E. G. Bord

Hydrodynamic stability of the Poiseuille flow of dispersed fluid

The linear stability of a dispersed medium plane parallel flow is being investigated. The medium consists of carrier fluid and hard particles. Corresponding stability equations are obtained and then solved numerically. It is shown, that the flow stability essentially depends on particles sizes when the particle distribution is uniform. At the nonuniform dispersed-phase distribution the considerable factor determining the flow stability is the particles density distribution near the critical layer.

Instability of plane Couette flow of two-phase liquids

The stability of plane Couette flow of a disperse liquid (gaseous or liquid suspension) is investigated. It is shown that in contrast to the flow of a pure liquid (gas), above a certain threshold particle mass density, this flow begins to become unstable to infinitesimal perturbations.

Experimental and theoretical investigation of boundary layer perturbations on a low-aspect-ratio wing

Laminar-turbulent transition in a boundary layer of low-aspect-ratio wing was investigated. Experiments clarifying the flow structure, its mean and oscillatory characteristics were carried out accompanied by linear stability analysis of the wind tunnel data on the laminar flow velocity profiles. Theoretical results obtained in a parallel flow approximation are in a good agreement with the experimental data on disturbances evolution at the initial stage of transition to turbulence.

Development of laminar-separating-flow perturbations on a wavy wing

The development of velocity perturbations at laminar boundary-layer separation from a wing with wavy surface has been examined. Experiments were carried out to identify flow features displayed by the spatially periodic flow structure. An analysis of the linear stability of measured velocity profiles is performed. As a result of the analysis, the influence of surface waviness on the frequency range and growth rates of instability waves was investigated, with a good agreement between calculated and experimental data.

On Stability of Plane and Cylindrical Poiseuille Flows of Nanofluids

Stability of plane and cylindrical Poiseuille flows of nanofluids to comparatively small perturbations is studied. Ethylene glycol-based nanofluids with silicon dioxide particles are considered. The volume fraction of nanoparticles is varied from 0 to 10%, and the particle size is varied from 10 to 210 nm. Neutral stability curves are constructed, and the most unstable modes of disturbances are found. It is demonstrated that nanofluids are less stable than base fluids; the presence of particles leads to additional destabilization of the flow. The greater the volume fraction of nanoparticles and the smaller the particle size, the greater the degree of this additional destabilization. In this case, the critical Reynolds number significantly decreases, and the spectrum of unstable disturbances becomes different; in particular, even for the volume fraction of particles equal to 5%, the wave length of the most unstable disturbances of the nanofluid with particles approximately 20 nm in size decreases almost by a factor of 4.

Stochastic Properties of a System of Point Vortices

The dynamic and stochastic properties of a system of point vortices occurring at the vertices of a regular N-gon have been investigated. The time of reversibility of the phase trajectories was determined and their stability was studied. It is established that such a system exhibits stochastic properties only in the presence of a local instability, which is possible for N≥8.

Linear Stability of Two-Phase Flows

The laminar-turbulent transition problem remains one of the most actual problems of the mechanics and physics during the whole century. An essential progress in understanding this phenomenon was achieved when studying the steady laminar flow stability with respect to small external disturbances. However practically all achievements of the stability theory both theoretical arid experimental are relevant to the one phase fluid study.