Homepage Ko van der Weele
Research Themes
Granular
Dynamics
> Clustering
cars, beads, and birds
(a) "Cluster's last stand":
Collapse of a granular
cluster
(b) Clustering cars: traffic
jam formation
(c) Competitive clustering: David vs. Goliath
(d) Birds of a
feather. . . : flocking as a phase transition (paper 87)
> Complex Matter Project
> "Bouncing
beads outwit Feynman": Granular realization of a Brownian motor (paper 79)
> Inverse Chladni
patterning: New surprises in a classic demonstration experiment
> Faraday heaping: The self-assembling
interplay of air & sand
> Granular Leidenfrost
effect & beyond: The collective dynamics of "boiling particles"
>
Meteor impact on a laboratory scale: Dinosaurs beware!
>
Granular
roll waves on a chute: How
many will survive in the end? (paper 89)
Fluid
Dynamics
> Physics of the
Granite Sphere Fountain (paper 88)
> Solitary water waves:
Exploring the limits of the KdV soliton
> Leaping Shampoo (3-minute movie,
31 MB)
Winning
entry in the Gallery of Fluid Motion
at the 59th Annual Meeting of the
Division of
Fluid Dynamics of the APS,
November 24-26, 2006, in Tampa Bay,
Florida.
See also publications 62,
63, 66.
Picture by Michel Versluis,
Univ. of Twente, The Netherlands.
Free Field
Physics: questions inspired by phenomena from daily life
>> How on earth can a solid
granite sphere be levitated by a thin film of water?! (paper
88)
>> In the relativistic paradox of the
barn and the pole, is the pole caught after all? Or not? (paper
64)
>> When a
horse accelerates, why does it first walk,
then trot and finally break into a gallop? (paper 33)
>> Throw a ball straight up in the air. What do you
think: does the way down take just as long as the way up? (paper
27)
>> How
efficiently do you chew? A mathematical description of the grinding of food
particles (paper 6)
Nonlinear
Dynamics
> The Route to Chaos via
period-doubling bifurcations:
(a) in 1D
maps with a maximum of order z > 1, yielding (among other things) the Feigenbaum numbers δ(z) and α(z) and an
analytical relation between them! (publications 3, 4, 7)
(b) in
anti-symmetric maps, where the sequence of period doublings is enriched by an
intermediate symmetry-breaking bifurcation (publication 20)
(c) in 2D
maps with a Jacobian between 1 and 0, showing the
not-too-smooth crossover from conservative (Hamiltonian) to purely dissipative
behavior (publications
1, 2, 5, 7)
> The Route to Chaos via
intermittency:
(a)
including a proof that the length of the intermittent phase in 1D maps cannot
be arbitrarily short (papers 10, 11, 13, 15)
(b) and a
scaling law for the width of the periodic windows as function of their period (paper 14)
> Resonances and bifurcations
in 2D maps
(a) The
1:3 resonance (and the associated loss of stability via the "squeeze
effect") in area-preserving maps (publications 7, 8, 9)
(b) The
birth of twin periodic orbits (Poincare-Birkhoff
chains) in non-twist maps (publications 7, 9, 12, 18)
(c) On the
occurrence of "Rimmer type" saddle-node
bifurcations (and the associated birth of repellors
and attractors) in maps with time-reversal symmetry (paper 17)
Coupled
Nonlinear Oscillators
> The complex dynamics of two
coupled, parametrically driven pendulums (papers 23,
25, 26, 27, 28)
(a)
Generalization to 4 parametrically driven pendulums: the locomotion of
four-legged animals (papers 30, 33, 34)
(b) Reduction
to 1 parametrically driven pendulum: resonances, routes to chaos & the
stable dance of the inverted pendulum (papers 16, 19, 20)
> The spring
pendulum: a fascinating example of two coupled oscillators (paper 24)
> Discrete
breathers (localized oscillatory modes) in an array of coupled nonlinear oscillators:
unfolding the homoclinic tangle (papers 31,
32)
Homepage Ko van der Weele