2022/08/28 by Arjun D. Sharma, Sharma, Arjun, Donald L. Koch +1 · 1 citation
Chemical Engineering · Medicine · #Blood properties and coagulation #FOS: Physical sciences #Fluid Dynamics (physics.flu-dyn) #Rheology and Fluid Dynamics Studies #Soft Condensed Matter (cond-mat.soft)
paper · pdf · doi:10.48550/arxiv.2208.13110
openalex publication_date 2022/08/28 · openalex created_date 2022/08/31 · openalex updated_date 2026/07/28
We investigate the steady-state extensional rheology of a dilute suspension of spherical particles in a dilute polymer solution. For a particle-free polymeric fluid, in addition to the solvent viscosity, the extensional viscosity due to the polymers, μpoly, contributes to the total non-dimensionalized extensional viscosity 1+μpoly. When a small volume fraction, ϕ, of spheres is added to a polymeric fluid, the stress is altered by the Einstein viscosity of 2.5ϕ and two additional stress contributions: the interaction stresslet and the particle-induced polymer stress (PIPS). The net interaction stress is positive at lower Deborah numbers (product of extension rate and polymer relaxation time), De\lesssim0.5, and negative at large De. Relative to undisturbed flow, the presence of spheres in uniaxial extensional flow creates larger and smaller local stretching regions. Below the coil-stretch transition (De<0.5), the polymers far from the particles are in a coiled state, and a wake of stretched polymers forms downstream of the particle as they are stretched by the large stretching regions around the particle. This leads to a positive interaction stresslet (surface) and the PIPS (stretched wake). Beyond the coil-stretch transition, polymers far from the particle are highly stretched, but they collapse closer to the coiled state as they arrive at the low-stretching regions near the particle surface. Therefore, a negative PIPS results from the regions of collapsed polymers. When De\gtrsim0.6, the changes in extensional viscosity from the interaction stresslet and the PIPS are ϕμpoly and approximately -1.85ϕμpoly, respectively. At large De, the polymer extensional viscosity, μpoly, is large. Therefore, adding particles reduces the extensional viscosity of the suspension ((2.5-0.85μpoly)ϕ<0).