Transactions of the JSME (in Japanese),
Год журнала:
2024,
Номер
90(933), С. 23 - 00257
Опубликована: Янв. 1, 2024
In
order
to
improve
a
vibrational
power
generator
using
magnetostrictive
material,
i.e.,
Iron-gallium
alloy,
and
flow-induced
vibration
of
cantilevered
cylinder,
fixed
splitter
plate
was
installed
behind
circular
cylinder.
Effects
gap
between
cylinder
on
the
performance
response
amplitude,
vortex
shedding
frequency
were
investigated
through
wind
tunnel
experiments.
Flow
visualizations
around
also
conducted
by
smoke-wire
method
high-speed
camera.
The
test
models
had
span
length
L
200
mm,
300
mm
400
mm.
diameter
D
40
A
with
thickness
2
center
model
G
varied
from
8
104
For
small
ratio
G/D
≤
0.6,
galloping
occurred.
From
smoke
wire
visualization,
it
related
that
upstream
flow
went
along
side
surface
inner
circulatory
generated
near
gap.
As
result,
accelerated
gap-flow
occurred
negative
pressure
periodically
upper
or
lower
wall
large
≥
1.2,
did
not
occur,
amplitude
became
similar
without
plate.
generation
having
=
0.2
largest.
However,
onset
velocity
larger
than
other
cylinders
gaps.
This
paper
numerically
investigated
the
vortex-induced
vibration
of
two
rigidly
connected
tandem
cylinders
with
streamwise
spacing
ranging
from
1.5D
to
4.5D.
The
identical
possess
a
mass
ratio
2
and
damping
0.001.
Simulations
are
conducted
at
low
Reynolds
number
100
over
reduced
velocity
range
2–18.
Five
wake
interference
modes
identified
in
terms
evolution
vortex
shedding
shear
layers
different
Ur
L/D,
including
overshoot
mode,
continuous
reattachment
alternate
(AR)
quasi-co-shedding
(QCS)
co-shedding
(CS)
mode.
Furthermore,
AR
mode
can
be
divided
into
merging
(ARM)
(ARS)
on
basis
whether
shed
upstream
cylinder
merges
downstream
cylinder.
transition
two-layered
vortices
secondary
street
is
observed
when
L/D
=
3.5
5,
4.5
5–8,
where
experience
larger
cross-flow
amplitudes
occurrence
QCS
or
CS
Journal of Marine Science and Engineering,
Год журнала:
2025,
Номер
13(5), С. 971 - 971
Опубликована: Май 16, 2025
To
investigate
the
suppression
method
for
vortex-induced
vibrations
(VIV)
of
two-degree-of-freedom
(2-DOF)
rotating
cylinders
with
dual
splitter
plates,
numerical
simulations
are
conducted
at
a
Reynolds
number
200,
mass
ratio
2.6,
and
rotation
2.
The
effects
gap
distance
width
plates
on
vibration
response,
hydrodynamic
coefficients,
flow
wakes
examined.
results
show
existence
distinct
mechanisms
between
low
distances
(G/D
=
0.25–0.5)
high
0.75–2.0).
Furthermore,
(W/D)
is
considered
as
critical
factor
in
effectiveness.
distributions
wake
patterns
under
different
analyzed,
six
observed.
Finally,
lift
drag
coefficients
examined,
revealing
their
sensitivities
to
G/D
W/D.
optimal
parameters
determined.
Marine
drilling
persistently
subjected
VIV,
which
critically
compromise
structural
stability.
findings
this
study
deliver
engineering
value
marine
riser
VIV
suppression.
Physics of Fluids,
Год журнала:
2024,
Номер
36(11)
Опубликована: Ноя. 1, 2024
Piezoelectric
energy
harvesting
from
ambient
vibrations
offers
a
promising
small-scale
generation
strategy,
with
wake-induced
vibration
of
flexible
structures
being
an
ideal
candidate.
This
study
examines
bluff
body
followed
by
fully
piezoelectric
flapper
in
viscous
free-stream
flow
using
in-house
discrete
forcing
immersed
boundary
method-based
fluid-structure-electric
solver
for
parametric
investigation.
Different
vortex
shedding
regimes
are
identified
based
on
formation
around
the
flapper.
The
complex
and
interdependent
spatiotemporal
dynamics
wake
dictated
parameters
such
as
bending
rigidity
gap
space
between
result
various
deformation
profiles,
influencing
strain
rate
output
power.
also
investigates
independent
variation
length
its
impact
vortical
arrangements
flexibility,
introducing
different
oscillation
modes.
present
takes
nuanced
view
overall
their
mutual
effect
power
output,
unlike
most
existing
studies
where
enhancing
amplitude
frequency
oscillations
optimal
was
main
concern.
Factors
curvature,
asymmetry,
periodicity
have
been
especially
highlighted
context
corresponding
spaces
investigated.
Interestingly,
increase
piezo-flapper
has
seen
reduction
though
it
instrumental
bringing
symmetry
back.
comprehensive
insights
into
underlying
dynamical
mechanisms
can
contribute
toward
design
future
devices.
Physics of Fluids,
Год журнала:
2023,
Номер
35(12)
Опубликована: Дек. 1, 2023
This
paper
reported
the
numerical
results
of
flow
past
a
flexible
splitter
plate
attached
to
rear
rigid
circular
cylinder
at
low
Reynolds
number
160.
The
finite-volume
method
(FVM)
in
OpenFOAM-9
and
finite-element
(FEM)
deal.ii
are
utilized
solve
fluid
solid
domains
fluid–structure
interaction
(FSI)
issue,
respectively.
effects
length
L/D
normalized
Young's
modulus
E*
examined.
According
equilibrium
position
bending
deformation
order,
five
response
modes
identified,
including
symmetry-I,
symmetry-II,
symmetry-III,
bifurcation-I,
bifurcation-II.
amplitude
plate-tip
is
enhanced
as
vortex
shedding
frequency
approaches
natural
frequency.
Nevertheless,
bifurcation
observed
between
symmetry-I
symmetry-II
modes,
where
vibration
sharply
drops.
local
vortices
occurring
along
surface
increases
with
length,
leading
more
negative
pressure
regions.
Consequently,
higher
mode
excited.
greater
shear
stress
occurs
small
curvature
radius
during
deformation.
2S
(a
pair
alternately
shed
per
cycle)
recognized
most
cases.
In
contrast,
P
+
S
from
one
side
single
other
side)
bifurcation-II
relatively
large
amplitude.
Due
deflection,
wake
becomes
asymmetrical
significant
elongation
recirculation
region.
Four
behaviors
boundary
layers
identified.
reduction
hydrodynamic
forces
achieved
when
experiences
bifurcation.
Vibration
and
rotation
represent
two
common
fluid–structure-interaction
phenomena,
which
can
occur
independently
or
concurrently.
While
extensive
research
has
been
conducted
on
individual
vibration/rotation
cases,
there
is
relatively
limited
literature
coupled
cases.
However,
it
crucial
to
recognize
that
responses,
such
as
those
observed
in
falling
leaves,
are
more
prevalent
both
natural
occurrences
engineering
scenarios.
Hence,
this
study
aims
investigate
the
influence
of
cross-flow
vibrations
flow-induced
rotations
an
elastically
mounted
cylinder-plate
system.
A
broad
range
rotational
reduced
velocities,
spanning
Uθ
=
2–18,
examined
across
four
distinct
vibrational
namely
Uy
5,
8,
12,
18.
Numerical
results
indicated
a
bifurcation
phenomenon,
wherein
deflects
non-zero
equilibrium
position,
occurs
at
high
values
Uy.
Four
response
modes
have
identified:
vibration-dominated,
rotation-dominated,
augmentation
(VIV-like),
(galloping-like)
mode.
These
exert
significant
phase
angles
between
rotary
angle
displacement
well
vortex
shedding
modes.
In
rotation-dominated
region,
VIV-like
galloping-like
exhibit
continuous
decreasing
trend,
consistent
level
180°
90°,
respectively.
Transitions
vibration
responses
result
sharp
increases
angles.
The
wake
flow
mode
demonstrates
2S
(two
single
vortices),
while
vibration-dominated
characterized
by
predominant
2T
triplets
vortices).
large
amplitudes
lead
increase
numbers
vortices,
presenting
2S,
2S*,
2P
pairs
vortices)
2P,
P
+
S
(one
pair
one
2P+S
where
2S*
consists
each
exhibiting
tendency
split
into
smaller
vortices
they
migrate
downward.
mechanism
behind
notable
amplification
rotation/vibration
elucidated.
Apart
from
pressure
difference
induced
shedding,
additional
driving
force
resulting
relative
motion
transverse
direction
contributes
total
torsional
force,
thereby
leading
responses.
Furthermore,
streamlined
profile
accounts
for
escalation
amplitudes.
To
explore
suppression
method
on
vortex-induced
vibrations
(VIVs)
response
of
the
rotating
cylinders,
VIVs
two-degree-of-freedom
cylinders
with
dual
splitter
plates
at
a
Reynolds
number
200
and
mass
ratio
2.6
are
investigated
via
numerical
simulations.
The
results
show
that
more
effective
suppressing
VIV
in
low
rotation
rates,
effect
decreases
increasing
rate.
Three
flow
patterns
defined
[overshoot,
merge
shedding,
individual
shedding],
distributions
wake
under
different
rates
gap
distances
discussed.
vibration–fluid
force–wake
interaction
is
analyzed,
variation
accompanied
by
sudden
increase
amplitude
fluid
force.
In
addition,
directional
sensitivity
lift
drag
discussed,
sensitive
to
rate,
distance.
