Molecular dynamics simulation on shear thinning characteristics of non-Newtonian fluids

Abstract

Non-Newtonian fluids are widely used in microfluidic systems and biomedical fields. In this paper, based on molecular dynamics simulation, taking the system composed of sodium carboxymethyl cellulose molecules and water molecules as the research object, the configuration evolutions of sodium carboxymethyl cellulose solution are simulated under different shear rates. Change of the solution viscosity is characterized by mean square displacement of sodium carboxymethyl cellulose molecules and the relative velocity between water layer and shear boundary. The effect of hydrogen bonding on the viscosity of the solution is analyzed emphatically. The results show that water molecules and solute molecules attract each other to form a more compact hydrogen bond network, which increases the viscosity of the solution; the peak value of the radial distribution function between the hydrogen atoms attached to carbon and the water oxygen atoms decreases when shear action is applied to the solution, and the hydrogen bond between the two atoms is weakened; the mobility of solute molecules increases and the blocking effect of water molecules on the movement of solute molecules weakens under the shear action; at the same time, the shorter the distance to the shear boundary, the closer to the shear velocity the velocity of water molecules is, and with the increase of distance, the velocity of water molecular layer decreases greatly. These results are macroscopically understood as the viscosity of the system decreasing. As the shear rate increases, the shear thinning of the sodium carboxymethyl cellulose solution becomes more significant.

Modified Bentonite As a Dissolve-Extrusion Composite and Its Modification Mechanism

“…The performance of the modified bentonite drilling fluid with combined modifiers was excellent, and the experimental results demonstrated good reproducibility and a stable modification effect. This was mainly attributed to the synergistic effect of ZJ-1 and ZJ-2 in the aqueous solution, achieving a thickening effect through hydrogen bonding with water molecules. , High-molecular-weight modifiers can be adsorbed on the surface of bentonite, forming an adsorbed hydration layer that prevents contact and bonding between the bentonite particles. In addition, the large polymer chains of the modifier can bridge the fine particles of bentonite, forming a network structure throughout the drilling fluid system, thereby improving the performance of the drilling fluid .…”

Synergistic effect of gum arabic and xanthan gum on improving rheological properties of low‐fat mayonnaise with egg white protein microparticle as a fat mimetic

“…As could be seen, regardless of xanthan gum content, all mayonnaise samples showed shear thinning behaviour at 0.1–100 s −1 , resulting from the decomposition of the electrostatic interaction between EWPM and XG and the consequence of a progressive breakdown of aggregates combined with the alignment of xanthan molecules in the shear field (Akapong et al ., 2022). In addition, it could not be excluded that the weakening of hydrogen bonds also played a role in shear thinning during shearing (Yang et al ., 2021). We also could see in the figure that the apparent viscosity of mayonnaise samples increased with the addition of XG.…”