Phenomena such as shear thinning and thickening, occurring when complex materials are exposed to external forces, are generally believed to be closely connected to changes in the microstructure. Here, we establish a direct and quantitative relation between shear thinning in a colloidal crystal and the surface area of the locally melted region by dragging a probe particle through the crystal usi...

In the pleural space, sliding between the lung and chest wall induces shear stress that could damage the delicate mesothelial cells covering the tissue surfaces. Normally, the pleural space, which is filled with fluid, is able to sustain continuous shear loading throughout its lifetime. To understand the mechanisms in preventing frictional damage on mesothelial tissue, we conducted experiments ...

We investigate a variety of different polymer solutions in shear and elongational flow. The shear flow is created in the cone-plate-geometry of a commercial rheometer. We use capillary thinning of a filament that is formed by a polymer solution in the Capillary Breakup Extensional Rheometer (CaBER) as an elongational flow. We compare the relaxation time and the elongational viscosity measured i...

We report the design of a bottle-brush polymer whose architecture closely mimics the lubricating protein lubricin. Interaction forces, assessed using a Surface Forces Apparatus (SFA), between two mica surfaces fully covered by the polymer demonstrate that the polymer adopts a loop conformation giving rise to a weak and long-range repulsive interaction force between the surfaces. Under high comp...

flow field and heat transfer of a nanofluid, whose non-newtonian behavior has been demonstrated in the laboratory, in a square enclosure have been numerically modeled and investigated. to estimate the viscosity of nanofluid, experimental data of hong and kim, 2012 have been used, and a new model has been proposed. finally, the obtained results have been compared to those of newtonian behavior. ...

We observe a new type of behavior in a shear-thinning yield stress fluid: freestanding convection rolls driven by vertical oscillation. The convection occurs without the constraint of container boundaries, yet the diameter of the rolls is spontaneously selected for a wide range of parameters. The transition to the convecting state occurs without hysteresis when the amplitude of the plate accele...

this paper presents a numerical simulation of developing flow and heat transfer of a viscoelastic fluid in a rectangular duct. in fully developed flow of a viscoelastic fluid in a non-circular duct, secondary flows normal to the flow direction are expected to enhance the rate of heat and mass transfer. on the other hand, properties such as viscosity, thermal conductivity, specific heat and rela...

Multilayer sol-gel optical high reflectors with greater than 99% reflection have been prepared on substrates up to 20 cm in diameter by spin coating silica/alumina colloidal suspensions. These coatings are radially nonuniform, owing to the extensive shear-thinning rheology of the high-index alumina suspension. To a large degree the film thickness nonuniformity can be compensated for by the refl...

The paper is focused to the experimental investigations of weakly elastic viscous flows in complex geometries, with application in biofluid mechanics. The test samples, polyacrylamide solutions in water characterized by very low relaxation times ( λ < 0.01 s), have similar shear rheology with blood at medium and high shear rates. The flow configuration is a special designed “T” branch Hele – Sh...

We characterize the transient response of semi-dilute wormlike micellar solutions under an imposed steady shear flow in a cone-plate geometry. By combining conventional rheometry with 2-D Particle Image Velocimetry (PIV), we can simultaneously couple the temporal stress response with time-resolved velocimetric measurements. By imposing a well defined shear history protocol, consisting of a step...