Structural evolution of colloidal gels at intermediate volume fraction under start-up of shear flow

Soft Matter ◽  
2013 ◽  
Vol 9 (48) ◽  
pp. 11650 ◽  
Author(s):  
Jun Dong Park ◽  
Kyung Hyun Ahn
Keyword(s):  
Shear Flow ◽  
Volume Fraction ◽  
Structural Evolution ◽  
Colloidal Gels ◽  
Start Up

Yield of reversible colloidal gels during flow start-up: release from kinetic arrest

Soft Matter ◽  
2018 ◽  
Vol 14 (24) ◽  
pp. 5048-5068 ◽  
Author(s):  
Lilian C. Johnson ◽  
Benjamin J. Landrum ◽  
Roseanna N. Zia
Keyword(s):  
Shear Stress ◽  
Shear Flow ◽  
Network Structure ◽  
Colloidal Gels ◽  
Start Up ◽  
Kinetic Arrest

Yield of colloidal gels during start-up of shear flow is characterized by an overshoot in shear stress that accompanies changes in network structure.

Elasticity of colloidal gels: structural heterogeneity, floppy modes, and rigidity

Soft Matter ◽  
2021 ◽  
Author(s):  
D. Zeb Rocklin ◽  
Lilian C Hsiao ◽  
Megan E Szakasits ◽  
Michael J Solomon ◽  
Xiaoming Mao
Keyword(s):  
Coordination Number ◽  
Volume Fraction ◽  
Structural Parameters ◽  
Structural Heterogeneity ◽  
Colloidal Gels ◽  
Shear Moduli ◽  
Rheological Measurements

Rheological measurements of model colloidal gels reveal that large variations in the shear moduli as colloidal volume-fraction changes are not reflected by simple structural parameters such as the coordination number,...

scholarly journals Start-up shear flow of a shear-thinning fluid that approximates the response of viscoplastic fluids

2022 ◽  
Vol 412 ◽  
pp. 126571
Author(s):  
Sai Manikiran Garimella ◽  
Mohan Anand ◽  
Kumbakonam R. Rajagopal
Keyword(s):  
Shear Flow ◽  
Shear Thinning ◽  
Viscoplastic Fluids ◽  
Start Up ◽  
Shear Thinning Fluid

Microscopic dynamics and rheology of colloidal gels

2016 ◽  
Author(s):  
Εσμαΐλ Μοκίμι
Keyword(s):  
Colloidal Gels ◽  
Start Up ◽  
Microscopic Dynamics

Στην παρούσα διδακτορική διατριβή, πραγματοποιείται μελέτη της γραμμικής και μη γραμμικής ρεολογικής συμπεριφοράς πυκνών κολλοειδών διαλυμάτων με ελκυκτικές αλληλεπιδράσεις. Για την πλήρη κατανόηση της σχέσης μεταξύ της μικροδομής των κολλοειδών αυτών διαλυμάτων με τις μηχανικές τους ιδιότητες πραγματοποιήθηκαν ρεολογικές πειραματικές, οι οποίες συγκρίθηκαν με προσομοιώσεις Brownian δυναμικής. Το πειραματικό μοντέλο που χρησιμοποιήθηκε αποτελείται από ένα μίγμα κολλοειδών σκληρών σφαιρών (PMMA) και γραμμικών πολυμερικών αλυσίδων που δεν απορροφούνται από το διαλύτη, οι οποίες παίζουν το ρόλο των depletants. Μελετήθηκαν διάφορες συγκεντρώσεις σωματιδίων και μεγέθους ελκτικών αλληλεπιδράσεων μεταξύ αραιών κολλειδών γελών και των πυκνών κολλοειδών υάλων. Προκειμένου να εξάγουμε πληροφορίες για τη ρεολογική δομή των υπό μελέτη συστημάτων, χρησιμοποιήθηκαν προσομοιώσεις Brownian δυναμικής. Η παρούσα μελέτη αποτελείται από τέσσερα μέρη. Αρχικά διερευνήσαμε τη ρεολογική διαρροή κολλοειδών ελκτικών υάλων υπό συνθήκες start-up διατμητικής ροής. Μελετήθηκε η επίδραση της μεταβολής του μεγέθους των ελκτικών δυνάμεων για μία συγκεκριμένη συγκέντρωση (φ=0.62) σωματιδίων. Εν συνεχεία, μελετήθηκε η γραμμική και μη-γραμμική ρεολογική συμπεριφορά κολλοειδών γελών διαφόρων συγκεντρώσεων, η γήρανση των αντίστοιχων γελών, καθώς και διαφορετική δυναμική δεσμών μεταξύ των σωματιδίων. Στο τρίτο μέρος, μελετήθηκε η πτωτική εξέλιξη της διατμητικής τάσης με το χρόνο ύστερα από την παύση σταθερής διατμητικής καταπόνησης ενδιάμεσης συγκέντρωσης (φ=0.44) διαλύματος κολλοειδούς γέλης μέσω ρεολογίας και BD προσομοιώσεων. Στο τέλος, διερευνήθηκε η σχέση μεταξύ δομικών και μηχανικών ιδιοτήτων κολλοειδούς γέλης υπό συνθήκες σταθερούς και ταλαντωτικής διατμητικής ροής, καθώς και παύσης αυτής με τη χρήση πειραμάτων και προσομοιώσεων.

Double Stress Overshoot in Start-Up of Simple Shear Flow of Entangled Comb Polymers

2013 ◽  
Vol 2 (7) ◽  
pp. 601-604 ◽  
Author(s):  
F. Snijkers ◽  
D. Vlassopoulos ◽  
G. Ianniruberto ◽  
G. Marrucci ◽  
H. Lee ◽  
...  
Keyword(s):  
Shear Flow ◽  
Simple Shear ◽  
Simple Shear Flow ◽  
Comb Polymers ◽  
Stress Overshoot ◽  
Start Up

Structural Evolution of Colloidal Gels During Constricted Microchannel Flow

Langmuir ◽  
2010 ◽  
Vol 26 (9) ◽  
pp. 6102-6107 ◽  
Author(s):  
Jacinta C. Conrad ◽  
Jennifer A. Lewis
Keyword(s):  
Structural Evolution ◽  
Colloidal Gels ◽  
Microchannel Flow

The effect of boundaries on the plane Couette flow of granular materials: a bifurcation analysis

1999 ◽  
Vol 397 ◽  
pp. 203-229 ◽  
Author(s):  
P. R. NOTT ◽  
M. ALAM ◽  
K. AGRAWAL ◽  
R. JACKSON ◽  
S. SUNDARESAN
Keyword(s):  
Shear Flow ◽  
Granular Materials ◽  
Volume Fraction ◽  
High Amplitude ◽  
Numerical Continuation ◽  
Infinite Plane ◽  
Wall Boundary Conditions ◽  
The Mean ◽  
The Stability ◽  
Oriented Parallel

The tendency of granular materials in rapid shear ow to form non-uniform structures is well documented in the literature. Through a linear stability analysis of the solution of continuum equations for rapid shear flow of a uniform granular material, performed by Savage (1992) and others subsequently, it has been shown that an infinite plane shearing motion may be unstable in the Lyapunov sense, provided the mean volume fraction of particles is above a critical value. This instability leads to the formation of alternating layers of high and low particle concentrations oriented parallel to the plane of shear. Computer simulations, on the other hand, reveal that non-uniform structures are possible even when the mean volume fraction of particles is small. In the present study, we have examined the structure of fully developed layered solutions, by making use of numerical continuation techniques and bifurcation theory. It is shown that the continuum equations do predict the existence of layered solutions of high amplitude even when the uniform state is linearly stable. An analysis of the effect of bounding walls on the bifurcation structure reveals that the nature of the wall boundary conditions plays a pivotal role in selecting that branch of non-uniform solutions which emerges as the primary branch. This demonstrates unequivocally that the results on the stability of bounded shear flow of granular materials presented previously by Wang et al. (1996) are, in general, based on erroneous base states.

ON THE EXTENDED RUTGERS–DELAWARE RULE FOR MR SUSPENSIONS UNDER MAGNETIC FIELDS

2006 ◽  
Vol 20 (05) ◽  
pp. 579-592 ◽  
Author(s):  
Y. B. YANG ◽  
G. CHEN ◽  
L. LI ◽  
W. H. LI
Keyword(s):  
Magnetic Fields ◽  
Shear Flow ◽  
Magnetic Particles ◽  
Volume Fraction ◽  
Complex Viscosity ◽  
Shift Factor ◽  
Oscillatory Shear ◽  
Oscillatory Shear Flow ◽  
Steady Shear Flow ◽  
Series Of Experiments

The interrelation between apparent viscosity in steady shear flow and complex viscosity in oscillatory shear flow for magnetorheological (MR) suspensions is investigated. Series of experiments have been conducted using a MR rheometer. An extended Rutgers–Delaware rule is proposed, in which an effective shear rate for oscillatory shear flow is defined as ωΔh. Here ωΔh is the shift factor dependent on strain amplitude (γ0), which was found to be similar for different MR suspensions under different magnetic fields. At high strain amplitudes (γ0≥100%), Δh≈γ0, the Rutgers–Delaware rule is approximately obeyed. At low strain amplitudes (γ0<100%), the curves of Δh fall between the line of the Cox–Merz rule and that of the Rutgers–Delaware rule. The curve of Δh at low strain amplitudes depends on the ingredients of the MR suspension. For samples with the same ingredients, a unified curve of Δh can be identified in a range of magnetic fields and/or for a range of volume fraction of magnetic particles.

Nucleation and Growth of Liquid Droplets Under a Shear Flow

1991 ◽  
Vol 248 ◽  
Author(s):  
F. Perrot ◽  
T. Baumberger
Keyword(s):  
Shear Flow ◽  
Volume Fraction ◽  
Liquid Droplets ◽  
Subsequent Growth ◽  
Two Phase ◽  
Angle Scattering ◽  
Steady Shear Flow ◽  
Mixture Volume ◽  
New Phase

AbstractPhase separation in an off-critical binary mixture is studied under an uniform and steady shear flow. The nucleation and subsequent growth of droplets in aweakly supersaturated mixture (volume fraction of the new phase smaller than 10%) is studied by small angle scattering and turbidity measurements. The completion of the nucleation process is shown to be accelerated by the shear flow. At very low supersaturation, a strong effect of shear is detected which can be related to shear-triggered nucleation. In situ measurements ’of the surface tension between the two phase-separating phases obtained by studying the deformation and tilt of the growing droplets is discussed.

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