Using Computational Modelling to Study Extensional Rheometry Tests for Inelastic Fluids

The present work focuses on the extensional rheometry test, performed with the Sentmanat extensional rheometer (SER) device, and its main objectives are: (i) to establish the modelling requirements, such as the geometry of the computational domain, initial and boundary conditions, appropriate case setup, and (ii) to investigate the effect of self-induced errors, namely on the sample dimensions and test temperature, on the extensional viscosity obtained through the extensional rheometry tests. The definition of the modelling setup also comprised the selection of the appropriate mesh refinement level to model the process and the conclusion that gravity can be neglected without affecting the numerical predictions. The subsequent study allowed us to conclude that the errors on the sample dimensions have similar effects, originating differences on the extensional viscosity proportional to the induced variations. On the other hand, errors of a similar order of magnitude on the test temperature promote a significant difference in the predicted extensional viscosity.

A microfluidic approach to studying the injection flow of concentrated albumin solutions

Subcutaneous injection by means of prefilled syringes allows patients to self-administrate high-concentration (100 g/L or more) protein-based drugs. Although the shear flow of concentrated globulins or monoclonal antibodies has been intensively studied and related to the injection force proper of SC processes, very small attention has been paid to the extensional behavior of this category of complex fluids. This work focuses on the flow of concentrated bovine serum albumin (BSA) solutions through a microfluidic “syringe-on-chip” contraction device which shares some similarities with the geometry of syringes used in SC self-injection. By comparing the velocity and pressure measurements in complex flow with rheometric shear measurements obtained by means of the “Rheo-chip” device, it is shown that the extensional viscosity plays an important role in the injection process of protinaceous drugs. Article Highlights A microfluidic “syringe on chip” device mimicking the injection flow of protinaceous drugs has been developed. The velocity field of concentrated BSA solutions through the “syringe on chip” is Newtonian-like. The extensional viscosity of concentrated protein solutions should also be considered when computing injection forces through needles.

Influence of Tack Speed on The Rheological Properties of Mortar in Fresh State

In the present work, the squeeze flow techniques were used to investigate the influence of tack speed to the rheological properties of mortar in fresh sate, including yield stress and extensional viscosity.Tested samples were prepared under similar conditions of room temperature and atmospheric pressure. Compositions of mortars were tested at two different squeezing rates (20 and 200 mm/s) 15 min after mixing. Results indicate that mortar’s yield stress increases with the increasing of the pulling speed. This increase is evident at low tensile speeds. At high speed of tack, this increase is not obvious, especially in case of high squeeze speed of 200 mm/s. It can be concluded that the optima speed for removing the mortar and the upper surface is lower than 20 mm/s. The extensional viscosity of fresh mortars significantly decrease as the tack speed increases. Elongational viscosity values decreased as a result of gap increasing. The increase of the gap during tack experiment stimulates different units (grains getting far apart to each other) causing the observed decrease of the mortars' elongational viscosity

Extensional Effects during Viscoelastic Polymer Flooding: Understanding Unresolved Challenges

Summary Several studies have tried to relate polymers’ enhanced oil recovery (EOR) potential to their viscoelastic characteristics such as onset, rheo thickening, extensional viscosity, and Deborah number (De). Contradictions prevail when it comes to reduction in residual oil saturation (Sor) during polymer flooding and the role of extensional properties. De calculated using the oscillatory relaxation time fails to explain the different pressure profiles exhibited by the viscous and viscoelastic polymers. Extensional viscosity has been ignored in many studies as the reason for additional Sor reduction based on the core-scale apparent viscosity and core-scale capillary number (Nc). In recent studies, a significant oil mobilization was shown by the viscoelastic polymers even before the critical Nc, which indicates that the capillary theory breaks out under specific conditions during polymer flooding. Moreover, the additional residual oil recovery caused by the high-salinity polymer solutions cannot be explained by the oscillatory De. In this paper, we compile and examine many such unresolved challenges from various literature with rheological and petrophysical insights. The uniaxial bulk extensional rheology is performed on the relevant polymers using a capillary breakup extensional rheometer to measure the extensional relaxation time, maximum extensional viscosity at the critical De, and strain hardening index. A detailed analysis signifies the role of extensional rheology on the viscoelastic onset, rheo thickening, and Sor reduction even under varying salinity conditions. The results also highlight the advantages of extensional rheology over oscillatory rheology and validate the capillary theory using modified capillary number.

Deterministic Extensional Viscosity and Cracking Index of Polypropylene-Modified-Asphalt Binder

The extensional viscosity and cracking prospectus of polypropylene modified asphalt cement (PPMAC) was explored. Forty/fifty penetration class asphalt cement with fivecontents of polypropylene polymer were chosen. Conventional traits such as: Standard penetration, standard softening point, ductility, utter viscosity, elasticity moduli, penetration prospectus, ageing, cracking prospectus, homogeneity, and extensional viscosity were performed on PPMAC. The PPMAC shows better viscosity, elasticity, enduringness and lower cracking properties at cold regions

Microfluidic rheology of methylcellulose solutions in hyperbolic contractions and the effect of salt in shear and extensional flows

The addition of NaCl to methylcellulose solutions increases the extensional viscosity, which can be measured quantitatively using hyperbolic microfluidic contractions. Fluid stresses during flow can be visualized via birefringence.

The role of extensional rheology in the oral phase of swallowing: an in vitro study

In vitro swallowing experiments suggest that thin, viscoelastic liquids with strong apparent extensional viscosity lead to fast transit, lower oral residues and a compact bolus leaving the oral cavity.