(537h) Simulation of Concentrated Suspensions in Free Surface Systems

Simulation
of concentrated suspensions in free surface systems

Mahyar Javidi¹,
Andrew N. Hrymak²

Department of Chemical and Biochemical Engineering, Western
University, London, ON, Canada

Corresponding author: mjavidis@uwo.ca

Keywords: coating, film, suspension, solid particle

Particle-laden flows are important in
a wide range of industrial fields, such as oil and gas refinment, waste water
treatment, paper manufacturing, biological and polymer processes where transport
and manipulation of suspensions occur [1, 2]. In addition, the capability of
developing a thin uniform layer of suspensions with evenly distributed
particles is essential in many applications. In coating processes of
suspensions, the particle distribution pattern can enhance the performance of
the final product by changing the bulk and surface characteristics. In this
work, the behavior of suspensions in a dip/free coating process is
investigated. Specifically, the adherence of a thin film on a substrate surface
in vertical withdrawal from a pool of liquid with dispersed solid particles.

In the current study, the dynamics of
concentrated suspension flow modeled based on the density of solid particles in
the system, where macroscopic methods used for tracking the volume fraction of
particles in the flow. In modeling procedure of dispersions in dip
coating, a nonlinear constitutive equation of Phillips et al. [3] for the
particles distribution in suspensions coupled with Volume of Fluid method [4]
for capturing the free surface. The model incorporated into a finite volume
method formulation to simulate shear-induced particle migration in
non-homogenous shear flows of suspensions in dip coating process.

Numerical
simulation enables one to predict the film thickness and validate with
experimental results in a range of solid particle volume concentration from 0.1
to 0.4 and withdrawal velocities of 5-15 cm/s. Simulation of free coating for a
cylindrical substrate (fiber, wire) in the dispersions can be seen in Fig. 1.
In this picture, the solid particle distribution is shown in a dip coating
system for the initial volume fraction of 0.4 of particles.

Fig. 1. Dip coating for monodisperse solid particles in the flow ?
pictures a to c illustrates the simulation of finite length substrate withdrawn
out of coating vessel  

The numerical simulation for dip coating process
has been developed in three dimensions for dispersions and a finite length
cylinder has been used as a coating substrate. For this work, the moving mesh
method is applied where the substrate and mesh moves with the withdrawal
velocity. The zero gradient boundary condition has been set for the base of the
coating bath and wall condition with the fixed value of zero velocity has been
set for the bath wall.  This work investigates a simulation approach to investigate
suspension flows and to identify possible limitations and solutions within this
simulation methodology.

References

1.   N. Murisic, J. Ho, V. Hu, P. Latterman, T. Koch,
K. Lin, M. Mata & A.L. Bertozzi, J. Phys D 240, 1661-1673(2011)

2.   S. R. Subia, M. S. Ingber, L. A. Mondy, S. A.
Altobelli & A. L. Graham, J. Fluid Mech 373, 193-219 (1998)

3.   R.J. Phillips, R. C. Armstrong, R. A. Brown, A.
L. Graham & J. R. Abbott, Phys Fluids A 4, 30-40 (1992)

4. C. W. Hirt, B. D. Nicols, J. Comp. Phys. 39, 201-225 (1981)