Combustion Science and Technology,
Год журнала:
2022,
Номер
196(9), С. 1410 - 1431
Опубликована: Авг. 31, 2022
Despite
more
than
a
decade-long
effort
to
understand
the
flow
structure
in
Inverse
Jet
flame
(IJF)
configuration,
performance
enhancements
on
such
configurations
are
sparsely
investigated.
A
passive
technique
improve
air-fuel
entrainment
IJF
configuration
is
implemented
this
study
by
altering
central-air
port
geometry
with
an
elliptical
port.
The
and
mixing
characteristics
studied
using
three-dimensional
Favre-averaged
method
for
central
air-port
compared
its
circular
counterpart.
numerical
model
validated
standard
k-ε
turbulence
capture
complex
physics
comprehend
of
burner
configuration.
brought
differences
spreading
rates.
present
work
emphasizes
dynamics
characteristics,
including
features
recirculation
zone,
kinetic
energy,
velocity
distribution.
(omega)
Ω
vortex
identification
turbulent
energy
distribution
provided
profound
insights
into
role
structures
mixing.
prominent
novel
counterpart,
thus
affecting
structure.
strength
was
found
be
0.94
0.88
IJF.
This
further
quantifies
enhanced
as
observed
inverse
jet
diffusion
based
mixture
fraction
index,
which
can
applied
any
configurations.
index
at
axis
switching
location
greater
80%
45%
Journal of Turbomachinery,
Год журнала:
2023,
Номер
146(3)
Опубликована: Окт. 27, 2023
Abstract
Corner
separation
is
an
inherently
unsteady
flow
feature
in
axial
compressor
cascade,
and
it
significantly
affects
the
aerodynamic
performance
of
compressors.
The
field
a
highly
loaded
cascade
at
Mach
number
0.59
under
moderate
condition
simulated
based
on
delayed
detached
eddy
simulation.
Comparisons
averaged
transient
show
that
three-dimensional
corner
composed
fine-scale
vortex
structures.
classical
recognition
structures
consequence
time-averaging.
To
better
understand
contribution
to
structures,
evolutions
fields
time
series
power
spectrums
are
analyzed.
A
dominant
periodic
fluctuation
caused
by
development
separating
vortices
with
characteristic
frequency
around
3500
Hz
or
Strouhal
0.75.
Further,
energy
scales
spatiotemporal
features
these
behaviors
analyzed
using
proper
orthogonal
decomposition
dynamic
mode
methods.
Results
low-frequency
mainly
passage
lower-span
regions
govern
large-scale
changes
size
intensity
act
certain
intermittency.
developing
prevails
higher
affected
concentrated
shedding
vortex.
As
dissipate
approaching
midspan,
effect
velocity
reduced,
although
dominates
pressure
good
stability
whole
passage.
Proceedings of the Institution of Mechanical Engineers Part A Journal of Power and Energy,
Год журнала:
2025,
Номер
unknown
Опубликована: Апрель 10, 2025
To
investigate
the
spatiotemporal
characteristics
of
vortex
structures
within
a
centrifugal
pump
and
explore
application
modal
decomposition
techniques
in
three-dimensional
feature
extraction,
this
study
employs
computational
fluid
dynamics
(CFD)
to
numerically
simulate
unsteady
flow
under
rates
80
m
3
/h
(low-flow
condition),
100
(design
120
(high-flow
condition).
By
integrating
Omega-Liutex
method
with
techniques,
including
Proper
Orthogonal
Decomposition
(POD)
Dynamic
Mode
(DMD),
detailed
characterization
is
performed.
The
results
indicate
that,
compared
other
identification
criteria,
technique
effectively
captures
pump.
applying
POD
analyze
impeller
region
three
different
conditions,
analysis
revealed
that
tip
vortices
wake
dominate
energy
distribution
across
all
an
proportion
ranging
from
34.7%
40.3%.
Additionally,
both
low-flow
design-flow
first
second-order
demonstrate
periodic
behavior.
dominant
volute
exhibit
significant
variations
conditions.
Under
primary
include
tongue-shedding
wall-attached
vortex,
nonlinear
interaction
observed
between
modes.
high-flow
energetic
structure
recirculating
diffuser
section.
A
comparison
areas
for
modes
regions
conditions
reveals
mode
exhibits
smallest
area.
first-order
obtained
through
DMD
clearly
overall
Among
four
modes,
there
are
always
two
exhibiting
identical
structures.
In
can
identify
large-scale
relatively
low
regions,
whereas
extracts
more
comprehensively.
In
order
to
reveal
the
effect
of
baffles
on
flow
structure
and
cyclic
variation
stirred
by
Rushton
turbines,
particle
image
velocimetry
experiments
were
performed
in
baffled
unbaffled
tanks.
a
tank,
peak
value
time-averaged
velocity
obviously
increases,
high
region
enlarges
significantly,
fluctuation
fluid
elements
near
turbine
increases
significantly.
20°
phase
plane
swirl
strength
slightly
enlarges,
but
phase-resolved
is
lower.
The
regions
turbulent
kinetic
energy
are
larger
tank
at
various
planes.
Using
quadruple
proper
orthogonal
decomposition,
field
decomposed
into
small-scale
part,
transition
large-scale
mean
part
with
different
spatial
scales.
Adding
baffle,
largest
scale
(it
favorable
for
mass
transfer
liquid
levels)
which
mainly
includes
random
cascade,
enhances
conducive
diffusion).
main
influence
blade
passages
large-scale,
standard
deviation
time
coefficients
decreases
3%–4%
adding
baffle.
Journal of Marine Science and Engineering,
Год журнала:
2024,
Номер
12(1), С. 148 - 148
Опубликована: Янв. 12, 2024
Predicting
the
flow
situation
of
cavitation
owing
to
its
high-dimensional
nonlinearity
has
posed
great
challenges.
To
address
these
challenges,
this
study
presents
a
novel
reduced
order
modeling
(ROM)
method
accurately
analyze
and
predict
fields
under
different
conditions.
The
proposed
ROM
decomposes
field
into
linearized
low-order
modes
while
maintaining
accuracy
effectively
reducing
dimensionality.
Specifically,
focuses
on
predicting
Clark-Y
hydrofoil
using
combination
numerical
simulation,
proper
orthogonal
decomposition
(POD),
neural
networks.
By
analyzing
conditions,
results
revealed
that
POD
reduces
cavity
achieving
excellent
reconstruction.
Notably,
zeroth-
first-order
are
associated
with
attachment
cavitation,
second-,
third-
fourth-order
correspond
shedding.
Additionally,
fifth-
sixth-order
along
surface
backward
jet
flow.
conditions
high-energy
modes,
network
proved
be
more
effective,
exhibiting
performance
in
stable
attached
cavitation.
However,
for
cloud
model
requires
further
improvement.
This
not
only
introduces
approach
but
also
highlights
new
challenges
will
require
continuous
attention
future
research
endeavors.
Journal of Fluid Mechanics,
Год журнала:
2024,
Номер
980
Опубликована: Фев. 8, 2024
Helicity
plays
a
key
role
in
the
evolution
of
vortex
structures
and
turbulent
dynamics.
The
helicity
dynamics
streamwise-rotating
channel
turbulence
are
discussed
this
paper
using
budget
equation
differentiated
second-order
structure
function
helicity.
Generally,
rotation
Reynolds
numbers
exhibit
opposing
effects
on
interscale
vortices.
Under
buffer
layer,
positions
peaks
proportional
to
ratio
between
numbers.
mechanism
is
related
convection
rotation.
Rotation
directly
affects
balance
through
Coriolis
term
corresponding
pressure
term.
In
scale
negative
at
small
scales
but
positive
large
scales,
which
mainly
induced
by
spatial
(the
production
convection)
reduced
cascades.
Examination
reveals
close
association
streaks,
with
streak
lift
angles
exhibiting
an
increase
decrease
log-law
terms
remain
independent
forward
cascaded
towards
scales.
spanwise
vortices
layer
sweep
events
Our
findings
indicate
that
these
suppressed
recover
increasing
numbers,
aligning
observed
balance.
Energies,
Год журнала:
2021,
Номер
14(22), С. 7626 - 7626
Опубликована: Ноя. 15, 2021
The
inter-blade
passage
vortex,
the
vortex
rope
of
draft
tube,
and
in
guide
apparatus
are
characteristics
flow
instability
Francis
turbine,
which
may
lead
to
fatigue
failure
serious
cases.
In
current
study,
order
accurately
capture
transient
turbulent
under
different
conditions
fully
understand
field
structure,
we
conduct
a
simulation
that
adopts
sliding
grid
technology
large-eddy
(LES)
method
based
on
wall-adapting
local
eddy
viscosity
(WALE)
model.
Using
pressure
iso-surface
method,
Q
criterion,
latest
third-generation
Liutex
identification
this
study
analyzes
compares
outflow
apparatus,
focusing
ability
information
by
various
methods
unique
structure
condition
small
opening.
results
indicate
dependence
threshold
is
small,
scale
range
direction
captured
wider,
but
spanwise
relatively
weak.
smaller
opening,
more
disorderly
vortexes
generated
each
component
unstable
field.
original
shape
destroyed
due
interaction
between
vortexes.
Under
an
generated,
affecting
efficient
stable
operation
turbine.
