DNS investigation of the dynamical behaviour of trailing vortices in unbaffled stirred vessels at transitional Reynolds numbers
File(s)
Accepted version
Author(s)
Basbug, S
Papadakis, G
Vassilicos
Type
Journal Article
Abstract
Flow in an unbaffled stirred vessel agitated by a four-bladed radial impeller is investigated by using
direct numerical simulations at
Re
= 320 and 1600. We observe fluctuations in the power consumption
with a peak frequency at ca. three times the impeller rotational speed for both Reynolds numbers. It
is discovered that these fluctuations are associated with a periodic event in the wake of the blades,
which involves alternating growth and decay of the upper and lower cores of the trailing vortex pair
as well as up-and-down swinging motion of the radial jet. Moreover, the phase relation between the
wakes of the different blades is examined in detail. Further studies using fractal-shaped blades show
that the exact blade shape does not have a strong influence on this phenomenon. However, the wake
interaction between the blades, hence the number of blades, has a direct influence on the unsteadiness
of trailing vortices.
direct numerical simulations at
Re
= 320 and 1600. We observe fluctuations in the power consumption
with a peak frequency at ca. three times the impeller rotational speed for both Reynolds numbers. It
is discovered that these fluctuations are associated with a periodic event in the wake of the blades,
which involves alternating growth and decay of the upper and lower cores of the trailing vortex pair
as well as up-and-down swinging motion of the radial jet. Moreover, the phase relation between the
wakes of the different blades is examined in detail. Further studies using fractal-shaped blades show
that the exact blade shape does not have a strong influence on this phenomenon. However, the wake
interaction between the blades, hence the number of blades, has a direct influence on the unsteadiness
of trailing vortices.
Date Issued
2017-06-01
Date Acceptance
2017-05-01
Citation
Physics of Fluids, 2017, 29
ISSN
1089-7666
Publisher
AIP Publishing
Journal / Book Title
Physics of Fluids
Volume
29
Copyright Statement
© 2017 The Authors. Published by AIP Publishing. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Physics of Fluids and may be found at http://aip.scitation.org/doi/abs/10.1063/1.4983494?af=R
Subjects
Fluids & Plasmas
01 Mathematical Sciences
02 Physical Sciences
09 Engineering
Publication Status
Published
Article Number
064101