The
Liutex
based
vortex
identification
method
is
superior
to
previous
methods
in
that
it
overcomes
the
issues
of
threshold
problem,
shear
contamination,
etc.,
with
a
clear
physical
meaning
direction
vector
represents
local
axis
rotation,
while
magnitude
equal
twice
angular
velocity
rigid-rotation
part
flow.
current
study
focuses
on
interaction
between
represented
rotation
and
residual
during
development
Λ
hairpin
boundary
layer
transition.
temporal–spatial
evolution
typical
vortical
structures
are
analyzed
Liutex–shear
decomposition
particular
attention
paid
position
strength
changes
shear.
Vortex
core
lines
extracted
investigate
mutual
interactions
inside
vortices.
It
demonstrated
for
vortex,
spanwise
rotating
motions
formed
at
head
region
can
persist
long
time
under
influence
surrounding
shear,
tail
stretches
down
near
wall
but
then
becomes
weaker
due
dissipation.
High-shear
regions
tend
be
located
top
or
below
When
legs
gets
stronger,
will
rolled
up
form
new
On
one
hand,
together
newly
consist
which,
turn,
leads
generation
second-
third-level
other
also
generates
many
smaller
streamwise
vortices
region.
results
show
very
important
The
difference
in
the
governing
equation
between
inviscid
and
viscous
flows
is
introduction
of
terms.
Traditional
Navier–Stokes
(NS)
equations
define
stress
based
on
Stokes’s
assumptions.
In
NS
equations,
supposedly
proportional
to
strain,
both
strain
tensors
are
symmetric.
There
several
questions
with
which
include
following:
1.
Both
symmetric
shear
terms
stretching
coordinate-dependent
thus
not
Galilean
invariant.
2.
physical
meaning
diagonal
off-diagonal
elements
clear,
coordinate-dependent.
3.
It
hard
measure
quantitatively,
viscosity
really
measured
by
vorticity,
strain.
4.
no
vorticity
tensor
plays
an
important
role
fluid
flow,
especially
for
turbulent
flow.
newly
proposed
dynamics
use
only,
anti-symmetric.
advantages
anti-symmetric,
invariants
independent
coordinate
rotation.
anti-symmetric
stress.
Viscosity
coefficients
obtained
experiments,
vorticity.
term
can
be
further
decomposed
into
rigid
rotation
shear,
turbulence
research.
5.
computation
cost
reduced
half
as
all
zero
six
three.
Several
computational
examples
tested,
clearly
demonstrate
new
have
exactly
same
results.
As
shown
below,
identical
mathematics,
but
one
has
lower
mentioned
above,
including
possibility
study
flow
better.
recommended
instead
equations.
unique
definition
operation
vectors
matrix
also
discussed
this
paper.
Machines,
Год журнала:
2021,
Номер
9(12), С. 353 - 353
Опубликована: Дек. 15, 2021
Vortex
pumps
have
good
non-clogging
performance
owing
to
their
impellers
being
retracted
into
retraction
cavities,
but
they
are
much
less
efficient
than
ordinary
centrifugal
pumps.
In
this
paper,
numerical
simulations
were
performed
on
a
model
of
the
150WX200-20
vortex
pump
for
four
different
blade
types,
and
influence
structure
was
determined.
The
revealed
existence
axial
vortices
in
flow
passage
between
blades
impeller
region.
geometric
characteristics
these
more
regular
two-phase
solid-liquid
single-phase
liquid
flow.
presence
solid
phase
reduced
strength
compared
with
suppressed
increase
size
secondary
circulation
vortex.
It
found,
however,
that
shape
had
greater
circulating
phase.
state
medium
flowing
out
domain
direct
effect
related
law
governing
channel
blades.
found
front-bent
best
curved
worst.
This
type
internal
used
further
explain
relationship
external
pump,
understanding
which
is
crucial
selection
hydraulic
optimization.
International Journal of Heat and Mass Transfer,
Год журнала:
2019,
Номер
144, С. 118590 - 118590
Опубликована: Сен. 6, 2019
The
thermal
turbulence
in
an
infinitely-long
square
annular
duct
(SAD)
was
studied
by
the
direct
numerical
simulation
with
Reynolds
(Re)
number
Reb≈6400
based
on
bulk
velocity.
isothermal
boundary
condition
applied
to
side
walls
SAD
higher
and
lower
temperatures
outer
inner
walls,
respectively.
As
one
of
most
fascinating
features
for
corner
turbulence,
turbulent-driven
secondary
flow
(TDSF)
presented
twin
counter-rotating
vortex
pairs
symmetrically
located
at
concave
convex
corners.
TDSF
found
significantly
increase
spatially-averaged
Nusselt
(Nu)
comparing
laminar
flow.
instantaneous
structures
were
visualized
third-generation
vortex-identification
method
Liutex.
budget
analyses
governing-equation
turbulent
layer
(TBL)
distinguished
balancing
mechanisms
from
traditional
flat-plate
TBL,
which
justified
necessity
classify
generic
TBLs
into
their
sub-categories
Type-A,
B
C
TBLs.
Moreover,
current
study
focused
a
issues
such
as
effects
TBL
law
formulations.
For
present
SAD,
it
that
buffer
between
semi-log
layers
tended
be
wider
than
linear
conduction
was,
first
time,
Type-B
temperature
TBL.
Based
indicator
function,
quantitative
sublayer
partitions
conducted
both
velocity
then
applicable
ranges
sublayers
rigorously
determined.
Further,
profound
damping
mechanism
introduced
laws
derive
more
accurate
analytical
formulations
entire
sublayers.
