Paper Number
IN4
Session
Flow-induced Instabilities in Non-Newtonian Fluids
Title
Symmetry breaking in the problem of bubble rising through viscoelastic materials
Presentation Date and Time
October 11, 2022 (Tuesday) 4:45
Track / Room
Track 5 / Sheraton 2
Authors
- Moschopoulos, Pantelis (University of Patras, Department of Chemical Engineering)
- Dimakopoulos, Yiannis (University of Patras, Department of Chemical Engineering)
- Tsamopoulos, John (University of Patras, Department of Chemical Engineering)
Author and Affiliation Lines
Pantelis Moschopoulos, Yiannis Dimakopoulos and John Tsamopoulos
Department of Chemical Engineering, University of Patras, Patras, Achaia 26225, Greece
Speaker / Presenter
Tsamopoulos, John
Keywords
computational methods; flow-induced instabilities; polymer solutions
Text of Abstract
The peculiar dynamics of rising bubbles in viscoelastic solutions has stirred a lot of interest in the scientific community. The three main phenomena that have been identified over the ongoing 60 years of research are: (a) the velocity jump discontinuity [1,2], (b) the negative wake structure [3], and (c) the knife-edge bubble shape [3]. Recent numerical simulations [4] captured accurately the first two effects. However, the notorious knife edge shape has not been reproduced. To this end, we undertake a novel, fully 3D computational study to examine the buoyancy-driven rise of a bubble in a viscoelastic solution because we are interested in finding solutions that do not exhibit azimuthal symmetry. The exponential Phan-Thien & Tanner constitutive equation [5] is used to model the rheological behavior of the material. The governing momentum and mass balances are solved numerically using the newly developed finite element method for free surfaces by Varchanis et al. [6], namely PEGAFEM-V. Also, we impose the center-of-bubble volume to remain at the origin of the coordinate system, and we use an elliptic grid generation scheme [7] to track the bubble-fluid interface. By varying the rheological properties of the material, like the relaxation time, as well as the volume of the bubbles, we simulated cases where axial symmetry breaks down. Based on our results, we try to elucidate the effect of elasticity in these unique results, and the physical mechanism that leads to the knife-edge shape. [1] Astarita & Apuzzo, AIChE J. 11, 815 (1965) [2] Pilz & Brenn, JNNFM 145, 215 (2007) [3] Hassager, Nature, 279, 402 (1979) [4] Fraggedakis, Pavlidis, Dimakopoulos & Tsamopoulos, JFM, 789, 310 (2016). [5] Phan-Thien, JoR 22, (1978); Phan-Tien & Tanner, JNNFM, 2, (1977) [6] Varchanis, Syrakos, Dimakopoulos & Tsamopoulos, JNNFM, 284, 104365 (2020) [7] Dimakopoulos & Tsamopoulos, J. Comp. Phys., 192(2), 494 (2003)