In
this
study,
two-dimensional
flow
around
a
rectangular
cylinder
with
an
aspect
ratio
(AR)
of
5
is
investigated
across
various
attack
angles
(α)
and
Reynolds
numbers
(Re).
A
rise
in
α
improves
RMS
lift
coefficient
CL,
mean
drag
CD
for
the
cylinder,
distinct
turning
points
increase
observed
Re.
Beyond
these
points,
continues
to
rise,
displaying
opposite
trend
Re
increase,
while
maintains
continuous
increase.
Turning
decrease
gradually
increasing
α.
Elevations
both
amplify
coefficients'
magnitude,
volatility,
correlation.
Flow
structure
analysis
reveals
cavity
formation
on
lower
side
trailing
edge
increased
α,
resulting
shear
layer
reattachment.
Mean
velocity
at
rises
higher
Re,
indicating
kinetic
energy
nonlinearity.
High-order
dynamic
mode
decomposition
(HODMD)
method
employed
assess
pressure
fields.
HODMD
shows
that
first
three
modes
dominate
dynamics.
Odd-order
contribute
significantly
lift,
even-order
cancel
each
other.
Increasing
transitions
contribution
from
odd-
even-order.
amplifies
alternation
frequency
vorticity
pressure,
complexity.
Numerical
simulations
are
conducted
to
analyze
flow
characteristics
around
two
tandem
sharp-edged
cylinders
with
cross
sections
of
square
(b1*=1)
for
the
upstream
cylinder
and
rectangle
(b2*)
downstream
(b*=b/a,
where
a
b
sides
cylinder).
This
study
investigates
effects
Reynolds
numbers
(Re
=
30–150),
cross-sectional
aspect
ratios
(b2*=1–4),
scaled
gap-spacing
between
(S*
1–6)
on
structure,
onset
vortex
shedding,
hysteresis,
aerodynamic
parameters
(such
as
drag
coefficient,
Strouhal
number,
root
mean
lift
coefficients,
so
on).
The
results
reveal
that
increasing
b2*
suppresses
shedding
cylinder,
depending
S*.
suppression
is
attributed
interference
effect
adhesion
shear
layers
cylinder.
Three
distinct
time-mean
patterns
identified
based
separation
reattachment
layers.
Flow
pattern
Ι
exhibits
parallel
along
side
faces
while
bubbles
associated
points
formed
in
II
these
faces.
For
III,
no
point
observed,
cover
cylinder'
Additionally,
instantaneous
extended-body
co-shedding
apperceived
within
ranges
examined
Re
behaviors
varying
forces
well
frequency
correlated
structures.
hysteresis
dependence
discussed
comprehensively.
show
critical
decrease
from
127.5
±
2.5
49.5
S*
1
6
(b1*
4).
limit
found
range
3.5≤S*≤4.5
over
4)
at
150.
This
numerical
study
presents
laminar,
two-dimensional
analyses
of
unconfined
flow
over
two
staggered
square
cylinders,
oriented
at
a
45°
angle
relative
to
the
incoming
direction.
The
investigation
examines
six
center-to-center
gap
spacing:
S
=
2D,
3D,
4D,
6D,
8D,
10D,
and
12D,
where
D
indicates
side
length
cylinders.
covers
broad
range
Reynolds
numbers
(Re),
from
1
200,
encompassing
creeping,
steady,
unsteady
regimes.
primary
objective
is
assess
effects
both
Re
S/D
on
patterns
associated
quantities.
Furthermore,
impact
computational
domain
size
results
for
varying
examined.
Another
aim
determine
critical
(Recr)
that
trigger
onset
vortex
shedding.
findings
reveal
as
increases,
Recr
rises,
gradually
approaching
value
with
single
cylinder.
Four
distinct
time-averaged
are
identified
based
streamlines
analysis.
Generally,
downstream
cylinder
exerts
controlling
influence
dynamics
upstream
cylinder,
while
enhances
shedding
counterpart.
comprehensive
aerodynamic
characteristics
attributed
their
contributions
regime
pattern,
degree
merging
occurring
behind
intensity
in
interstitial
space.
However,
significance
becomes
less
pronounced
inter-cylinder
distances
exceeding
due
diminished
mutual
interaction
between
flows
passing
around
The
present
work
employs
the
immersed
boundary
method
to
perform
direct
simulations
of
flow-induced
vibrations
in
a
tandem
cylinder
at
laminar
flows,
where
only
upstream
(UC)
is
allowed
vibrate.
primary
focus
elucidate
vibration
response
UC
and
underlying
hydrodynamic
mechanisms
when
fixed
downstream
(DC)
introduced.
results
indicate
that
varying
spacing
ratios
(L/D)
reduced
velocities
(U*)
leads
both
self-limiting
galloping
lock-in
instabilities
UC.
resonance
regions
for
can
be
categorized
into
different
regimes,
such
as
lock-in,
harmonic
(HLN),
upper
branch,
lower
branch
based
on
various
mechanisms.
Notably,
HLN
regime
are
distinct
from
traditional
observed
bare
cylinder,
with
oscillation
frequency
locking
onto
higher-order
fluid
force
occurrence
larger
amplitudes.
Regarding
interference
instability,
we
show
amplitude
related
vortex
shedding
points
either
side
DC.
introduction
DC
observation
six
modes:
C(2S),
2S,
P+T,
2T,
2P,
Aperiodic.
Among
these,
weak
vortices
2P
mode
found
suppress
amplitude.
asymmetrical
aperiodic
evolution
wake
flow
generates
even-order
forces.
Furthermore,
an
analysis
energy
transfer
indicates
cylinders
exhibit
high
kinetic
conversion
ability
over
wide
range
U*−L/D.
This
study
conducts
two-dimensional
numerical
simulations
of
the
flow
over
four
square
cylinders
arranged
side
by
at
a
low
Reynolds
number
(Re)
100.
The
investigation
primarily
centers
on
influence
gap
to
cylinder
width
ratio
(g*)
flow.
range
g*
spans
from
0.1
7.0.
Within
this
parameter
range,
three
distinct
regimes
emerge
based
inherent
characteristics.
These
are
defined
as
follows:
(1)
single
bluff
body
(g*
≤
0.3),
(2)
flip-flopping
(0.3
<
2.0),
and
(3)
modulated
periodic
≥
2.0).
Additionally,
is
further
categorized
into
patterns.
Various
aspects
these
different
examined,
including
vortex
contours,
velocity
fields,
liquid
force
coefficients
around
cylinders.
Moreover,
detailed
illustrations
provided
for
modulation
behaviors
in
structures
coefficients.
Finally,
proper
orthogonal
decomposition
technique
employed
identify
analyze
underlying
spatial
coherent
field,
offering
insights
dynamic
features
wakes.
Physics of Fluids,
Год журнала:
2024,
Номер
36(11)
Опубликована: Ноя. 1, 2024
The
flow
structure
and
reattaching
characteristic
of
two
tandem
rectangular
cylinders
with
aspect
ratio
being
5:1
have
been
investigated
through
wind
tunnel
experiments
three-dimensional
large
eddy
simulation
(LES)
methods.
gap
width
G
between
the
varies
from
2
times
D
to
20
D,
where
represents
depth
cylinders.
surface
pressure
distribution
aerodynamic
forces
each
cylinder
are
obtained
via
experiments.
Two
distinct
patterns
identified
increasing
LES
methods,
results
presented
in
good
agreement
as
well.
experimental
numerical
indicate
that
is
highly
sensitive
variation
G,
leading
alterations
aerodynamics
vortex-shedding
Furthermore,
also
capture
shift
points
increases.
Additionally,
following
findings,
a
proposed
criterion
based
on
data
for
predicting
boundary
layer
reattachment
Journal of Marine Science and Engineering,
Год журнала:
2024,
Номер
12(9), С. 1547 - 1547
Опубликована: Сен. 4, 2024
In
the
field
of
ocean
engineering,
variation
flow
during
ship-to-ship
(STS)
interaction
has
been
a
hot
topic.
Noteworthy,
effect
vortex
distribution
on
characteristic
variations
STS
remains
insufficiently
researched.
This
study
modifies
RNG
k-ε
model
using
OpenFOAM
platform
and
verifies
its
reliability
by
comparing
it
with
literature
data.
Subsequently,
extended
research
is
conducted
to
investigate
characteristics
two
different
ship
hull
sections
under
Reynolds
numbers
(Re=68,000
Re=6800),
analyzing
velocity
components,
distribution,
trends
in
pressure
turbulent
kinetic
energy
fields
relative
field.
The
reveals
that
Re
primarily
governs
changes
upstream
downstream
fields,
while
gap
field,
more
constrained
geometry
boundary
conditions.
provides
valuable
reference
for
assessing
interactions.
