Masato Makino

Simulation of DNA motion in a microchannel using stochastic rotation dynamics

The authors propose a method to simulate the DNA motion in microchannels of complex geometry. It is based on stochastic rotation dynamics using a new scheme for the boundary condition. The method enables them to define a boundary wall of arbitrary shape and to describe a wall moving at an arbitrary velocity. As an application, they simulate the motion of DNA in Poiseuille flow between two parallel planes and show that DNA molecules tend to concentrate near the center of the channel in agreement with experimental results.

Migration of twisted ribbon-like particles in simple shear flow

The motion of rigid twisted ribbon-like particles in shear flow is studied by computer simulation. It is shown that the twisted ribbon migrates in the vorticity direction in strong shear flow with the sign determined by the chirality: the right-handed particles and their mirror-imaged particles move in opposite directions. This enables the separation of chiral particles from the racemic mixture. The average migration velocity in the vorticity direction is studied as a function of the shear rate, the length, and the pitch of the particle.

Brownian Motion of a Particle of General Shape in Newtonian Fluid

We give a general formulation of handling the Brownian motion of a rigid particle of arbitrary shape in a Newtonian fluid subject to external force, torque and velocity field. We show how to includ...

Sedimentation of particles of general shape

When a set of complex shaped particles settles down under gravity, they will generally spread in vertical and horizontal directions even though there is no thermal motion since the velocity of complex shaped particle is not in the direction of gravity and depends on the initial orientation. We study the relationship between the dispersion behavior and the particle characteristics. It is shown by theory and simulation that the dispersion behavior can have various types depending on whether the particle is skewed or not or whether the gravity gives a torque or not. The conditions for these cases to happen is discussed and its validity is demonstrated by computer simulation.

Interference Effects in the Drying of Polymer Droplets on Substrate

Drying processes of many droplets of polymer solution placed on a solid substrate are studied numerically. A coupled equations for the flow of liquid in the droplets and the diffusion of solvent in the air are solved simultaneously. It is shown both numerically and theoretically that the evaporation rate of droplets interferes strongly and that the final shape of the deposit left on the substrate depends stronlgy on the arrangement of the droplets.

Sedimentation of a Particle with Translation–Rotation Coupling

We present an analysis on the sedimentation of a propeller-like particle in Newtonian fluid. Due to the translation–rotation coupling, the propeller-like particle settles down with nonconstant spee...

Passage of a Small Air Bubble through a Circular Pore across the Plate of Finite Thickness

Experimental and theoretical studies are made on the passage of a small air bubble through a circular pore of finite length which connects two half-space chambers of viscous fluid, with an application to the transport of a drug-containing particle to a diseased cell through a cleft of endothelial cells in mind. Dependences of the change of shape and the translational velocity of the bubble on the deformability and the constriction size are examined.

Electrokinetic boundary condition compatible with the Onsager reciprocal relation in the thin double layer approximation

The boundary condition, which has been used in the conventional electrokinetic calculation in the thin double layer approximation, has a flaw that it does not give the Onsager reciprocal relation for the sedimentation of charged particle. We propose a new boundary condition, which satisfies the reciprocal relation, and derive a general form for the mobility matrix for the motion of a charged particle under the action of external force, torque, and electric field. We then calculate the mobility matrix explicitly for homogeneously charged spherical particle and discuss the effect of the surface slippage and the surface conductivity on the particle mobility and electric conductivity.

Viscoelasticity of Dilute Solutions of Particles of General Shape

We present a theory to calculate the viscoelasticity of dilute suspensions of particles of general shape. We give a formula for the dynamic viscosity expressed in terms of the mobility tensors. We study the viscoelasticity of propeller-like particles which consist of two disks and thin-rod. The non-linear viscoelasticity and the normal stresse differences of the propeller-like particles are calculated by computer simulation.

Anomalous Orientation of Dipolar Particle in Shear and Magnetic Field

We found, by numerical simulation, an anomalous behavior in the average magnetic moment of a dilute suspension of magnetic particles of elongated shape under shear flow. In a shear flow \(\mathbf{v...