[P1-81] Dynamics of a Polymer in Bulk Solution under Shear Flow
This study describes dynamics of viscosity index improver (VII) in bulk lubricants under shear flow. Small amount of polymer named VII is added in basis oil to control viscosity index (VI) which is a parameter to express temperature dependence of viscosity. Controlling VI is one of the commonly used methods to improve the fuel consumption of motor vehicles. Here we simulate the dynamics of polymer under shear flow in Bulk Solution. Polymer segment is modeled as sphere Brownian particle. The motion of the particle is tracked by the Langevin equation, whereas the Navier-Stokes equation governing the behavior of the base oil is analyzed by using the lattice Boltzmann method. The two equations are coupled through the friction between the particle and the fluid. The friction force is in proportion to the velocity of a particle relative to the host fluid, which is evaluated locally based on the velocity difference at the position of the point particle. The friction force acting on a particle is estimated by fitting the analytical solution or the flow around a Stokes-let to the flow field obtained numerically. The reaction force acts on the position of the particle, which realizes two-way coupling between the particle and fluid motions. The lattice Boltzmann method is employed for the flow simulation, which is compatible with massive parallel computing, and is easy to apply various types of boundary conditions. In order to simulate the system, the computational domain has three-dimensions and Periodic boundary condition. External forces are introduced to form simple shear flow. The dynamics of polymer in shear flow is examined by using two computational methods.