抄録
Microscopic manipulation of fluid dynamic systems on the basis of micro-TAS or Lab on a Chip has been attracting much attention. When the spatio-temporal scale of interest is small and the suspended object in fluid has a characteristic length scale of 1 micro meter or even less, the Brownian motion due to the thermal fluctuation plays an essential role in the dynamics. The macroscopic view of the Brownian motion of solute particles in solution often reduces to the diffusion phenomena described as the spatio-temporal evolution of the solute concentration field. However, when the dynamics of a single Brownian particle in solution is important, it is desired to be treated in the explicit manner on the single particle level. We study the dynamics of solute particle in fluid by the fluctuating lattice Boltzmann method (FLB). The FLB is a kind of lattice Boltzmann method (LBM), which takes into account the thermal fluctuation of the fluid in the systematic manner in the spatio-temporal evolution of the fluid dynamics in the framework of distribution function. The interaction between the solute particle and the fluid is described by the frictional coupling through relative velocity and friction coefficient in the similar manner to the Langevin equation. We define a prolate solute particle by the dumbbell model and analyze its orientation dynamics when subject to the solution flow through the parallel plates. The effect of thermal fluctuation is examined by comparison with the system with different diffusion coefficients.
