Gas-liquid Medium Research Articles

Shock waves in water with Freon-12 bubbles and formation of gas hydrates

The evolution of a shock wave and its reflection from a wall in a gas-liquid medium with dissolution and hydration are experimentally investigated. Dissolution and hydration behind the front of a moderate-amplitude shock wave are demonstrated to be caused by fragmentation of gas bubbles, resulting in a drastic increase in the area of the interphase surface and in a decrease in size of gas inclusions. The mechanisms of hydration behind the wave front are examined. Hydration behind the front of a shock wave with a stepwise profile is theoretically analyzed.

Shock waves and formation of carbon dioxide hydrate at an increased pressure in the gas-liquid medium

The processes of breaking, solution, and formation of hydrates behind a shock wave of moderate amplitude were studied experimentally in water with carbon dioxide bubbles under different initial static pressures. It is shown that an increase in the static pressure in a gas-liquid medium leads to reduction of critical relative amplitude of the shock wave, corresponding to starting development of Kelvin — Helmholtz instability and bubble splitting into small gas inclusions behind the shock wave front. It is shown that the rates of carbon dioxide solution and hydrate formation behind the shock wave front are close by the value; their dependences on medium and wave parameters are determined. Calculations by the model of gas hydration behind the shock wave are presented.

The effect of static pressure on the formation of carbon dioxide hydrate behind the shock wave in the gas-liquid medium

The processes of crushing, dissolving and hydrate formation behind a shock wave of moderate amplitude in water with bubbles of carbon dioxide at various initial static pressures. Calculations are presented for the model of gas hydration behind a shock wave.

Pressure waves in a tube filled with a bubbly mixture with a nonuniform cross-sectional bubble distribution

The evolution of pressure waves in a tube filled with a gas-liquid medium with a stepped cross-sectional bubble distribution is investigated. The calculations are compared with experimental data. It is shown that in the case of a nonuniform bubble distribution, due to the appearance of transverse flows, the pressure pulse is damped faster than for a uniform distribution. The interaction of pressure waves with a bubble cluster in a tube filled with liquid is also analyzed.

Numerical Analysis of Cavitation Instabilities and the Suppression in Cascade

In this study, unsteady cavitation and cavitation instabilities are numericaly analyzed around cascades in water/air working fluid. The numerical method employing a locally homogeneous model of compressible gas-liquid two-phase medium is applied, because it permits the entire flowfield inside and outside the cavity to be simulated easily through only one system of governing equations. Three types of.cavitation instabilities, which are similar to “cavitation surge”, “forward rotating cavitation” and “rotating-stall cavitation”, are represented numerically in flat-plate cascade under three-blade cyclic condition. Additionally, flowfields around flat-plate cascade with slit on blade are analyzed in the conditions where the three types of cavitation instabilities arise in the cascade without slit. The effect of the slit on suppression of cavitation instabilities is confirmed from the present numerical results.

Propagation of pressure waves in a gas-liquid medium with a cluster structure

Propagation of a stepwise shock wave in a liquid containing spherical gas-liquid clusters is experimentally studied. Measured results are compared with available theoretical models. It is shown that resonant interaction of gas-liquid clusters in the wave can increase the amplitude of oscillations in the shock wave.

Features of the Motion of a Gas-Liquid Medium in a Compound Shell (Sphere and Truncated Cone) Subject to Vibration

The results from an experimental study into the dynamic behavior of a gas-liquid medium and solid particles in a compound shell (sphere-truncated cone) are reported on. The following processes are studied: formation of gas bubbles and their clusters, strong macroflows, and intensive chaotic motion of the medium in the truncated cone as a nonlinear vibrating liquid-gas system

Numerical Analysis of Cavitation Instabilities Arising in the Three-Blade Cascade

Three types of cavitation instabilities through flat plate cascades, which are similar to “forward rotating cavitation,” “rotating-stall cavitation” and “cavitation surge” occurring in high-speed rotating fluid machinery, are represented numerically under the three-blade cyclic condition. A numerical method employing a locally homogeneous model of compressible gas-liquid two-phase medium is applied to solve the above flow fields, because this permits the entire flow field inside and outside the cavity to be treated through only one system of governing equations. In addition, the numerical method suites to analyze unsteady cavitating flow with a long time evolution. From the calculated results of the present numerical simulation with wide range of cavitation number and flow rate, we obtain a cavitation performance curve of the present three-blade cyclic cascade, analyze the aspects of unsteady cavitation, and discuss the characteristics and mechanisms of cavitation.

Evolution of a shock wave in a clustered gas-liquid medium

Evolution of a shock wave in a clustered gas-liquid medium

Immersion Tomography of a Gas–Liquid Medium in a Granular Bed

Observed data are presented to demonstrate the wide experimental possibilities opened by a method for visualizing a gas–liquid medium in fixed and fluidized granular beds by immersion tomography. The immersion tomography method stems from the fact that, by selecting the properties of an immersion liquid in a particular way, it is possible to keep the medium optically transparent (by varying dimensionless hydrodynamic and heat- and mass-transfer parameters) and also to reconstruct a three-dimensional image of the granular bed. The method was used to study the free rise of single gas bubbles in a fixed granular bed formed by glass beads 7 mm in diameter.

Numerical Study of Sheet Cavitation Breakoff Phenomenon on a Cascade Hydrofoil

Two-dimensional unsteady cavity flow through a cascade of hydrofoils is numerically calculated. Particular attention is focused on instability phenomena of a sheet cavity in the transient cavitation condition, and the mechanism of the breakoff phenomenon is examined. TVD-MacCormack’s scheme employing a locally homogeneous model of compressible gas-liquid two-phase medium is applied to analyze the cavity flows. The present method permits us to treat the entire cavitating/noncavitating unsteady flowfield. By analyzing the numerical results in detail, it becomes clear that there are at least two mechanisms in the breakoff phenomenon of the sheet cavity: one is that re-entrant jets play a dominant role in such a breakoff phenomenon, and the other is that pressure waves propagating inside the cavity bring about another type of breakoff phenomenon accompanying with cavity surface waves.

Pressure waves in a gas-liquid medium with a stratified liquid-bubbly mixture structure

Evolution and decay of pressure waves of moderate amplitude in a vertical shock tube filled by a gas–liquid medium with a nonuniform (stepwise) distribution of bubbles over the tube cross section are studied experimentally. The gas–liquid layer has the form of a ring located near the tube wall or the form of a gas–liquid column located in the center of the tube. It is shown that the nonuniformity of bubble distribution over the tube cross section increases the attenuation rate of pressure waves.

Roll waves in a gas–liquid medium

The one‐velocity motion of a gas–liquid medium with a variable mass fraction of the gas phase, which is equilibrium in terms of phase pressures, is considered. The existence conditions of nonlinear periodic wave packets similar in structure to roll waves in open inclined channels are found. The structure of travelling waves in the medium with continuous addition of energy to the gas phase is studied.

Dynamics of a Gas–Liquid Medium in a Torus-Like Shell Under Vibratory Actions

The results of experimental studies into the resonance vibration of a free liquid surface and gas–liquid medium in a torus-like shell are presented

Vibration effects of the dynamic interaction between a gas-liquid medium and elastic shells

The paper presents the results of experimental investigations of regimes of the nonlinear deformation of elastic shells filled with a liquid. These regimes are due to the interaction of local clusters of gas bubbles formed in a vibrating liquid with the vibration modes of an elastic shell excited in the circumferential and longitudinal directions.

Possibility of reaching higher contents of a gas in a liquid using shock waves

The effect of shock waves on gas absorption by liquid in bubbly media with different degrees of gas solubility is studied. It is shown that a shock wave acting on a gas-liquid medium can significantly enhance the mass transfer between the gas and the liquid.

Cell model for gas absorption with first-order irreversible chemical reaction and heat release in gas-liquid bubbly media

A model for mass and heat transfer during physical gas absorption in gas-liquid bubbly medium suggested in [1] is generalized for a case of chemical absorption accompanied by heat release. Diffusion and thermal interactions between bubbles are taken in to account in the approximation of a cellular model of a bubbly medium whereby a bubbly medium is viewed as a periodic structure consisting of identical spherical cells with periodic boundary conditions at a cell boundary. Distribution of concentration of the dissolved gas, temperature distribution in liquid and rates of mass and heat transfer during nonisothermal chemical absorption of a soluble pure gas from a bubble by liquid are determined. In the limiting case of chemical absorption without heat release the derived formulas recover the expressions for isothermal chemical absorption. In the limiting case of physical absorption with heat release the derived formulas recover the expressions for nonisothermal absorption obtained in [1].

Nonlinear physical characteristics of a high-voltage electric discharge in a two-phase liquid

Physical features of an electric discharge in a gas-liquid medium are investigated; a direct relationship between the entropy change and the fractal nature of the medium itself is shown. Simplified equations and laws of conservation that describe the dynamics of the electric discharge in the two-phase liquid with allowance for the thermodynamic properties of the medium as functions of its fractal structure are used.

Dynamic behavior of liquids and gases in conical shells in a vibrational force field

An experimental study is made of specific features of the motion of the free surface of liquid in different conical shells, the formation, motion, and local accumulation of gas bubbles in the shells, and the character of random motion of the gas-liquid medium in a vibrational force field. It is established that the liquid moves along the horizontal as well as the vertical axes under certain conditions when axisymmetric modes of vibration of the free surface are excited. The main characteristics of the dynamic behavior of a gas-liquid medium in a compound conical shell having the form of a de Laval nozzle are examined for the case when the medium forms a nonlinear oscillatory “liquid-gas” system that is dynamically stable.

Propagation of Nonlinear Waves in a Spatially Nonuniform Gas-Liquid Medium

Specific features of the evolution of nonlinear pulse disturbances in a bubbly gas-liquid medium with periodic variation of the gas void fraction in the pulse propagation direction are studied. The effect of the period and amplitude of the void fraction nonuniformity on the propagation of a single pulse is analyzed both with and without account for heat transfer in the medium. It is demonstrated that taking the heat transfer into account has no impact on the qualitative flow pattern.