arXiv (Cornell University),
Journal Year:
2021,
Volume and Issue:
unknown
Published: Jan. 1, 2021
Traditional
Cauchy-Stokes
decomposition
of
velocity
gradient
tensor
gives
a
symmetric
and
an
anti-symmetric
subtensors
which
are
called
the
strain-rate
vorticity
tensors.
There
two
problems
with
decomposition.
The
first
one
is
that
or
cannot
represent
fluid
rotation
vortex.
second
(strain-rate)
distinguish
stretching
(compression)
shear.
shear
dependent
on
coordinate
not
Galilean
invariant.
Since
between
non-rotational
rigid
rotation,
has
been
decomposed
to
Liutex
in
our
previous
work.
A
Liutex-based
principal
was
developed
as
(Liutex
tensor),
pure
tensor,
However,
made
at
each
point
own
different
from
other
points.
This
paper
derives
original
xyz
system,
and,
therefore,
provides
new
tool
for
kinematics
conduct
shear,
invariant
clear
physical
meanings.
could
become
foundation
kinematics.
Engineering Applications of Computational Fluid Mechanics,
Journal Year:
2021,
Volume and Issue:
15(1), P. 1613 - 1628
Published: Jan. 1, 2021
The
dominant
vortex
structure
near
the
hub
in
rotor
corner
separation
flow
has
an
important
influence
on
internal
of
axial
rotating
machinery.
However,
current
quantitative
research
key
vortical
characteristics
is
still
insufficient.
analysis
(horn-like
vortex)
pump
was
conducted
and
found
that
average
intensity
turbulence
eddy
dissipation
show
a
gradual
weakening
trend
along
core
line
from
region
to
tail
under
various
working
conditions.
evolution
horn-like
life
cycle
includes
five
stages,
inception-growth-development-attachment-decay
typical
condition
0.62Q0.
statistical
frequency
periodic
about
2.76
times
shaft
rotation
frequency.
pressure
fluctuation
induced
by
increases
rapidly
dominates
channel.
peak-peak
value
impeller
outlet
section
close
2.79
inlet
should
be
paid
enough
attention
to.
Engineering Applications of Computational Fluid Mechanics,
Journal Year:
2021,
Volume and Issue:
15(1), P. 1016 - 1033
Published: Jan. 1, 2021
Vortex
is
the
dominant
flow
structure
in
hydro-energy
machinery,
and
its
swirling
features
are
mainly
determined
by
rigid
rotation
part
of
vorticity.
In
this
study,
vorticity
transport
equation
proposed
based
on
decomposition.
The
vortex
spatial
evolution
described
stretching
term
RST,
dilatation
RDT,
Lamb
RCT
viscous
RVT.
shape
change
a
tube
affected
RST
while
production
dissipation
reflected
Compared
with
traditional
equation,
new
theoretical
tool
can
distinguish
between
shearing
motion
local
fluids,
it
better
reveal
intuitive
characteristics
vortical
structures.
Two
cases
clear
engineering
demands
analysed
using
results
show
that
provide
practical
method
for
analysis
control
flows
machinery.
Physics of Fluids,
Journal Year:
2023,
Volume and Issue:
35(5)
Published: May 1, 2023
Hydraulic
consistency
between
a
prototype
pump
and
its
hydraulic
model
is
generally
considered
to
be
satisfied,
that
is,
the
energy
performance
flow
structures
conform
similarity
law.
However,
such
may
not
always
exist
in
actual
engineering
projects.
Head
change
vibration
enhancement
large-scale
bulb
tubular
pumps
are
exhibited,
but
reason
for
this
inconsistency
still
unclear.
In
article,
case
study
was
performed
South-to-North
Water
Diversion
Project
China,
pressure
characteristics
impeller
were
explored
under
optimal
condition.
An
interesting
new
phenomenon,
polarization
oscillation,
found.
Its
most
important
feature
constant
difference
average
values
among
axisymmetric
blades,
blades
with
exhibit
large-amplitude
oscillations
around
different
values,
one
revolution
equivalent
rotating
cycle
due
failure
of
consistency.
Further
in-depth
analysis
reveals
realized
by
adjustment
resultant
force
Coriolis
potential
rothalpy
gradient
fluid
motions
sinusoidal
disturbance
gravity,
action
path
presents
hysteresis
loop
rotating.
This
mode
leads
special
conversion
gravity
energy,
kinetic
and,
thus,
hydrostatic
at
initial
phase
cannot
fully
eliminated;
transition
sides
along
against
inconsistent.
finding
suggests
induced
should
if
conventional
applied
pumps.
Physics of Fluids,
Journal Year:
2024,
Volume and Issue:
36(7)
Published: July 1, 2024
Separation
flows
tend
to
induce
a
chaotic
flow
field
that
eventually
leads
energy
losses
and
reduced
efficiency.
The
present
study
performed
multiobjective
optimization
improve
the
hydraulic
performance
of
an
axial
pump
at
best
efficiency
point
(BEP)
critical
stall
based
on
diffuser
vane
(DV)
geometry.
Computational
fluid
dynamics
were
applied
predict
series
DV
models
with
design
points
generated
through
experiment.
Six
different
surrogate
evaluated
R-squared
criteria.
nondominated
sorting
genetic
algorithm
II
was
also
employed
search
for
optimum
solutions
variables.
Hydraulic
balance
between
low
high
rate
conditions
analyzed
velocity
triangle.
After
optimization,
total
head
BEP
model
increased
by
2.341%
2.779%,
respectively,
compared
reference
model.
Despite
minimal
changes
point,
optimal
operating
range
notably
expanded
in
region.
Thorough
evaluation
attributed
horseshoe,
corner,
trailing-edge
vortices
conducted
meridional
planes,
multiple
spans,
various
cross
sections
domain.
Additionally,
formation
development
turbulent
detail
transient
simulation.
Vibration
noise
caused
instabilities
characteristics
substantially
36.76%
67.342%
first
higher-harmonic
frequencies
respectively.
Journal of Fluids Engineering,
Journal Year:
2022,
Volume and Issue:
144(9)
Published: March 17, 2022
Abstract
The
blade
slip
factor
significantly
influences
the
prediction
accuracy
of
self-closure
one-dimensional
flow
model
for
side
chambers
centrifugal
pumps.
Wiesner's
and
Stodola's
factors,
which
are
used
to
formulate
outlet
pressure
served
as
boundary
condition
model,
examined,
is
an
improvement
previous
study
(Gu
et
al.,
2020,
“A
Pressure
Model
Open
Rotor–Stator
Cavities:
An
Application
Adjustable-Speed
Centrifugal
Pump
With
Experimental
Validation,”
ASME
J.
Fluids
Eng.,
142(10),
p.
101301).
Both
computational
fluid
dynamics
(CFD)
simulations
experiments
pump
conducted
support
improvement.
A
good
agreement
exists
between
performance
at
best
efficiency
points
(BEPs)
different
rotating
speeds
obtained
by
experiments.
Through
CFD
analysis,
in
impeller
remarkably
deviates
from
blade-congruent
flow,
especially
quasi-triangular
regions
downstream
throats.
Meanwhile,
reason
over-predictions
chamber
that
embeds
(FMW)
expression
underestimates
deflection
overestimates
boundary.
By
contrast,
with
(FMS)
closer
terms
relative
angle
inlet
pressure.
Compared
measurements,
FMS
upgraded
approximately
3.5%
than
FMW.
At
BEPs
speeds,
generates
lower
shroud
thrust
coefficients
but
slightly
greater
volumetric
efficiencies
This
work
provides
a
simple
approach
better
calculate
characteristics
chambers.
