微小粒子・気泡のクラスタ形成に対するバセット履歴力の影響について

抄録

Computation of the Basset history force depending on the time history of the relative acceleration between the particle and the fluid at the particle location is very expensive, and hence, in past studies, either the whole part or some fraction of the history has been neglected. Here the effects of the Basset history force on preferential concentration of small particles in a homogeneous isotropic turbulence under a wide range of mass density ratio have been investigated by direct simulations of the Navier-Stokes equations. The Basset force is numerically approximated by the method of van Hinsberg et al. (J. Comput. Phys. 230 (2011) 1465). While the method is found to be fast and accurate, the results obtained from the traditional method taking account of the contributions only over the latest period of a time scale t_win shows a high dependence on t_win. It is clearly revealed that the presence of the Basset force weakens the level of preferential concentration, especially under the conditions of the mass density ratio γ of around 1.5–10 for heavy particles and γ smaller than 0.7 for light particles.