Session1: River Engineering and Management
Title: INFLUENCE OF BASSET HISTORY FORCE ON PREFERENTIAL CONCENTRATION OF SMALL PARTICLES AND BUBBLES IN TURBULENCE
Satoshi Yokojima, Yoshiaki Shimada, Kazuki Mukaiyama
Computation of the Basset history force can be very expensive, and hence, in past studies, either the whole part or some fraction of the history has been neglected even in the cases where its contribution may be important. Here the effects of the Basset history force on preferential concentration of small particles in a homogeneous isotropic turbulence under a wide range of the particle-to-fluid mass density ratio (from 0 up to 10000) 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). Compared with the traditional window method where the Basset integral is evaluated only over the latest period of size twin, the method of van Hinsberg that approximates the tail of the Basset force kernel by exponential functions is found to give a better result by using a much shorter (typically, two-order-of-magnitude smaller) twin. It is clearly revealed that the presence of the Basset force weakens the level of preferential concentration to some extent, especially under the conditions of the mass density ratio of around 1.5 − 10 for heavy particles and smaller than 0.7 for light particles.