RESEARCH
August-September 2014 | Desalination & Water Reuse | 47 |
Figure 4. Flow patterns in the pilot DAF
For three-dimensional flow
profiling, a Nortek Vectrino
ADV with a cable-mounted
three-dimensional, side-looking
probe (figure 2) was used
in this study. For seawater
application, 316-grade
stainless steel was selected as
a probe material. It is clear that
proper positioning of the ADV
probe was a critical factor in
measuring three-dimensional
vector flows.
To avoid any unfavorable
flow hindrance due to the
use of the probe in confined
vertical channels in a DAF
tank, the entire probe body
was fixed on supporting rods
with clamps to maintain its
position.
To measure flow characteristics,
153 sampling points were
carefully assigned in an x, y,
and z coordinate system for
the bench DAF tanks while
203 points were assigned in
the pilot-scale tanks. It was
assumed x- and y-directional
flows on the left and right
side from the centre line of
the DAF tank was bilaterally
symmetrical in a y-directional
symmetric DAF tank.
The flow velocity and
direction at each point in the
contact zone, separation zone,
and effluent chamber was
measured using ADV.
The velocimeter was tuned
to measure the lowest velocity
range that could be provided
by its manufacturer while
maintaining high accuracy.
Velocity measurement data
at each sampling point was
recorded as a binary velocity
file at least 30 seconds after a
two minutes stabilization time.
Then, from velocity data and
averaged x-, y-, z- directional
velocity, an averaged
magnitude of three-dimensional
vectors was calculated.
Figure 5. Flow patterns in the separation zone
Front view Rear view Side view
ADV sampling
method
y
x
