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Kazuhiro Hara

Publications and source records attributed to Kazuhiro Hara.

3 recordsLinked to original sources

Discontinuous shear thickening of a moderately dense inertial suspension of hydrodynamically interacting frictionless soft particles

We demonstrate that discontinuous shear thickening (DST) can occur even in moderately dense, inertial suspensions of hydrodynamically interacting, frictionless soft particles. Using the Lubrication-Friction Discrete Element Method, our simulations reveal that DST can emerge at lower particle densities, provided that both the inertia of the suspended particles and their softness are sufficiently pronounced. Furthermore, we show that, under these conditions, the DST behavior obtained from the simulation qualitatively agrees with that predicted by kinetic theory, even without accounting for hydrodynamic interactions. These findings expand the understanding of DST in soft particle systems and highlight the importance of particle inertia and softness in controlling rheological behavior.

cond-mat.soft

Kinetic theory of discontinuous shear thickening of a moderately dense inertial suspension of frictionless soft particles

We demonstrate that a discontinuous shear thickening (DST) can take place even in a moderately dense inertial suspension consisting of frictionless soft particles. This DST can be regarded as an ignited-quenched transition in the inertial suspension. An approximate kinetic theory well recovers the results of the Langevin simulation in the wide range of the volume fraction without any fitting parameters.

cond-mat.soft

Relaxation with long-period oscillation in defect turbulence of planar nematic liquid crystals

Through experiments, we studied defect turbulence, a type of spatiotemporal chaos in planar systems of nematic liquid crystals, to clarify the chaotic advection of weak turbulence. In planar systems of large aspect ratio, structural relaxation which is characterized by the dynamic structure factor exhibits a long-period oscillation that is described well by a combination of a simple exponential relaxation and underdamped oscillation. The simple relaxation arises as a result of the roll modulation while the damped oscillation is manifest in the repetitive gliding of defect pairs in a local area. Each relaxation is derived analytically by the projection operator method that separates turbulent transport into a macroscopic contribution and fluctuations. The analysis proposes that the two relaxations are not correlated. The nonthermal fluctuations of defect turbulence are consequently separated into two independent Markov processes. Our approach sheds light on diversity and universality from a unified viewpoint for weak turbulence.

cond-mat.soft