2019 年 85 巻 871 号 p. 18-00476
In the present study, we have analyzed the flow field around a cube in a Stokes flow regime in order to estimate the diffusion coefficients of cube-like particles that are required for performing Brownian dynamics simulations of a cubic particle suspension. The main results obtained here are summarized as follows. In the situation of a uniform flow field with a Reynolds number sufficiently smaller than unity, the force acts on the cube only in the flow field direction, and the torque does not act on the cube. Therefore, the uniform flow does not induce the rotational motion of the cube. In the situation of a rotational flow field with a sufficiently low Reynolds number, the torque acts on the cube only in the direction of angular velocity of the rotational flow field, and the force does not act on the cube. This implies that the translational motion of the cube is not induced due to the rotational flow field. These characteristics are in good agreement with those for the case of spheres in a Stokes flow situation. From these results, we may conclude that the diffusion coefficients of the cube-like particles can be expressed by applying a correction factor to those of the spherical particles. Moreover, we understand that the translational and the rotational motion of a cube are not coupled in the condition of the flow filed with a low Reynolds number sufficiently smaller than unity. Furthermore, in Brownian dynamics simulations, the equations of translational and rotational motion of cube-like particles can be treated in the same way as the spherical particles by applying the correction factor.
