simulation model of drying colloidal suspension on...
TRANSCRIPT
The 3rd Asian Coating Workshop, 2011.7.4-5 /13
SIMULATION MODEL OF DRYING COLLOIDAL
SUSPENSION ON SUBSTRATE
Masahiro Fujita, Osamu Koike, Yukio Yamaguchi
Department of Chemical System Engineering,The University of Tokyo, Japan
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The 3rd Asian Coating Workshop, 2011.7.4-5 /13
OUTLINE
Continuous coating of colloidal suspension on substrate
Direct simulation model for drying colloidal suspension
Demonstration of present simulation model
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The 3rd Asian Coating Workshop, 2011.7.4-5 /13
CONTINUOUS COATING ON SUBSTRATE
film
suspension
structure formation
flow
drying
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The 3rd Asian Coating Workshop, 2011.7.4-5 /13
PECLÉT NUMBERS
coating Peclét number drying Peclét number
Peclét numbers ratio
Both flow and drying influence structure formation
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The 3rd Asian Coating Workshop, 2011.7.4-5 /13
OBJECTIVES OF THIS STUDY
Develop direct simulation model for drying colloidal suspension
Perform flow simulations of colloidal suspension on sliding substrate with drying of solvent
Quantify coating-drying dynamics
structure of particles
variable drying rate
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The 3rd Asian Coating Workshop, 2011.7.4-5 /13
DIRECT SIMULATION MODEL
Solves gas-liquid two phase flow on lattice using VOF (volume of fluid) method
Solves translational/rotational motion of particles subject to contact, DLVO, capillary interactions
Couples motion of particles with flow of solvent using immersed boundary method
Interparticle hydrodynamic interaction is included without analytical model
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The 3rd Asian Coating Workshop, 2011.7.4-5 /13
EQUATIONS OF FLUID MOTION
fluctuating stress
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acceleration
f = 0
f = 1local drying velocity
The 3rd Asian Coating Workshop, 2011.7.4-5 /13
EQUATIONS OF PARTICLE MOTION
acceleration
acceleration
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The 3rd Asian Coating Workshop, 2011.7.4-5 /13
SIMULATION CONDITION
drying
sliding substrate
0.3 μm
periodic boundary
1 μm 1 μm
d = 0.1 μm, φ0 = 20 vol%, ζ = -50/0 mV
c =13 cm/s, e =1.4 cm/s Pec / Ped = 1
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The 3rd Asian Coating Workshop, 2011.7.4-5 /13
QUANTIFICATION OF STRUCTURE
Non-dimensional Boundary Area (NBA)
NBA=1 : complete-dispersed
NBA=0 : 3D hexagonal close-packed
NBAsurface area of aggregates
total surface area of particles=
k : coordinate numbern(k) : number of particles with coordinate number of kN : total number of particles
NBA=0.5 : 2D hexagonal close-packed
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The 3rd Asian Coating Workshop, 2011.7.4-5 /13
STRUCTURE OF PARTICLES
plan
side
NBA vs interface height
ζ = -50 mVζ = 0 mV
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ζ = -50 mV
drying inducedaggregation
potential inducedaggregation
The 3rd Asian Coating Workshop, 2011.7.4-5 /13
VARIABLE DRYING RATE
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drying rate vs interface height
pure solventcalculated(ζ=-50mV)smoothed
The 3rd Asian Coating Workshop, 2011.7.4-5 /13
CONCLUSION
Developed direct simulation model for drying colloidal suspension
Quantify structure formation of particles using NBA
Quantify variable drying rate in which constant rate of drying changes to decreasing rate of drying.
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