Post on 25-Jul-2020
Viscoelastic fluid flow past a confined cylinder in microfluidic devices
Vera M. Ribeiroa), Paulo M. Coelhob), Fernando T. Pinhob) and Manuel A. Alvesa)
Faculty of Engineering - University of Porto - Portugal CEFT - a) Dep. of Chemical Eng.; b) Dep. Mechanical Eng.;
XVIth International Congress on Rheology
August, 05 – 10, 2012 • Lisbon, Portugal
Outline
Objectives
Experimental
Rheological characterization
Numerical method
Results
Conclusions
V.M. Ribeiro, P.M. Coelho, F.T. Pinho, M.A. Alves Viscoelastic fluid flow past a confined cylinder in microfluidic devices XVIth ICR - 07 August 2012 • Lisbon, Portugal
Set-up Techniques
Objectives
V.M. Ribeiro, P.M. Coelho, F.T. Pinho, M.A. Alves Viscoelastic fluid flow past a confined cylinder in microfluidic devices XVIth ICR - 07 August 2012 • Lisbon, Portugal
Benchmark problem in computational rheology(Brown and McKinley,
1994)
Newtonian and viscoelastic flow past
a confined cylinder
Micro-scale increase De
decreases Re
highly elastic effects without inertial effects
Blockage ratio of 50%
Three-dimensional effects in laminar flow past a confined cylinderRibeiro, V.M., Coelho, P.M., Pinho, F.T., Alves, M.A.
Chemical Engineering Science (2012)
Previous work:
Three dimensional effects and stability of viscoelastic fluid flow past a confined cylinder
V.M. Ribeiro, F.T. Pinho, P.M. Coelho and M.A. Alves83rd Annual Meeting of SoR (2011).
Present work:
Macro-scale
Objectives
V.M. Ribeiro, P.M. Coelho, F.T. Pinho, M.A. Alves Viscoelastic fluid flow past a confined cylinder in microfluidic devices XVIth ICR - 07 August 2012 • Lisbon, Portugal
Shear-thinningShear-thinningto assess influence of aspect ratio - AR
to assess influence of aspect ratio - AR
NewtonianNewtonian
BogerBoger for BR = 50 %
• Important for validation of 3D numerical codes
Experimental study:
Numerical study:
• To compared with the experimental results (Newtonian and Boger)
BR = 50%
Experimental - Microchannels
V.M. Ribeiro, P.M. Coelho, F.T. Pinho, M.A. Alves Viscoelastic fluid flow past a confined cylinder in microfluidic devices XVIth ICR - 07 August 2012 • Lisbon, Portugal
D = 100 μmH = 200 μm
2.0
1.0
0.5Flow direction
zx
yCoordinate
system
퐴푅 =퐷푒푝ℎ푡(ℎ)
퐷푖푎푚푒푡푒푟(퐷)퐵푅 =퐷푖푎푚푒푡푒푟(퐷)푊푖푑ℎ푡(퐻)
AR h = 200 μm
h = 100 μm
h = 50 μm
Experimental - Techniques
Flow visualizations
Velocity measurements
Streak-line photography
μPIV Micro-particle Image Velocimetry
V.M. Ribeiro, P.M. Coelho, F.T. Pinho, M.A. Alves Viscoelastic fluid flow past a confined cylinder in microfluidic devices XVIth ICR - 07 August 2012 • Lisbon, Portugal
Inverted epifluorescence microscope
(DMI 5000M, Leica Microsystems)
Rheological characterization
Fluid PAA(ppm)
Glycerine(%)
Water(%)
NaCl(%)
Newtonian - 40 60 -
Shear-thinning 1000 - 99.9 -
Boger PAA200 200 85 13.98 1.0
Newtonian
η20ºC = 0.00360 Pa.s
Boger Fluid
hp = 0.042 Pa.s
hs = 0.123 Pa·s
λ = 82.2 ms
Oldrody- B model
Shear Rheometer
Extensional Rheometer
V.M. Ribeiro, P.M. Coelho, F.T. Pinho, M.A. Alves Viscoelastic fluid flow past a confined cylinder in microfluidic devices XVIth ICR - 07 August 2012 • Lisbon, Portugal
Cone-plate system; D = 75 mm; 1º angle;
(Anton Paar, model Physica MCR 301)
(Haake CaBER 1, Thermo Scientific)
Seeded with 1 µm fluorescent polystyrene tracer particles
(Nile Red, Molecular Probes, Invitrogen, Ex/Em: 520/580 nm)
Numerical method
V.M. Ribeiro, P.M. Coelho, F.T. Pinho, M.A. Alves Viscoelastic fluid flow past a confined cylinder in microfluidic devices XVIth ICR - 07 August 2012 • Lisbon, Portugal
0 u
Mass conservation: Momentum conservation:
Discretization:
Diffusive terms – Central differences
Convective terms – High-resolution scheme – CUBISTA (Alves et al., 2003)
Finite-volume method (Oliveira et al., 1998)
2 h
u uu τ uspt
Constitutive Equation:
T T h
ττ uτ u u τ u u τPt+ + +
0 20 40 60 80 100 120 140 1600
2
4
6
AR = 0.5
AR = 1
L v /
R
Re
AR = 2
Results - Newtonian
V.M. Ribeiro, P.M. Coelho, F.T. Pinho, M.A. Alves Viscoelastic fluid flow past a confined cylinder in microfluidic devices XVIth ICR - 07 August 2012 • Lisbon, Portugal
• Lv decreases with AR
• Lv increases with Re
AR = 2 AR = 1 AR = 0.5
Re = 40
Lv
Results - Newtonian
V.M. Ribeiro, P.M. Coelho, F.T. Pinho, M.A. Alves Viscoelastic fluid flow past a confined cylinder in microfluidic devices XVIth ICR - 07 August 2012 • Lisbon, Portugal
-10 -5 0 5 10 15 20-0.5
0.0
0.5
1.0
1.5
2.0
2.5
u / U
x / R-10 -5 0 5 10 15 20
x / R-10 -5 0 5 10 15 20
x / R
AR = 2 AR = 1 AR = 0.5
Re = 40 Re = 40Re = 40
Re = 10 Re = 10 Re = 10
The development lenghts required increase with Re and AR
The fully-developed velocity is independent of Re and decreases as AR decrease
Due to the geometric
confinement
• Lv increases with Re and decreases with AR
V.M. Ribeiro, P.M. Coelho, F.T. Pinho, M.A. Alves Viscoelastic fluid flow past a confined cylinder in microfluidic devices XVIth ICR - 07 August 2012 • Lisbon, Portugal
Results – Boger
Appearance of an elastic instability at a Dec
Symmetric
Asymmetric and stable
De = 1.0
De = 40.0
Unstable
depends on AR
Results - Boger
V.M. Ribeiro, P.M. Coelho, F.T. Pinho, M.A. Alves Viscoelastic fluid flow past a confined cylinder in microfluidic devices XVIth ICR - 07 August 2012 • Lisbon, Portugal
AR = 2 AR = 1 AR = 0.5
Appearance of an elastic instability
at a Dec
Symmetric
Asymmetric and Stable
De = 1.0
De = 50.0
Unstable
Dec ≈ 9.5Dec ≈ 12.0 Dec ≈ 9.5
V.M. Ribeiro, P.M. Coelho, F.T. Pinho, M.A. Alves Viscoelastic fluid flow past a confined cylinder in microfluidic devices XVIth ICR - 07 August 2012 • Lisbon, Portugal
Results - Boger
De = 4.8De = 19.3 De = 35.2
AR = 1
V.M. Ribeiro, P.M. Coelho, F.T. Pinho, M.A. Alves Viscoelastic fluid flow past a confined cylinder in microfluidic devices XVIth ICR - 07 August 2012 • Lisbon, Portugal
Results – Boger
AR = 1 AR = 0.5AR = 2
De = 33.8
V.M. Ribeiro, P.M. Coelho, F.T. Pinho, M.A. Alves Viscoelastic fluid flow past a confined cylinder in microfluidic devices XVIth ICR - 07 August 2012 • Lisbon, Portugal
Results – Boger
AR = 2
The development lenghts required increase with De
AR = 1 AR = 0.5
-15 -10 -5 0 5 10 15
x / R-15 -10 -5 0 5 10 15
0.0
0.5
1.0
1.5
2.0
2.5
u / U
x / R
The deceleration is independent of De The fully-developed velocity is independent of De and
descreases as AR decrease
De = 9.6
De = 1.2De = 1.2
De = 9.6
De
The numercial results predicted well the
experimental results
-15 -10 -5 0 5 10 150.0
0.5
1.0
1.5
2.0
2.5
x / R
Elastic effect
V.M. Ribeiro, P.M. Coelho, F.T. Pinho, M.A. Alves Viscoelastic fluid flow past a confined cylinder in microfluidic devices XVIth ICR - 07 August 2012 • Lisbon, Portugal
Results – Shear-thinning
Appearance of an elastic instability at a Dec
Symmetric flow
Asymmetric and time-dependent
De = 10.0
De = 1500
Unstable
depends on AR
V.M. Ribeiro, P.M. Coelho, F.T. Pinho, M.A. Alves Viscoelastic fluid flow past a confined cylinder in microfluidic devices XVIth ICR - 07 August 2012 • Lisbon, Portugal
Results – Shear-thinning
AR = 2 AR = 1 AR = 0.5
Dec ≈ 200
De = 10.0
Dec ≈ 290
De = 3500
Dec ≈ 220Appearance of an elastic instability
at a Dec
Symmetric
Asymmetric and time-dependent
Unstable
V.M. Ribeiro, P.M. Coelho, F.T. Pinho, M.A. Alves Viscoelastic fluid flow past a confined cylinder in microfluidic devices XVIth ICR - 07 August 2012 • Lisbon, Portugal
Results – Shear-thinning
De = 670
AR = 0.5AR = 1AR = 2
V.M. Ribeiro, P.M. Coelho, F.T. Pinho, M.A. Alves Viscoelastic fluid flow past a confined cylinder in microfluidic devices XVIth ICR - 07 August 2012 • Lisbon, Portugal
Results – Shear-thinning
AR = 2 AR = 0.5AR = 1
-15 -10 -5 0 5 10 150.0
0.5
1.0
1.5
2.0
u / U
x / R-15 -10 -5 0 5 10 15
0.0
0.5
1.0
1.5
2.0
u / U
x / R
-15 -10 -5 0 5 10 150.0
0.5
1.0
1.5
2.0
u / U
x / R
De = 220
De = 56
The shear-thinning of the fluid leads to a decrease of the
fully-developed velocity
The deceleration occurs further for higher De
The development lenghts required increases with De
Elastic effect
The fully-developed velocity is independent of De and
decreases as AR decrease
DeDe = 220
De = 56
De = 220
De = 56
Conclusions
V.M. Ribeiro, P.M. Coelho, F.T. Pinho, M.A. Alves Viscoelastic fluid flow past a confined cylinder in microfluidic devices XVIth ICR - 07 August 2012 • Lisbon, Portugal
Newtonianfluid
Viscoelastic fluids
Recirculation lenght decreases with AR
The deceleration (upstream) and the recovery (dowstream) of the velocity depends on AR and Re
Dec decrease as AR decrease
The development lenghts required for the fully-developed velocity increases with De
The fully-developed velocity:
The shear-thinning behavior of the fluid leads to a decrease of the fully-developed velocity
decreases as AR decrease is independent of De due to the geometric
confinement
due to the elasticity of the fluids
Future Work
V.M. Ribeiro, P.M. Coelho, F.T. Pinho, M.A. Alves Viscoelastic fluid flow past a confined cylinder in microfluidic devices XVIth ICR - 07 August 2012 • Lisbon, Portugal
Newtonian and viscoelastic fluid flow in microfluidic devices
Blockage ratio, BR = 50 %
Effect of blockage ratio, BR
50 %
2 1 0.5
Effect of aspect ratio, AR:
25 %
75 %
Acknoledgements
V.M. Ribeiro, P.M. Coelho, F.T. Pinho, M.A. Alves Viscoelastic fluid flow past a confined cylinder in microfluidic devices XVIth ICR - 07 August 2012 • Lisbon, Portugal
Fundação para a Ciência e a Tecnologia (FCT),COMPETE and FEDER for the financial support throughprojects:
• Scholarship SFRH/BD/44737/2008
• Project PTDC/ECM/70744/2006
• PTDC/EME-MFE/114322/2009
CEFT group