A
large
amount
of
vegetation
in
nature
exists
the
form
heterogeneous
patches,
and
variations
characteristics
significantly
affect
water
flow
structures.
The
objective
this
study
is
to
investigate
effect
alternating
sparse
dense
patches
on
turbulence
characteristics.
Multiple
sets
scenarios
were
designed
for
numerical
simulation
analysis,
a
comparison
was
made
with
homogeneous
vegetation.
Results
indicate
that
compared
vegetation,
arrangement
alters
distribution
velocities
zone
main
channel,
promoting
material
exchange
between
these
regions.
density
difference
channel
increases
larger
differences,
but
magnitude
limited
generally
remains
within
10%
width.
In
balance
equation
turbulent
kinetic
energy,
terms
are
influenced
differently
by
changes
density.
As
increases,
convective
term
gradually
while
production
diffusion
exhibit
“lower
middle,
higher
at
both
ends”
pattern.
dissipation
demonstrates
reduction
low-density
ultimately
exhibits
an
amplification
effect.
Furthermore,
determines
using
data
from
mid-height
represent
entire
cross
section
may
result
maximum
error
up
11%.
Water,
Год журнала:
2023,
Номер
15(1), С. 176 - 176
Опубликована: Янв. 1, 2023
Aquatic
vegetation
appears
very
often
in
rivers
and
floodplains,
which
significantly
affects
the
flow
structure.
In
this
study,
experiments
have
been
conducted
to
investigate
effects
of
submerged
arrangement
patterns
density
on
Deflected
non-bending
is
arranged
square
staggered
configurations
channel
bed
a
large-scale
flume.
Results
showed
that
configuration
leads
intensified
streamwise
velocity,
turbulence
kinetic
energy
(TKE),
Reynolds
shear
stress
(RSS)
compared
configuration.
When
low
(λ
=
0.04
λ
0.07),
produced
wake
rear
more
expansive
than
with
high
0.09
0.17)
because
velocity
center
four
elements
lower
middle
two
density.
TKE
zone
deflected
indicate
maximum
root-mean-square
fluctuations
occur
at
sheath
section
(z/H
0.1)
top
0.4).
behind
elements,
value
RSS
occurred
slightly
above
interface
between
non-vegetation
layer,
showing
Kelvin–Helmholtz
instability
associated
inflectional
points
longitudinal
velocity.
Within
range
study
(0.04
<
≈<
0.23),
as
increases,
negative
positive
values
throughout
depth
increase.
Environmental Fluid Mechanics,
Год журнала:
2023,
Номер
23(1), С. 125 - 140
Опубликована: Янв. 11, 2023
Abstract
Bridge
pier
is
a
common
feature
in
hydraulic
structure.
Its
impact
to
the
river
usually
occurs
group
form
rather
than
single
pier,
so
this
challenging
piers-group
influence
towards
hydraulics
and
turbulence
needs
be
explored.
In
paper,
measurements
were
conducted
using
an
Acoustic
doppler
velocimeter
(ADV)
study
velocities
three
dimensions
(longitudinal,
transversal,
vertical).
Based
on
experimental
data,
we
have
observed
reversed
depth-averaged
velocity
vector
after
each
of
three-pier.
The
analysis
has
been
contribution
bursting
event
Reynolds
shear
stress
(RSS)
generation,
order
identify
critical
events
structures
around
piers.
upstream
near-wake
flow
bed-wall
layer,
strong
sweep
ejection
observed;
while
at
downstream,
sweeps
more
dominant.
pattern
burst
changed
outer
layer
flow,
where
ejections
Furthermore,
fractional
ratio
RSS
variation
hole
size
H
=
0
indicates
that
significantly
generated
near
wake-flow
upstream.
There
is
an
urgent
need
to
predict
the
bed-load
transport
rate
in
vegetated
river
ecosystems
support
restoration
efforts.
In
response,
we
have
developed
a
novel
model
for
estimating
effective
shear
stress
acting
on
riverbed.
This
based
energy
equation
and
considers
intrinsic
relationship
between
loss
mean
flow
turbulence
generated
by
vegetation
open
channel
flows
with
emergent
vegetation.
Using
this
bed
model,
assessed
performance
of
Meyer-Peter–Müller
(MPM)
formula
predicting
comparing
it
collected
literature
experimental
data.
The
results
revealed
that
MPM
does
not
provide
accurate
predictions.
It
tends
overestimate
when
dimensionless
approximately
less
than
one
underestimate
them
greater
one.
suggests
enhances
decreases
sediment
larger
or
lower
one,
respectively.
Consequently,
modified
coefficients
using
extensive
data,
leading
development
predictive
flows.
new
outperforms
existing
equations
bedload
rate,
even
umbrella-like
Water Resources Research,
Год журнала:
2024,
Номер
60(5)
Опубликована: Май 1, 2024
Abstract
Widely
distributed
in
natural
rivers
and
coasts,
vegetation
interacts
with
fluid
flows
sediments
a
variable
complicated
manner.
Such
interactions
make
it
difficult
to
predict
associated
drag
forces
during
sediment
transport.
This
paper
investigates
the
coefficient
for
an
emergent
vegetated
patch
area
under
nonuniform
flow
mobile
bed
conditions,
based
on
analytical
model
solving
momentum
equation
following
our
previous
work
(Zhang
et
al.,
2020,
https://doi.org/10.1029/2020WR027613
).
Emergent
was
modeled
rigid
cylinders
arranged
staggered
arrays
of
different
coverage
∅.
Laboratory
flume
tests
were
conducted
measure
variations
both
water
surfaces
along
sand
bed.
Based
experimental
theoretical
analyses,
dimensionless
integrating
terms
properties
effects
is
proposed
C
d
over
The
calculated
values
exhibit
two
trends,
that
is,
nonmonotonically
or
monotonically
increasing
streamwise
direction,
due
combined
effect
surface
gradient
slope.
morphodynamic
response
manifests
as
evolution
slope
within
patch.
Ongoing
scouring
directs
flow's
energy
toward
overcoming
rising
slope,
leading
relatively
stable
stage
low
transport
rate.
study
advances
existing
understanding
coefficient's
role
flows.
It
also
enhances
applicability
models
riverine
restoration.
Journal of Hydrology,
Год журнала:
2024,
Номер
636, С. 131280 - 131280
Опубликована: Май 3, 2024
A
common
feature
of
cold
regions
is
the
presence
ice
cover
on
water
surface.
IN
vegetation
in
channel
bed
which
normally
leafless
winter,
interaction
between
river
and
vegetated
becomes
very
complex.
In
present
study,
impacts
submerged
deformation
flow
resistance
have
been
investigated
based
144
experiments
conducted
a
large-scale
outdoor
flume.
The
independent
variables
associated
with
maximum
scour
depth
around
elements
assessed
equations
developed.
Results
indicate
that
most
important
variable
affecting
under
ice-covered
conditions
ratio
roughness
to
(ni/nb).
However,
open
conditions,
Froude
number
influencing
depth.
methods
law
wall
provide
reliable
Manning's
coefficient
for
both
smooth
rough
covers
bed.
As
density
increases,
size
holes
smaller.
With
increase
density,
median
grain
armour
layer
decreases
correspondingly.
When
are
placed
staggered
configuration,
less
than
squared
configuration
elements.
Regardless
surface
sediment
bed,
always
occurs
at
upstream
front
face
each
element.
Under
condition,
more
conditions.
