Physics of Fluids,
Год журнала:
2024,
Номер
36(10)
Опубликована: Окт. 1, 2024
Micro
vortex
generators
(mVGs)
control
cavitation
by
altering
the
boundary
layer
flow
structure.
This
study
employs
wall-adapting
local
eddy-viscosity
large
eddy
simulation
(WALE-LES)
turbulence
model
combined
with
Zwart–Gerber–Belamri
to
conduct
transient
numerical
simulations
on
National
Advisory
Committee
for
Aeronautics
0015
baseline
hydrofoil
and
equipped
mVGs
under
various
numbers.
The
proper
orthogonal
decomposition
method
experiments
verify
accuracy
consistency
of
these
regarding
cavity
scale.
elucidates
mechanisms
which
suppress
cloud
at
low
numbers
induce
high
Results
indicate
that
maintain
sheet
characteristics
numbers,
reducing
wall
pressure
fluctuations
enhancing
stability.
During
inception,
mVG-induced
leads
early
formation.
In
phase,
modal
energy
distribution
is
more
dispersed,
while
in
inception
concentrated
significant
dominant
modes.
Moreover,
counter-rotating
vortices
generated
mitigate
separation,
enhance
leading-edge
attachment
stability,
reduce
high-frequency
vibrations
caused
bubble
shedding.
significantly
advances
understanding
accurately
simulating
revealing
across
different
stages
using
WALE-LES
model.
findings
demonstrate
can
effectively
stabilize
structures
instabilities
overall
performance.
These
insights
will
have
a
impact
design
hydrofoils
development
strategies.
Journal of Fluids Engineering,
Год журнала:
2024,
Номер
147(5)
Опубликована: Окт. 29, 2024
Abstract
Cavitation
erosion
in
hydraulic
machinery
constitutes
a
multifaceted,
instantaneous
physicochemical
process
resulting
material
wear
and
decreased
efficiency.
This
paper
employs
an
enhanced
Eulerian–Lagrangian
method
to
evaluate
cavitation
erosion.
The
captures
erosive
impact
loads
released
by
the
nonspherical
collapse
of
near-wall
bubbles
integrates
them
with
one-dimensional
ductile
mode,
capability
lacking
traditional
homogeneous
mixture
methods.
A
classic
axisymmetric
nozzle
test
case
is
conducted
under
four
different
numbers
(σ
=
0.8,
0.9,
1.09,
1.6)
validate
reliability
new
approach.
Qualitative
quantitative
analysis
demonstrates
that
load
distribution
on
lower
upper
walls
aligns
experimental
measurements.
Compared
reference
works,
accurately
predicts
maximum
position
yields
narrower
area
closer
data.
Moreover,
relative
error
minimum
incubation
time
at
σ
0.9
wall
calculated
4.67%,
rate
36.6%.
pivotal
for
further
studying
how
various
materials
respond
wear.
Further
reveals
response
patterns
are
similar
conditions
1.09.
In
contrast,
surface
reduced
46.7%,
nearly
triples
1.6.
Cavitation-induced
flow
instabilities
in
vortex
pumps
critically
degrade
hydraulic
performance
and
operational
lifespan.
This
study
investigates
the
evolution
of
vapor
cavities
within
across
various
cavitation
states
using
both
numerical
simulations
experimental
analysis.
The
unsteady
dynamics
impeller
channel
are
examined,
relationships
among
pressure
pulsations,
volume,
volume
fraction
analyzed.
As
intensifies,
expands
progressively.
Notably,
time
required
for
to
expand
during
critical
is
twice
as
long
that
severe
cavitation,
whereas
contraction
one-fourth.
variation
inside
follows
a
distinct
pattern,
initially
increasing
then
decreasing,
with
peak
occurring
cavitation.
interactions
between
fraction,
become
increasingly
complex,
especially
where
amplitude
pulsations
significantly
decreases,
increases,
fluctuations
suppressed.
Wavelet
coherence
analysis
reveals
coupling
these
three
variables
different
temporal
scales
frequency
bands,
enhanced
observed
low-frequency
range
(0–50
Hz).
These
findings
provide
valuable
insights
optimization
development
municipal
industrial
fluid
transport
applications.
The
present
work
investigates
the
unequal
splitting
of
cavitation
bubbles
near
rigid
boundaries
within
a
narrow
gap.
Based
on
high-speed
photographic
experiments,
typical
phenomenon
bubble
is
shown,
and
parametric
partitions
in
proximity
to
cylinder
flat
wall
are
presented.
Kelvin
impulse
theory,
underlying
physical
bubble-splitting
mechanisms
explored.
In
addition,
impacts
main
parameters
quantitatively
analyzed.
conclusions
as
follows.
(1)
Under
different
cylinder–bubble
distances,
splits
into
three
cases:
an
upper
larger
part
lower
smaller
part,
two
equal-sized
parts,
part.
(2)
caused
by
inconsistencies
between
directions
bubble-collapse
jet
centroid
movement.
(3)
As
radius
cylinder–wall
distance
increase,
shifts
from
case
1
3,
suggesting
effect
increases
flat-wall
decreases.
