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.

THE CONTRIBUTION OF COLUMNAR STRUCTURE TO THE STRESS IN ER POLYMERIC BLENDS IN A SHEAR FLOW

2002 ◽  
Vol 16 (17n18) ◽  
pp. 2542-2547
Author(s):  
P. RIHA ◽  
J. TAKIMOTO ◽  
Y. MASUBUCHI ◽  
K. KOYAMA
Keyword(s):  
Experimental Data ◽  
Stochastic Process ◽  
Shear Stress ◽  
Shear Flow ◽  
Columnar Structure ◽  
Viscous Deformation ◽  
Polymeric Blends ◽  
Start Up ◽  
Dominant Feature ◽  
Viscous Polymer

The bridging of electrodes by the columns of highly viscous polymer is dominant feature of the response of most electro-rheological liquid polymeric blends to the imposed electric field. To link the columnar structure and its deformation to the macroscopic shear stress, the transitory process of structure reorganization is described as a stochastic process determining rheological properties of the blend. The shear stress predictions are compared to the experimental data for steady and start up shear flows. The data support the assumption that only viscous deformation prevails in shear flow.

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

Tracings of Behavior of Myoblasts Cultured Under Couette Type of Shear Flow Between Parallel Disks

2021 ◽  
Author(s):  
Shigehiro Hashimoto ◽  
Hiroki Yonezawa
Keyword(s):  
Shear Stress ◽  
Shear Flow ◽  
Rotating Disk ◽  
Time Lapse ◽  
Mechanical Stimuli ◽  
Parallel Disks ◽  
Before And After ◽  
A Cell

Abstract A cell deforms and migrates on the scaffold under mechanical stimuli in vivo. In this study, a cell with division during shear stress stimulation has been observed in vitro. Before and after division, both migration and deformation of each cell were analyzed. To make a Couette-type shear flow, the medium was sandwiched between parallel disks (the lower stationary culture-disc and the upper rotating disk) with a constant gap. The wall shear stress (1.5 Pa < τ < 2 Pa) on the surface of the lower culture plate was controlled by the rotational speed of the upper disc. Myoblasts (C2C12: mouse myoblast cell line) were used in the test. After cultivation without flow for 24 hours for adhesion of the cells to the lower disk, constant τ was applied to the cells in the incubator for 7 days. The behavior of each cell during shear was tracked by time-lapse images observed by an inverted phase contrast microscope placed in the incubator. Experimental results show that each cell tends to divide after higher activities: deformation and migration. The tendency is remarkable at the shear stress of 1.5 Pa.

Effect of Shear Stress on Granulation in Oxygen Aerobic Upflow Sludge Bed Reactors

1992 ◽  
Vol 26 (3-4) ◽  
pp. 601-605 ◽  
Author(s):  
H.-S. Shin ◽  
K.-H. Lim ◽  
H.-S. Park
Keyword(s):  
Shear Stress ◽  
Morphological Study ◽  
Loading Rate ◽  
Granular Sludge ◽  
Treatment Method ◽  
The Self ◽  
High Rate ◽  
Synthetic Wastewater ◽  
Filamentous Bacteria ◽  
Start Up

Aerobic upflow sludge blanket(AUSB) process is a new biological wastewater treatment method applying the concept of the self-immobilization to activated sludge. Two sets of AUSB system with different mixing velocities of 3 rpm(R1) and 6 rpm(R2) were operated for high-rate treatment of synthetic wastewater. The COD removal efficiency in R2 was higher than R1 at the same loading rate up to 7 kg/m3·day. However, in R1, the sludge bulking was observed at the end of the experiment. The chocolate colored granules were formed about 5 days after the start-up. The morphological study on the granular sludge consortia was made with both scanning electron and optical microscopes. The granules were 0.5-2.5 mm in diameter and mainly consisted of bacteria with pili-like appendages and filamentous bacteria, which were thought to be Sphaerotilus natans and Beggiatoa. In R1, the long multicellular filaments causing bulking were prevalent in the granule, while in R2 overgrowth of filamentous bacteria was prevented with appropriate shear stress resulting in higher MLSS density. Experimental results indicated that granulation could be controlled by physical stress on granular sludge.

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.

Slip velocity over a perforated or patchy surface

2010 ◽  
Vol 643 ◽  
pp. 471-477 ◽  
Author(s):  
C. POZRIKIDIS
Keyword(s):  
Shear Stress ◽  
Shear Flow ◽  
Solid Fraction ◽  
Solid Surface ◽  
Slip Velocity ◽  
Functional Dependence ◽  
Numerical Results ◽  
Surface Geometry ◽  
Universal Law

Shear flow over a solid surface containing perforations or patches of zero shear stress is discussed with a view to evaluating the slip velocity. In both cases, the functional dependence of the slip velocity on the solid fraction of the surface strongly depends on the surface geometry, and a universal law cannot be established. Numerical results for flow over a plate with circular or square perforations or patches of zero shear stress, and flow over a plate consisting of separated square or circular tiles corroborate the assertion.

Responses of human adipose-derived stem cells to interstitial level of extremely low shear flows regarding differentiation, morphology, and proliferation

Lab on a Chip ◽  
2017 ◽  
Vol 17 (12) ◽  
pp. 2115-2124 ◽  
Author(s):  
Sung-Hwan Kim ◽  
Kihoon Ahn ◽  
Joong Yull Park
Keyword(s):  
Stem Cells ◽  
Shear Stress ◽  
Shear Flow ◽  
Shear Flows ◽  
Stress Gradient ◽  
Adipose Derived Stem Cells ◽  
Shear Stress Gradient ◽  
Low Shear

We developed a shear stress-gradient chip, which mimickedin vivointerstitial level of flow. With this system, hASCs' quantitative responses to the interstitial level of shear flow are identified.

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