Granular mixing in 2 and 3 dimensions
Rob Sturman
Department of MathematicsUniversity of Leeds
Dynamical Systems Seminar, 19 October 2007Surrey
Joint work with Steve Meier, Julio Ottino, NorthwesternSteve Wiggins, University of Bristol
Rob Sturman Granular mixing
Mixing
Mixing of granular materials:is important — Science 125th anniversary identifiedgranular flow as one of the 125 big questions in Scienceis ubiquitous — pharmaceuticals, food industry, ceramics,metallurgy, constructionwas initially explained by analogies with fluid mixing —hence terms like granular shear and granular diffusion
But the big difference is that granular materials tend tosegregate
Rob Sturman Granular mixing
Mixing
Mixing of granular materials:is important — Science 125th anniversary identifiedgranular flow as one of the 125 big questions in Scienceis ubiquitous — pharmaceuticals, food industry, ceramics,metallurgy, constructionwas initially explained by analogies with fluid mixing —hence terms like granular shear and granular diffusion
But the big difference is that granular materials tend tosegregate
Rob Sturman Granular mixing
Mixing
Mixing of granular materials:is important — Science 125th anniversary identifiedgranular flow as one of the 125 big questions in Scienceis ubiquitous — pharmaceuticals, food industry, ceramics,metallurgy, constructionwas initially explained by analogies with fluid mixing —hence terms like granular shear and granular diffusion
But the big difference is that granular materials tend tosegregate
Rob Sturman Granular mixing
Mixing
Mixing of granular materials:is important — Science 125th anniversary identifiedgranular flow as one of the 125 big questions in Scienceis ubiquitous — pharmaceuticals, food industry, ceramics,metallurgy, constructionwas initially explained by analogies with fluid mixing —hence terms like granular shear and granular diffusion
But the big difference is that granular materials tend tosegregate
Rob Sturman Granular mixing
Mixing
Mixing of granular materials:is important — Science 125th anniversary identifiedgranular flow as one of the 125 big questions in Scienceis ubiquitous — pharmaceuticals, food industry, ceramics,metallurgy, constructionwas initially explained by analogies with fluid mixing —hence terms like granular shear and granular diffusion
But the big difference is that granular materials tend tosegregate
Rob Sturman Granular mixing
Segregation
Granular materials segregate by (at least) 2 mechanisms:
Percolation — little particles fall through the gaps of bigparticlesBuoyancy — less dense particles tend to rise
The Brazil Nut effect
Rob Sturman Granular mixing
Segregation
Granular materials segregate by (at least) 2 mechanisms:
Percolation — little particles fall through the gaps of bigparticlesBuoyancy — less dense particles tend to rise
The Brazil Nut effect
Rob Sturman Granular mixing
The draft lottery
In 1969, the Selective Service Systemof the USA held a lottery to determinethe order of draft into the U.S. Army forthe Vietnam War.Days of the year numbered 1 to 366drawn once to assign lottery number,and again to determine draft number.
Rob Sturman Granular mixing
The draft lottery
In 1969, the Selective Service Systemof the USA held a lottery to determinethe order of draft into the U.S. Army forthe Vietnam War.Days of the year numbered 1 to 366drawn once to assign lottery number,and again to determine draft number.
Rob Sturman Granular mixing
The draft lottery
0
50
100
150
200
250
300
350
0 50 100 150 200 250 300 350
Lotte
ry r
ank
Birthday
Rob Sturman Granular mixing
Tumbler Mixers
Rob Sturman Granular mixing
Different tumbler geometries
Rob Sturman Granular mixing
Flow regimes
[from S. W. Meier et al., 2007]
Rob Sturman Granular mixing
Tumblers
[from S. W. Meier et al., 2007]
Rob Sturman Granular mixing
[Zuriguel, I., Gray, J.M.N.T., Peixinho, J. & T. Mullin (2006).Phys. Rev. E 73, 061302.]
Rob Sturman Granular mixing
Tumblers
Modelling percolation and buoyancy
[from S. W. Meier et al., 2007]
Rob Sturman Granular mixing
2D circular tumblers
In the bulk
r = 0, θ = ω
In the flowing layer
x = γ(δ(x)+y), y = ωxy/δ(x)
The flowing layer hasshape
δ(x) = δ0
√1 − x2/L2
Rob Sturman Granular mixing
Constant rotation rate
At constant rotation rateparticle streamlines form closed loops passing throughflowing layersteady, divergence-free, integrablecan transform to action–angle coordinates ρ, φtrajectories in action–angle coordinates given by:
ρ = 0φ = 2π/T (ρ)
taking a time τ -map gives a twist map
P(ρ, φ) = (ρ, φ+ 2πτ/T (ρ))
Rob Sturman Granular mixing
Constant rotation rate
At constant rotation rateparticle streamlines form closed loops passing throughflowing layersteady, divergence-free, integrablecan transform to action–angle coordinates ρ, φtrajectories in action–angle coordinates given by:
ρ = 0φ = 2π/T (ρ)
taking a time τ -map gives a twist map
P(ρ, φ) = (ρ, φ+ 2πτ/T (ρ))
Rob Sturman Granular mixing
Constant rotation rate
At constant rotation rateparticle streamlines form closed loops passing throughflowing layersteady, divergence-free, integrablecan transform to action–angle coordinates ρ, φtrajectories in action–angle coordinates given by:
ρ = 0φ = 2π/T (ρ)
taking a time τ -map gives a twist map
P(ρ, φ) = (ρ, φ+ 2πτ/T (ρ))
Rob Sturman Granular mixing
Constant rotation rate
At constant rotation rateparticle streamlines form closed loops passing throughflowing layersteady, divergence-free, integrablecan transform to action–angle coordinates ρ, φtrajectories in action–angle coordinates given by:
ρ = 0φ = 2π/T (ρ)
taking a time τ -map gives a twist map
P(ρ, φ) = (ρ, φ+ 2πτ/T (ρ))
Rob Sturman Granular mixing
Constant rotation rate
At constant rotation rateparticle streamlines form closed loops passing throughflowing layersteady, divergence-free, integrablecan transform to action–angle coordinates ρ, φtrajectories in action–angle coordinates given by:
ρ = 0φ = 2π/T (ρ)
taking a time τ -map gives a twist map
P(ρ, φ) = (ρ, φ+ 2πτ/T (ρ))
Rob Sturman Granular mixing
Variable rotation rate
Break the integrability by varying the rate of angular rotationSinusoidal forcing has been well-studied.
[Fiedor and Ottino, JFM 255 2005]
Rob Sturman Granular mixing
Variable rotation rate
[Fiedor and Ottino, JFM 255 2005]
Rob Sturman Granular mixing
Variable rotation rate
Key idea is that streamlines changes and cross
[Fiedor and Ottino, JFM 255 2005]
Rob Sturman Granular mixing
Piecewise constant rotation rate
Simplify the forcing by using a blinking flow
ω =
ωb = ω + ω for iτ < t < (i + 1/4)τωa = ω − ω for (i + 1/4)τ < t < (i + 3/4)τωb = ω + ω for (i + 3/4)τ < t < (i + 1)τ
Alternate the angular velocity between ωa and ωb.
Rob Sturman Granular mixing
Poincaré sections
N = 2 N = 4
N = 6 N = 8
Rob Sturman Granular mixing
Blinking experiments
Rob Sturman Granular mixing
Linked Twist Maps on the plane
Domain is two intersect-ing annuli with two dis-tinct regions of intersec-tion
Rob Sturman Granular mixing
Linked Twist Maps on the plane
The action of a twist mapis to take a line...
Rob Sturman Granular mixing
Linked Twist Maps on the plane
... and twist it around theannulus.Then do the same withpoints in the other annu-lus.
Proof of ergodic mixing due to Burton & Easton (1980),Devaney (1980), Wojtkowski (1980), Przytycki (1983)
Rob Sturman Granular mixing
Linked Twist Maps on the plane
... and twist it around theannulus.Then do the same withpoints in the other annu-lus.
Proof of ergodic mixing due to Burton & Easton (1980),Devaney (1980), Wojtkowski (1980), Przytycki (1983)
Rob Sturman Granular mixing
Linked Twist Maps on the plane
... and twist it around theannulus.Then do the same withpoints in the other annu-lus.
Proof of ergodic mixing due to Burton & Easton (1980),Devaney (1980), Wojtkowski (1980), Przytycki (1983)
Rob Sturman Granular mixing
The Blinking Vortex
Rob Sturman Granular mixing
The Blinking Vortex
Rob Sturman Granular mixing
The Blinking Vortex
Rob Sturman Granular mixing
The Blinking Vortex
Rob Sturman Granular mixing
Microfluidics — patterned walls
from [Stroock, A. D. et al., Science 295, 647–651 (2002)]
Rob Sturman Granular mixing
Microfluidics — electroosmotic flow
from [Qian, S. & Bau, H. H., Anal. Chem., 74, 3616–3625 (2002)]
Rob Sturman Granular mixing
Streamline crossing structure
Rob Sturman Granular mixing
3-dimensional spherical tumbler
An obvious way to introduce some transversality...
Rob Sturman Granular mixing
Rotation about the z-axis
Solid body rotation in the bulk:
x = ωyy = −ωxz = 0
Shear in the flowing layer:
x = γ1(δ1(x , z) + y)
y = ω1xy/δ1(x , z)
z = 0
Boundary of flowing layer and bulk:
δ1(x , z) = δ0
√1 − x2/L2
=√ω1/γ1
√R2 − x2 − z2
Rob Sturman Granular mixing
Rotation about the z-axis
Solid body rotation in the bulk:
x = ωyy = −ωxz = 0
Shear in the flowing layer:
x = γ1(δ1(x , z) + y)
y = ω1xy/δ1(x , z)
z = 0
Boundary of flowing layer and bulk:
δ1(x , z) = δ0
√1 − x2/L2
=√ω1/γ1
√R2 − x2 − z2
Rob Sturman Granular mixing
Rotation about the z-axis
Solid body rotation in the bulk:
x = ωyy = −ωxz = 0
Shear in the flowing layer:
x = γ1(δ1(x , z) + y)
y = ω1xy/δ1(x , z)
z = 0
Boundary of flowing layer and bulk:
δ1(x , z) = δ0
√1 − x2/L2
=√ω1/γ1
√R2 − x2 − z2
Rob Sturman Granular mixing
Rotation about the x-axis
Solid body rotation in the bulk:
x = 0y = −ωzz = ωy
Shear in the flowing layer:
x = 0y = ω2zy/δ2(x , z)
z = γ2(δ2(x , z) + y)
Boundary of flowing layer and bulk:
δ2(x , z) = δ0
√1 − z2/L2
=√ω2/γ2
√R2 − x2 − z2
Rob Sturman Granular mixing
Rotation about the x-axis
Solid body rotation in the bulk:
x = 0y = −ωzz = ωy
Shear in the flowing layer:
x = 0y = ω2zy/δ2(x , z)
z = γ2(δ2(x , z) + y)
Boundary of flowing layer and bulk:
δ2(x , z) = δ0
√1 − z2/L2
=√ω2/γ2
√R2 − x2 − z2
Rob Sturman Granular mixing
Rotation about the x-axis
Solid body rotation in the bulk:
x = 0y = −ωzz = ωy
Shear in the flowing layer:
x = 0y = ω2zy/δ2(x , z)
z = γ2(δ2(x , z) + y)
Boundary of flowing layer and bulk:
δ2(x , z) = δ0
√1 − z2/L2
=√ω2/γ2
√R2 − x2 − z2
Rob Sturman Granular mixing
Dynamical properties I
TheoremIf ω1/γ1 = ω2/γ2 then motion of a particle is constrained to asingle hemispherical surface.
Rob Sturman Granular mixing
Dynamical properties II
TheoremPeriod 1 points for rotation about the x-axis form a bowl in theshape of a prolate spheroid.
Rob Sturman Granular mixing
Intersection of bowl and spheroid
Rob Sturman Granular mixing
Experiments
Experiments...are hard — how do you see what’s happening inside a spherefilled with a granular material?
Rob Sturman Granular mixing
Experiments
Experiments...are hard — how do you see what’s happening inside a spherefilled with a granular material?
Rob Sturman Granular mixing
Rob Sturman Granular mixing
Rob Sturman Granular mixing
Piecewise isometries
[Goetz, 2003]
Rob Sturman Granular mixing
Outstanding problems
3 dimensional transport through the hemispherethe role of segregationthe role of the dynamics of piecewise isometrieshow to measure, or even see, all the above in anexperiment
Rob Sturman Granular mixing
Outstanding problems
3 dimensional transport through the hemispherethe role of segregationthe role of the dynamics of piecewise isometrieshow to measure, or even see, all the above in anexperiment
Rob Sturman Granular mixing
Outstanding problems
3 dimensional transport through the hemispherethe role of segregationthe role of the dynamics of piecewise isometrieshow to measure, or even see, all the above in anexperiment
Rob Sturman Granular mixing
Outstanding problems
3 dimensional transport through the hemispherethe role of segregationthe role of the dynamics of piecewise isometrieshow to measure, or even see, all the above in anexperiment
Rob Sturman Granular mixing