Biomedical subjects

M V Sapozhnikov

Publications and source records attributed to M V Sapozhnikov.

6 recordsLinked to original sources

PubMed2005

Velocity distributions of granular gases with drag and with long-range interactions.

We study velocity statistics of electrostatically driven granular gases. For two different experiments, (i) nonmagnetic particles in a viscous fluid and (ii) magnetic particles in air, the velocity distribution is non-Maxwellian, and its high-energy tail is exponential, P(upsilon) approximately exp(-/upsilon/). This behavior is consistent with the kinetic theory of driven dissipative particles. For particles immersed in a fluid, viscous damping is responsible for the exponential tail, while for magnetic particles, long-range interactions cause the exponential tail. We conclude that velocity statistics of dissipative gases are sensitive to the fluid environment and to the form of the particle interaction.

Air Movements↗

PubMed2005

Far-from-equilibrium Ostwald ripening in electrostatically driven granular powders.

We report an experimental study of cluster size distributions in electrostatically driven granular submonolayers. The cluster size distribution in this far-from-equilibrium process exhibits dynamic scaling behavior characteristic of the (nearly equilibrium) Ostwald ripening, controlled by the attachment and detachment of the "gas" particles. The scaled size distribution, however, is different from the classical Wagner distribution obtained in the limit of a vanishingly small area fraction of the clusters. A much better agreement is found with the theory of Phys. Rev. E 65, 046117 (2002)] which accounts for the cluster merger.

Journal Article↗

PubMed2004

Self-assembly and vortices formed by microparticles in weak electrolytes.

We carried out experimental studies of the self-assembly of metallic micron-size particles in poorly conducting liquid subject to a constant electric field. Depending on the experimental conditions, the particles self-assemble into long chains directed along the electric field lines and form vortices and other structures. The vortices perform Brownian-type random motion due to self-induced chaotic hydrodynamic flows. We measured the diffusivity constant of the vortices and the conductivity and mechanical stiffness of the chains.

Journal Article↗

PubMed2004

Theory of pattern formation of metallic microparticles in poorly conducting liquids.

We develop a continuum theory of self-assembly and pattern formation in metallic microparticles immersed in a poorly conducting liquid in a dc electric field. The theory is formulated in terms of conservation laws for the densities of immobile particles (precipitate) and bouncing particles (gas) coupled to the Navier-Stokes equation for the liquid. This theory successfully reproduced the correct topology of the phase diagram and primary patterns observed in the experiment [Phys. Rev. Lett. 90, 114301 (2003)]]: static crystals, honeycombs, dynamic pulsating rings, and rotating multipetal vortices.

Journal Article↗

PubMed2003

Dynamic self-assembly and patterns in electrostatically driven granular media.

We show that granular media, consisting of metallic microparticles immersed in a poorly conducting liquid in a strong dc electric field, self-assemble into a rich variety of novel phases. These phases include static precipitates: honeycombs and Wigner crystals; and novel dynamic condensates: toroidal vortices and pulsating rings. The observed structures are explained by the interplay between charged granular gas and electrohydrodynamic convective flows in the liquid.

Journal Article↗

PubMed2003

Coarsening of granular clusters: Two types of scaling behaviors.

We report on an experimental study of small cluster dynamics during the coarsening process in driven granular submonolayers of 120-microm bronze particles. The techniques of electrostatic and vertical mechanical vibration were employed to excite the granular gas. We measure the scaling exponent for the evaporation of small clusters during coarsening. It was found that the surface area of small clusters S vs time t behaves as S to (t(0)-t)(2/3) for lower frequencies and S to (t(0)-t) for higher frequencies. We argue that the change in the scaling exponent is related to the transition from three-dimensional (3D) to 2D character of motion in the granular gas.

Journal Article↗