Propelled microparticle hydrodynamics model developed for non-Newtonian fluids
Propelled microparticle hydrodynamics model developed for non-Newtonian fluids lead image
Many systems in nature involve the locomotion of microscale objects in non-Newtonian fluids, with examples including E. coli in the digestive system, or bacteria in blood. Conventionally, these systems have been approximated with Newtonian fluids, where the viscosity is independent of the shear force from fluid motion or flow, simplifying the mathematical formulation. However, more sophisticated approaches are needed for better precision in natural systems, where fluid behavior deviates to be more non-Newtonian.
New work provides numerical calculations that describe the effects of small, propelled objects in a typical class of fluids called power-law fluids. The model examines shear-thinning, shear-thickening, and typical Newtonian (shear-viscosity independent) fluids that are each examined to gain qualitative comparisons of the effect of fluid type on the squirmer hydrodynamics.
The model assumes a spherical (or circular) squirmer and solves the momentum and continuity differential equations, which include the squirmer propulsion and fluid forces, for a specimen traveling through a cylindrical boundary. As the squirmer begins to move, a velocity flow field is generated in the fluid, changing the viscosity of the fluid and altering the squirmer velocity.
The authors performed a parametric study to determine the squirmer behavior, and velocity contours were generated for various conditions. The interactions between the squirmer propulsion and the fluid shear force against its motion were important factors for each of the fluid types, leading to behavior that was distinct from Newtonian fluids. Verifying the development against previous works for specific conditions gave additional credence to the results and more specific conditions for future works.
Source: “The hydrodynamic behavior of a squirmer swimming in power-law fluid,” by Zhenyu Ouyang, Jianzhong Lin, and Xiaoke Ku, Physics Of Fluids (2018). The article can be accessed at https://doi.org/10.1063/1.5045701 .
