PREFACE TO SPECIAL ISSUE MULTIPHASE FLOWS AND HEAT/MASS TRANSFER

Abstract

This issue is devoted to the problems of Multiphase Flows and Heat/Mass Transfer. Three papers included in this issue concern the theoretical investigations on the behavior of n onu iform hydrodynamical systems under the action of time-dependent external fields. The effects of pulsating pr essure field, external mechanical vibrations, and alternat ing electric field are discussed. In the paper by A.A. Alabuzhev, the dynamics of a cylindrical g seous bubble surrounded by a coaxial layer of incompressible fluid of different density and bounded in t he axial direction by parallel rigid plates with different properties are studied. The system is subjected to the pulsa ting pressure field. Velocity of three-phase contact line motion is assumed to be proportional to the contact angle dev iations. It is shown that, in some parameter ranges, the frequency of volume oscillations can be close to zero. If thi s frequency is close to one of the frequencies of shape oscillations, then a double resonance response is observed that leads the unlimited growth of oscillation amplitude independently of the coefficient of eigen-oscillation damp ing. E.S. Sadilov discusses the effect of normal vibrations on th e stability of a three-layer system of fluids in zero gravity conditions. It is found that, when the ratio of exter nal layer thicknesses tends to unity the critical vibration amplitude for subharmonic instability mode tends to infinit y, which means the disappearance of subharmonic instability mode for the external layers of equal thicknesses. Synch ronous instability mode exists at any ratio of the external layer thicknesses. The work “Electroconvection Instability of Poorly Conduct ing Fluid in Alternating Electric Field,” by N.N. Kartavykh and O.O. Nekrasov, deals with the study of a flat horizo ntal layer of a poorly conducting fluid subjected to the alternating electric field and heating from above. The el ectroconductive instability mechanism is analyzed. On the basis of the linear analysis, a map of the stability of a condu ctive state of nonuniformly poorly heated conducting fluid is plotted and the dependence of the critical wave numbers on the electric field frequency is obtained. Quasiperiodic, synchronous, and chaotic oscillation regimes are found as a re ult of the nonlinear system dynamics analysis. The domains of coexistence of oscillatory modes with different intensities of flows are found. In the work “Investigation of the Isothermal Rheokinetic Po lymerization of the Epoxy Oligomer,” by V.G. Gilev, V.S. Chudinov, S.V. Rusakov, and A.V. Kondyurin, an experim ental study and numerical simulations of the kinetics of polymerization of the epoxy oligomer were carried out. Nume rical analysis of the kinetic dependencies of viscosity allows one to estimate the reaction rate constants of the pol ymerization process, which makes it possible to predict the properties of the polymer during its formation. It is shown t hat the results of viscosity measurements can track quite well, not only the curing process of the binder but also its ra e. The article by K. Schweikert, A. Sielaff, and P. Stephan, “He at Flux during Dip-Coating of a Superheated Substrate,” is devoted to the transient heat flux calculations b ased on temperature measurements during the process of dipcoating of a superheated substrate. The surface temperatur e of the solid substrate is measured using high-resolution infrared thermography. Then, the obtained values were used a a boundary condition in simulations at the interface between the superheated substrate and the fluid. Two evapora tion regimes, namely, contact line evaporation and microlayer evaporation, were clearly distinguished by their magnitude in overall heat flux. The outflow of superheated fluid from the pipe channel into a cl osed volume is numerically simulated in the paper by M. Alekseev, I. Vozhakov, and S. Lezhnin. The simulations were carried out on the basis of a homogeneous onevelocity model. Distributions of pressure, velocity, and s team content in the volume are obtained. It was revealed that the distance between the pipe channel and the opposite wall a ffects the time to reach quasistationary values for the pressure and steam content. In the work by T. Gambaryan-Roisman, “Simultaneous Imbibit ion and Evaporation of Liquids on Grooved Substrates,” the hydrodynamics and heat and mass transport pro cesses on textured surfaces are described theoretically an d