the equilibrium approximation. Nonequilibrium and equilibrium flows are found to become more similar as the particle size decreases. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 1, pp. 121–131, January–February, 2007.     

Limits of detonation propagation in a suspension of propellant particles in vacuum in a tube

The problem of stationary detonation in vacuum with monopropellant particles propagating in a tube is formulated and analyzed numerically. It is shown that friction and heat removal onto the tube walls affect the structure of a disperse wave. The dependences of the detonation velocity on the tube diameter, the size of the propellant particles, and on their mass concentration have been determined, and the limits of detonation propagation have been found.Lavrent'ev Institute of Hydrodynamics, Russian Academy of Sciences, 630090 Novosibirsk. Translated from Fizika Goreniya i Vzryva, Vol. 30, No. 2, pp. 76–84, March–April, 1994.     

Mixing of a lateral gas stream in a two-dimensional riser of a circulating fluidized bed

A cold model of a circulating fluidized bed having a two-dimensional riser, with a 12 × 120 mm section and a 6.4 m height, was equipped with a device to inject a lateral gas stream along the riser. The apparatus was operated under conditions ranging from those characteristic of combustors to those of gas-conversion processes. Flow structures in the interaction region between the rising gas—solids suspension and the lateral gas stream were studied by means of a motion analysis system. Three main configurations were identified. The ratio between the momentum of the lateral gas stream and that of the rising suspension was found to be the parameter able to discriminate among the three configurations. A satisfactory agreement was found with mixing data obtained using a cylindrical riser.     

Continuous detonation in a supersonic flow of a hydrogen-oxygen mixture

The problem of continuous spin detonation in a supersonic flow in a flow-type annular combustor is considered in a two-dimensional unsteady formulation. The dynamics of the detonation wave in a hydrogen-oxygen mixture with isentropic and shock-wave compression of the flow in the input diffuser is studied. It is shown that the mass flow rate of the mixture through the combustor decreases as continuous spin detonation is formed, and a steady regime with a “detached” shock wave is observed at the entrance of the supersonic diffuser. For a contoured combustor, the limit from above is obtained for the Mach number of the incoming supersonic flow at which a continuous detonation regime is obtained.     

Life of refractories in service in a furnace for melting in a molten bath

Conclusions As the result of laboratory and production tests it was established that the periclase-chromite refractories produced from fused material show the greatest life in the lining of furnaces for melting in a molten bath.A method of production of fused chromite-periclase used for the production of fused periclase-chromite refactories to Technical Specification (TU) 14-8-368-81 was developed.A design of combined lining of a furnace for melting in a molten bath with the use of highly resistant refractories was developed.Translated from Ogneupory, No. 1, pp. 56–60, January, 1986.     

The thermal history of a granule in a rotary cooler

A formula is developed (from which a computer program has been written) that allows the temperature to be calculated of a granule that undergoes alernating periods of being cooled and of being allowed to ‘soak’ without cooling. This is the process, repeated many times, that a particle suffers in a rotary cooler. The result should provide a design method that utilizes only basic physical quantities.     

Drag of a cylinder moving near a wall in a yield stress fluid

The drag of a cylindrical obstacle moving at a constant velocity in a yield stress fluid close to a wall is studied experimentally and numerically. The wall influence has been explored for gap values between the cylinder of diameter D and the wall ranging from 0.01D to 100D, which corresponds, respectively, to hydrodynamic lubrication and to unconfined domain conditions. A model yield stress fluid (Carbopol gel) is used in the experiments. The viscous and plastic drag coefficients have been calculated and measured as depending on the Oldroyd number, in conditions where the yield stress effects are more important than those of viscosity and the inertia negligible. We have performed experimental and numerical validations in the Newtonian case and provided more specifically comparisons of our measured data on yield stress materials with those resulting from viscoplastic flow simulations. © 2018 American Institute of Chemical Engineers AIChE J, 64: 4118–4130, 2018     

Production of periclase in a furnace with a current-conducting bottom

Conclusions In smelting magnesite in a furnace with a current-conducting bottom, the operation of igniting the furnace is eliminated and this increases by 3.4% the productivity of a furnace operating on fired magnesite.An increase in the depth of the periclase-melting zone leads to a 0.55% increase in the consumption of electric power, a 0.5% reduction in the total concentration in the periclase of oxides of iron, silicon, and aluminum and in the loss on ignition, and a 20–30% improvement in the values of the dielectric properties of periclase.Translated from Ogneupory, No. 2, pp. 33–35, February, 1984.     

Coexistence in a chemostat: Application of a threshold policy

A well known result in chemostat theory states that two populations of microorganisms which compete for a single limiting nutrient cannot coexist under the condition of a spatially uniform environment and time invariant external influences. In this same setting, altering the dilution rate by means of a threshold policy can revert competitive exclusion to species coexistence in a vicinity of a previously chosen concentration.     

Combustion of a liquid fuel in a rectangular channel

The possibility of flame spread over the surface of a liquid fuel (n-butanol) in two-phase flow with a gaseous oxidizer in a narrow rectangular channel is demonstrated. The results of a detailed experimental study of combustion in this system are given. Dependences of the flame propagation speed on the initial temperature and oxidizer and fuel flow rates are obtained.     

The stability of a steam-water front in a porous medium

We present a first order stability analysis of a steam-water front moving through a porous medium. The interplay between gravity, mobility and phase change are investigated. Several new phasical effects are observed in this dynamic study (e.g. oscillatory solutions, multiple solutions, etc.) and a number of specific limiting solutions are also considered.