|
From a numerical perspective, the rotation of the impeller relative
to the baffles poses a special problem when modeling stirred tanks.
The simplest solution is to adopt a "black-box" approach, where
the actual geometry of the impeller is not modeled but the velocity
profile of the impeller discharge, determined experimentally, is
prescribed.
|
A310 Impeller, Courtesy of LIGHTNIN
|
More advanced methods, which model the impeller geometry explicitly,
include the multiple reference frame (MRF) method and the sliding
mesh method. With both of these methods, the flow around the impeller
blades is modeled in detail, and no prescribed experimental data
is required. With the MRF method, one "snapshot" of the flow field
at one point in time during the impeller rotation is calculated.
|
With the MRF model, the solution in the impeller region is solved
in the rotating frame of the impeller.
|
|
With the sliding mesh method, the flow field is calculated as
a function of time, with the impeller actually rotating. The rotating
grid in the impeller region "slides" past the stationary grid in
the baffle region. The results of these models typically compare
well with experimental data.
|
Multiple impeller animation
|
