Paper Number
MC8
Session
Micro- and Nanofluidics and Confined Flows
Title
Experimental and theoretical studies of cross-stream migration of non-spherical particles in a quadratic flow of viscoelastic fluid
Presentation Date and Time
October 12, 2021 (Tuesday) 4:35
Track / Room
Track 5 / Ballroom 6
Authors
- Tai, Cheng-Wei (Purdue University, Davidson School of Chemical Engineering)
- Wang, Shiyan (Purdue University, Davidson School of Chemical Engineering)
- Narsimhan, Vivek (Purdue University, Davidson School of Chemical Engineering)
Author and Affiliation Lines
Cheng-Wei Tai, Shiyan Wang and Vivek Narsimhan
Davidson School of Chemical Engineering, Purdue University, West Lafayette, IN 47907
Speaker / Presenter
Tai, Cheng-Wei
Keywords
experimental methods; theoretical methods; computational methods; applied rheology; confined flows; microfluidics; nanofluidics; non-Newtonian fluids; polymer solutions; rheology methods; suspensions
Text of Abstract
Particulate suspension in a viscoelastic fluid is common in industrial applications as well as in the fields of microbiology and microrheology. When in a quadratic flow, particles migrate in lateral direction due to the imbalance of normal stress over the particle surface. A detailed understanding on the migration and rotation behavior of non-spherical particles within such system will be vital to developing precise particle manipulation and separation techniques. In the first part of this work, we develop a theory based on the general second-order fluid model under the limit of weak viscoelasticity (Wi « 1) and provide solutions to the polymer force and torque on a non-spherical particle when subject to an arbitrary flow up to quadratic order. Specifically for spheroidal (prolate and oblate) particles, we further investigate the combined effect of fluid normal stress ratio (a = ?_2/?_1), particle geometry and orientation behavior on the overall particle migration trajectory in a quadratic flow. Particles in general gain faster migration speed with the increasing magnitude of a. In terms of particle geometry, the length the particle spans in the shear gradient direction dominates the particle migration speed. In addition, prolate and oblate particle shows distinct orientation behavior, which leads to difference in overall migration speed towards flow center. In the second part of this work, we experimentally verify the theory in a microfluidic system. A suspension of spherical, prolate and oblate polystyrene (PS) particle in 8% polyvinylpyrrolidone (PVP) solution is flowed in a straight glass capillary channel at the rate of vanishing inertia (Re=O(10^(-3))) and weak viscoelasticity (De=O(10^(-2))). We estimate the average particle migration speed by the particle distribution at various distances from the channel inlet. The results show a good agreement with the theory prediction at the corresponding conditions. We also comment on the observation on the particle orientation behavior in the microfluidic system.