[Show abstract][Hide abstract] ABSTRACT: An efficient numerical method for calculation of the turbulent mixing of hot air and flue gases in a vertical channel of arbitrary shape is developed in the paper. This method is used to study flows in high-rise constructions that combine a smokestack and a cooling tower. Flowfields, temperature and concentration distributions are calculated for various inlet conditions.
Full-text · Article · Dec 2015 · Procedia Engineering
[Show abstract][Hide abstract] ABSTRACT: The linear stability of a falling film of a surface-active solute is analyzed in an active evaporation zone. The phase velocities and the gain coefficients are calculated for the hydrodynamic and diffusion modes of perturbations.
No preview · Article · Mar 2013 · Moscow University Mechanics Bulletin
[Show abstract][Hide abstract] ABSTRACT: The decay of a Kármán vortex street and the formation of a secondary vortex structure in the far wake of a streamlined cylinder are studied. The dynamics of spatially evolving vortex structures is examined in the free flow and in the following ways of external influence on this flow: rotation with a constant velocity and translational and rotational oscillations of the cylinder. The results are obtained by numerically solving the Navier-Stokes equations with two different methods. The corresponding boundary value problems are formulated in the domains extended up to 500 radii of the cylinder.
Full-text · Article · May 2012 · Moscow University Mechanics Bulletin
[Show abstract][Hide abstract] ABSTRACT: A uniform viscous flow around a circular cylinder is studied numerically in the Reynolds number range from 0 to 500. It is
shown that the existence and the basic properties of self-oscillating regimes are specified by the evolution of their hydrodynamic
instability. It is found that the vortex formation in a near wake is associated with the separation zone dynamics in the main
flow. The values of critical Reynolds numbers for the four successive bifurcations of the self-oscillating regimes of flow
are obtained. An interpretation of experimental data on the vortices in the near wake is discussed.
Full-text · Article · Oct 2010 · Moscow University Mechanics Bulletin
[Show abstract][Hide abstract] ABSTRACT: The problem of the mixing of hot turbulent gases in an axisymmetric channel with a lateral surface of arbitrary shape and a pre-swirled flow is considered. The flowfields and the temperature and concentration distributions are calculated for various inlet conditions.
[Show abstract][Hide abstract] ABSTRACT: The instability of a falling liquid film of an aqueous surfactant solution along a vertical slope with surfactant adsorption-desorption at its open surface originating surface stresses (Marangoni effect) is investigated. The diffusion of surfactant to the film surface from the bulk and desorption of surfactant to the gas phase are taken into account. The Navier-Stokes and Fick equations are reduced to a system of simpler hence, analytically and numerically, more tractable nonlinear evolution equations albeit with nine dimensionless parameters. The linear stability analysis yields a dispersion equation that is numerically solved and eigenvalues are obtained for various values of significant dimensionless parameters. A very rich picture of instabilities appears. In addition to the earlier known (Kapitza) hydrodynamic mode there are up to four new (Marangoni-driven) diffusion modes. Two modes travel with the liquid velocity on the film surface and the other two travel on their own downstream and upstream, respectively. One diffusion mode could be identified, in the reference frame moving with the liquid on the film surface, as a monotonic instability mode hence leading to a patterned film surface. All other modes are oscillatory ones. Resonance of modes is also predicted for suitable combinations of the parameters of the problem. The mode observed depends upon the surface stress (in terms of a dimensionless Marangoni number), the particular choice of the adsorption-desorption kinetics, and the surface tension state equation at the open surface of the film.
Full-text · Article · Jun 2004 · Physical Review E
[Show abstract][Hide abstract] ABSTRACT: The hydrodynamic instability of a falling film of a dilute solution of a volatile surfactant is studied.
The flow of the “liquid-gas (vapor)” two-phase three-component system is accompanied by surfactant mass transfer across the free surface and is described by a system of five evolutionary equations for five functions depending on time and a spatial coordinate. These functions are the thicknesses of the film and the diffusion boundary layer, the concentrations of the free surfactant and the bound surfactant in the adsorbed sublayer, and the fluid velocity on the film surface. The dispersion equation determining the eigenvalues and the corresponding instability modes is solved numerically in the space of ten free nondimensional governing parameters. Main attention is focused on examining the role of the parameters controlling the influence of the surfactant on the Marangoni effect and the film instability at finite adsorption-desorption rates.
[Show abstract][Hide abstract] ABSTRACT: The hydrodynamic instability of a film flow of a weak solution containing a soluble volatile surfactant is investigated. Diffusion
of the surfactant in the liquid, its evaporation into the boundary gas medium, and the adsorption and desorption processes
in the near-surface layer are taken into account. A system of evolutionary equations is derived and a steady-state solution
film flow along a vertical surface and the stability of this flow are investigated for the simultaneous action of body and
capillary forces and the Marangoni effect. Hydrodynamic and diffusion instability modes are detected and their properties
are investigated for constant and variable surfactant concentration in the adsorbed sublayer.
[Show abstract][Hide abstract] ABSTRACT: The film flow of a weak solution of a soluble volatile surfactant in liquid is considered. Diffusion of the surfactant to the film surface from the bulk solute, its evaporation to the gas phase and the adsorption-desorption processes in the near-surface layer are taken into account. The full Navier-Stokes formulation is reduced to the system of nonlinear evolutionary equations. A model for the dynamic surface tension is appropriate for the transition of the freshly formed surface to the "old" surface to be investigated. A steady state solution for film flow along a slopped wall and instability of the flow are considered for the simultaneous action of the body forces, capillary pressure and Marangoni stresses. The nonlinear effects for the hydrodynamic and diffusion instability modes for non–equilibrium adsorption kinetics in the sorbed sublayer are investigated.
[Show abstract][Hide abstract] ABSTRACT: The method has been developed to calculate the thickness of liquid film on the solid surface being withdrawn from the liquid parcel. Examples are given for calculating the high-speed application of film coatings onto flat and cylindrical surfaces.
No preview · Article · · Moscow University Mechanics Bulletin