Generalised Jeffery's equations for rapidly spinning particles. Part 1. Spheroids
Journal of Fluid Mechanics,
Journal Year:
2024,
Volume and Issue:
979
Published: Jan. 9, 2024
The
observed
behaviour
of
passive
objects
in
simple
flows
can
be
surprisingly
intricate,
and
is
complicated
further
by
object
activity.
Inspired
the
motility
bacterial
swimmers,
this
two-part
study
we
examine
three-dimensional
motion
rigid
active
particles
shear
Stokes
flow,
focusing
on
bodies
that
induce
rapid
rotation
as
part
their
In
Part
1
develop
a
multiscale
framework
to
investigate
these
emergent
dynamics
apply
it
spheroidal
objects.
2
(Dalwadi
et
al.
,
J.
Fluid
Mech.
vol.
979,
2024,
A2)
our
understand
more
complex
shapes;
helicoidal
with
chirality.
Via
multiple
scales
asymptotic
analysis
for
nonlinear
systems,
systematically
derive
equations
long-term
trajectories
explicitly
account
strong
(leading-order)
effects
fast
spinning.
Supported
numerical
examples,
constructively
link
effective
well-known
Jeffery's
orbits
spheroids,
deriving
an
explicit
closed-form
expression
shape
particle,
broadening
scope
seminal
spinning
spheroids.
Language: Английский
Buoyancy–flow coupled dispersion of active spheroids in a vertical pipe: effects of elongation and settling
Journal of Fluid Mechanics,
Journal Year:
2025,
Volume and Issue:
1007
Published: March 24, 2025
Many
particles,
whether
passive
or
active,
possess
elongated
shapes.
When
these
particles
settle
swim
in
shear
flows,
they
often
form
regions
of
accumulation
and
depletion.
Additionally,
the
density
contrast
between
fluid
can
further
alter
flow
by
increasing
local
suspension
density,
resulting
a
two-way
buoyancy–flow
coupling
mechanism.
This
study
investigates
coupled
dispersion
active
spheroids,
examining
effects
elongation,
orientation-dependent
settling
gyrotaxis
vertical
pipe
subjected
to
either
downwards
upwards
discharge.
While
concentration
velocity
profiles
spheroids
spherical
gyrotactic
swimmers
be
analysed
similarly
recent
study,
notable
differences
characteristics
emerge
due
different
streamline-crossing
mechanisms.
For
suspensions
swimmers,
interplay
settling,
gyrotaxis-induced
shear-induced
trapping
results
distinct
distributions
compared
those
neutrally
buoyant
extremely
dilute
with
negligible
effect.
These
impact
drift
velocity,
dispersivity,
time
elapsed
steady
under
varying
rates.
Interestingly,
low-shear
non-settling
around
centreline,
commonly
observed
planar
Poiseuille
flow,
is
absent
change
confinement
from
reflectional
rotational
symmetry.
However,
show
non-trivial
response
strong
downwelling
phenomenon,
linked
centreline
bears
similarities
flow.
Language: Английский
Rapidly yawing spheroids in viscous shear flow: emergent loss of symmetry
Journal of Fluid Mechanics,
Journal Year:
2025,
Volume and Issue:
1009
Published: April 15, 2025
We
investigate
the
emergent
three-dimensional
(3-D)
dynamics
of
a
rapidly
yawing
spheroidal
swimmer
interacting
with
viscous
shear
flow.
show
that
rapid
generates
non-axisymmetric
effects,
active
behaving
as
an
effective
passive
particle
two
orthogonal
planes
symmetry.
also
demonstrate
this
asymmetry
generated
by
can
cause
chaotic
behaviour
in
dynamics,
stark
contrast
to
rotating
spheroids,
which
are
equivalent
those
spheroids.
In
general,
we
find
shape
under
is
different
average
particle.
Moreover,
despite
having
symmetry,
not
ellipsoid
except
for
specific
scenarios
spheroid.
these
scenarios,
calculate
analytically
aspect
ratio
use
multiple
scales
analysis
systems
derive
behaviour,
requires
solving
non-autonomous
nonlinear
3-D
dynamical
system,
and
validate
our
via
comparison
numerical
simulations.
Language: Английский
Sedimentation dynamics of triply twisted Möbius bands: Geometry versus topology
Physical Review Research,
Journal Year:
2024,
Volume and Issue:
6(3)
Published: Aug. 6, 2024
We
explore
the
sedimentation
dynamics
of
triply
twisted
Möbius
bands,
each
characterized
by
threefold
rotational
symmetry
but
distinguished
its
construction
and
intrinsic
geometrical
properties.
Three
types
bands
are
considered:
one
with
vanishing
Gaussian
curvature,
constructed
isometrically
deforming
flat
rectangular
strips
through
bending
without
stretching;
two
negative
being
helicoids.
Experiment
on
these
three
a
focus
varying
aspect
ratios,
reveals
singular
phenomenon:
while
spin
directions
not
derived
from
helicoids
in
consistent
their
inherent
chirality,
exhibit
an
aspect-ratio-dependent
spin,
pointing
to
existence
critical
ratio
at
which
geometric
factors
dominate
over
chiral
influences.
Supported
numerical
simulations
detailed
analysis
resistance
tensors,
we
propose
unique
response
originates
complex
interaction
among
geometry,
topology,
hydrodynamics.
Two
explanations
offered
for
transition
observed
helicoid.
First,
this
may
parallel
superhelices,
competing
chiralities
influence
behavior.
Second,
properties
helicoids,
coupled
deviations
between
rotation
axis
local
axis,
underlie
transition.
Our
study
underscores
significant
role
topological
nuances
determining
behavior
objects
suspended
fluids.
In
addition
offering
transformative
potential
across
diverse
fields,
it
promises
advancements
mixing,
separation
processes,
innovative
passive
swimmers.
Published
American
Physical
Society
2024
Language: Английский