Paper Number
FI16                         My Program 

Session
Flow-Induced Instabilities and Non-Newtonian Fluids

Title
Pressure drop in a deformable channel distinguishes Newtonian from Boger fluids

Presentation Date and Time
October 20, 2025 (Monday) 5:05

Track / Room
Track 7 / Sweeney Ballroom D

Authors (Click on name to view author profile)

  1. Chun, SungGyu (University of Illinois at Urbana-Champaign, Mechanical Science and Engineering)
  2. Christov, Ivan C. (Purdue University, Mechanical Engineering)
  3. Feng, Jie (University of Illinois at Urbana-Champaign, Mechanical Science and Engineering)

Author and Affiliation Lines (in printed abstract book)
SungGyu Chun1, Ivan C. Christov2 and Jie Feng1
1Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801; 2Mechanical Engineering, Purdue University, West Lafayette, IN 47906

Speaker / Presenter 
Christov, Ivan C.

Keywords
experimental methods; theoretical methods; non-Newtonian fluids; polymer solutions; rheometry

Text of Abstract
We provide a comprehensive experimental-theoretical framework for analyzing the steady flow-induced deformation caused by an incompressible fluid flow in a deformable three-dimensional (3D) channel. We focus on how the flow-induced deformation reduces the pressure drop (for a fixed flow rate) as a function of wall compliance and fluid viscoelasticity. From the theory of Boyko & Christov (J. Non-Newton. Fluid Mech. 313, 104990, 2023), based on the Oldroyd-B model, we calculate the pressure drop of a steady weakly viscoelastic flow (small Deborah number) of a constant-shear-viscosity (i.e., Boger) fluid in a deformable channel. Building on the experimental platform of Chun et al. (Phys. Rev. Fluids 9, 043302, 2024), we measure the pressure drop for a solution of 300 ppm PAA into 10 wt% DI water (Boger fluid), as well as a viscosity-matched solution of 92.1 wt% glycerol into DI water (Newtonian fluid), over a range of Deborah numbers from ~0.01 up to ~0.1, finding good agreement between theory and experiment. Importantly, to ensure a proper comparison and cross-validation between theory and experiment, we perform independent rheological characterization of all fluids used (as well as elastic and geometric quantities). We also conduct experiments in an equivalent rigid channel, showing that both the Boger fluid and a viscosity-matched Newtonian fluid have the same pressure drop. Thus, the pressure drop in a deformable channel distinguishes Newtonian from Boger fluids, offering new ideas for microrheometry.