The Dorr-Oliver Flotation cell

1
The Dorr-Oliver Flotation cell
Six blade impeller
Stator with 4 large blades and 12 small
2
The three studied Configurations for Re35000
y
x or r
1cm
3cm
1cm with stator
3
Normalized velocity magnitude contours
In the first case two recirculation regions are
observed while in the last we have only one
The stagnation points have moved from the
inclined wall closer to the bottom of the tank
4
Normalized radial velocity contours
The radial jet is more energetic in the case
where the impeller is further up. The more flow
comes in from the bottom the more will come
out The case with the stator has the smallest
radial component because it is Blocked in the
periphery too
5
Normalized TKE contours
With a flat disk blocking the return of the flow
on the top of the impeller and the ground
blocking the return form the bottom, the edges of
the impeller produce slower flow but much higher
levels of turbulence.
In the case where the stator is present even more
turbulence is generated due to the vortices that
form between the stator blades
6
Normalized Dissipation rate contours
For the case with the stator even if high values
of dissipation can be seen around the stator, the
maximum is observed inside the stator blades
7
Normalized Z-vorticity
In the first two cases two distinct recirculation
regions form while in the latter one small
structures seem to appear between the stator
blades and some inside the stator but clearly
smaller than in the other cases.
8
Streamlines along a horizontal plane of the
impeller at
In the second case an envelope of the streamlines
separating those that spiral inward from those
that spiral outward can be seen.
In the case with the stator, the fluid in its
effort to pass through the stator blades form
small vortices between them.
9
Y-vorticity along a horizontal plane of the
impeller at
In the first case vorticity is high around the
impeller blade where an extended vortex is
formed
In the second case small vortices are very close
to impeller blades and the second one starts
closer
In the last case high values of vorticity can be
observed everywhere due to the vortices that
form around the stator blades.
10
TKE along a horizontal plane of the impeller at
The first case has the lowest value of TKE The
second one has higher values because more
turbulence is generated In the last case the
flow finds more resistant, creates vortices
around the stator And higher values of TKE are
observed
11
Dissipation rate along a horizontal plane of the
impeller at
Similar conclusion with the ones for the TKE can
be drawn for the Dissipation rate
12
Streamlines along a horizontal plane of the
impeller at
In the first two cases some of the flow is
returning back from the two recirculation regions
next to the impeller while some of it is still
going out
In the case with the stator most of the flow is
returning back from the huge recirculation
region while some of it inside the stator still
tries to pass through.
13
Y-vorticity along a horizontal plane of the
impeller at
In the case with the stator, higher values are
observed next to rotor blades than in the stator
blades. This can be attributed to the fact that
now more flow is moving inward than outward and
therefore the impeller makes a bigger effort to
push the flow outside.
14
TKE along a horizontal plane of the impeller at
TKE for the first case increased while in the
second the opposite happened In the case with
the stator it decreased in the boundary of it but
increased in the area close to the rotor blades.
15
Dissipation rate along a horizontal plane of the
impeller at
Similar conclusion with the ones for the TKE can
be drawn for the Dissipation rate
16
Streamlines along a horizontal plane of the
impeller at
In the first two cases the envelope grows
because more flow is returning back to the
impeller.
In the last case in the lower part of the tank,
instead of sixteen stator blades there are only
four and therefore they do not block as much the
flow as at the higher elevations
17
Y-vorticity along a horizontal plane of the
impeller at
For the first two cases even smaller values of
vorticity are observed In the case with the
stator although there are not high values of
vorticity between the stator blades high values
are observed in the area of the impeller blades
18
TKE along a horizontal plane of the impeller at
Low values of TKE are dominated in the first two
configurations while in the one with the stator
higher values of TKE than before appear next to
the impeller blades.
19
Dissipation rate along a horizontal plane of the
impeller at
20
Conclusions

• The turbulent kinetic energy and dissipation have
  the highest values in the immediate neighborhood
  of the impeller
• Good agreement with the experimental data is
  succeed
• Most of the times the Standard k-e model predicts
  better the flow velocities and the turbulent
  quantities while in some others has poor
  performance and the RNG k-e is better
• In the case of the low configuration model
• there is a strong tendency to skew the contours
  downward
• the dominant downward flow is diverting the
  jet-like flow that leaves the tip of the impeller
  downward, and it convects with the turbulent
  features of the flow.
• The axial component of the velocity has high
  values

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Future Work

• Experimental predictions for the Dorr-Oliver
  Flotation cell
• Comparisons of the studied cases with the
  experiments
• More Re numbers and clearances for the
  Dorr-Oliver Cell
• Higher Re numbers for both Tanks (100000-300000)
• Unsteady calculations
• Extension to two-phase or three phase flows