A cyclone separator uses the centrifugal force produced
by a swirling flow to separate substances with the same
specific weight but different size. It has been widely
utilized in the refining process of powder materials.
However, the performance for separation is insufficient
for the separation accuracy required in the particle design
of the powder materials. It is thus necessary to develop
an advanced cyclone separator with high-accuracy particle
separation because the design based on the traditional
principle for separating large particles is probably
unavailable. In order to establish the attempt, it is very
essential to grasp the turbulent flow characteristics of
complicated swirling flows in the cyclone separator
because it is expected that the motion of small particles
is considerably influenced by fluctuations in the flow.
We devised an advanced tangential-type cyclone
separator, and have experimentally investigated the
turbulent characteristics of the swirling flows using the
cyclone model with simplified structure in order to make
clear the relation between the flow characteristics and the
particle separation[1~3]. In this paper, numerical simulation
of the swirling flows is performed. In previous numerical
study, Reynolds averaged numerical simulation (RANS)
has been applied to swirling flows in the cyclone
separator[4,5]. In such simulation, it is probably difficult
to predict unsteady phenomena peculiar to the swirling
flows in the cyclone separator such as oscillating motion
of vortex core and vortex breakdown. Moreover, it is
also reported that a standard model which is widely used
in RANS cannot accurately predict the flow characteristics
of swirling flows[6]. Therefore, we have proposed the
prediction method combined with the large eddy
simulation (LES) based on a Smagorinsky model[7] for
the flow field and the particle tracing with a Lagrangian
method. The validity of the method has been confirmed
through comparison with the experimental results[8]. In
this paper, we numerically investigate the particle
motions inside cyclone separators with a variety of the
height of inserted pipe, and discuss the influences on the
performance for particle separation.