arXiv subjects

Kengo Ichiki

Publications and source records attributed to Kengo Ichiki.

5 recordsLinked to original sources

arXiv2013

Resistance functions for two unequal spheres in linear flow at low Reynolds number with the Navier slip boundary condition

Resistance functions for two spherical particles with the Navier slip boundary condition in general linear flows, including rigid translation, rigid rotation, and strain, at low Reynolds number are derived by the method of reflections as well as twin multipole expansions. In the solutions, particle radii and slip lengths can be chosen independently. In the course of calculations, single-sphere problem with the slip boundary condition is solved by Lamb's general solution and the expression of multipole expansions, and Faxén's laws of force, torque, and stresslet for slip particle are also derived. The solutions of two-body problem are confirmed to recover the existing results in the no-slip limit and for the case of equal scaled slip lengths.

cond-mat.stat-mech↗

arXiv1997

Behavior of fluidized beds similar to equilibrium states

Systematic simulations are carried out based on the model of fluidized beds proposed by the present authors [K.Ichiki and H.Hayakawa, Phys. Rev. E vol.52, 658 (1995)]. From our simulation, we confirm that fluidization is a continuous transition. We also confirm the existence of two types of fluidized phases, the channeling phase and the bubbling phase. We find the close relations between the averaged behaviors in fluidized beds and quasi equilibrium states in dense liquids. In fluidized beds, (i) the flow rate plays the role of the effective temperature, and (ii) the existence of a kind of the fluctuation-dissipation relation is suggested.

cond-mat.stat-mech↗

arXiv1995

Hydrodynamic effects in density waves of granular flows

Granular flows in a narrow pipe are studied numerically by the model taking account of hydrodynamic effects of fluid surrounding particles. In the simulations density waves are observed over the wide range of the Stokes number, which represents the inertial effect of particles. The mechanisms of formation of the density waves are considered and two types of density waves, which are observed in the systems with zero and finite Stokes numbers, are presented. Power spectra of density waves obtained from the simulations with non-zero Stokes number show $1/f^α$ power law which is similar to that in experiments.

adap-org↗

arXiv1995

Dynamical Simulation of Fluidized Beds --- Hydrodynamically Interacting Granular Particles

A numerical simulation of a gas-fluidized bed is performed without introduction of any empirical parameters. Realistic bubbles and slugs are observed in our simulation. It is found that the convective motion of particles is important for the bubbling phase and there is no convection in the slugging phase. From the simulation results, non-Gaussian distributions are found in the particle velocities and the relation between the deviation from Gaussian and the local density of particles is suggested. It is also shown that the power spectra of particle velocities obey power laws. A brief explanation on the relationship between the simulation results and the Kolmogorov scaling argument is discussed.

chao-dyn↗

arXiv1995

Statistical Theory of Sedimentation of Disordered Suspensions

An analytical treatment for the sedimentation rate of disordered suspensions is presented in the context of a resistance problem. From the calculation it is confirmed that the lubrication effect is important in contrast to the suggestion by Brady and Durlofsky (Phys.Fluids Vol.31, 717 (1988)). The calculated sedimentation rate agrees well with the experimental results in all range of the volume fraction.

adap-org↗