A modified laser-Doppler velocimetry method is utilized to measure
fully developed
particle velocity and concentration profiles, as well as the mean-square
amplitudes of
velocity fluctuations (i.e. one component of the so-called particle temperature),
for
concentrated monodisperse suspensions across the narrow gap of a rectangular
channel. A stable index-of-refraction match of the suspending and particulate
phases
in conjunction with short-focal-length focusing optics has enabled data
acquisition up
to particle volume fractions of 0.50. In general, the particle concentration
distributions
possess a maximum near the channel centreline and a minimum at the channel
walls.
Coupled to these concentration distributions were blunted velocity profiles,
and
particle velocity fluctuation distributions that had a sharp maximum at
gap positions
approximately 80% of the way from the channel axis towards the walls. The
particle
velocity distributions were consistent with the absence of slip between
particles and the
suspending fluid.The experimental data were compared with theoretical predictions from
the diffusive
flux model (Leighton & Acrivos 1987; Phillips et al. 1992),
a model due to Mills & Snabre (1995), and the suspensions balance model
(McTigue & Jenkins 1992; Nott & Brady 1994). The influence of
bulk particle concentration, suspension volumetric flow
rate, and ratio of channel gap width to particle diameter on the fully
developed profiles
was qualitatively consistent with the theoretical predictions from all
three models. For
the diffusive flux and suspension balance models, we used both literature
values for
model parameters, and values obtained from a best fit to our entire set
of experimental
data. Overall, the Mills & Snabre and suspension balance models were
found to
provide a better quantitative fit to the experimental data than the diffusive
flux model.
Estimating Tumor Vascular Permeability of Nanoparticles Using an Accessible Diffusive Flux Model
