Coherent Structures in Elasto-Inertial Taylor Couette Flows

  • Boulafentis, Theofilos (University College London)
  • Lacassagne, Tom (IMT Nord Europe)
  • Cagney, Neil (Queen Mary University of London)
  • Balabani, Stavroula (University College London)

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Taylor-Couette (TC) flow, the flow between two concentric cylinders with one or both of them rotating, has been studied extensively in the case of Newtonian fluids or in the case of viscoelastic instabilities. In the case of fluids of significant elasticity and negligible shear-thinning, known as Boger fluids, an abundance of transitions to elasto-inertial turbulence (EIT) have been reported: vortex merging and splitting transition (MST) (Lacassagne et al., 2020), flame-pattern (FP) for fluids of higher elasticity (Latrache and Mutabazi, 2021) or the hysteretic, solitary vortex pairs of diwhirls (DW) (Groisman and Steinberg, 1998). However, despite the extensive numerical work on EIT of TC flows (Song et al., 2021), the experimental work is limited in number and visualization experiments are used in most cases. We report Particle Image Velocimetry (PIV) measurements of TC flows of Boger fluids. We examine a range of fluid elasticities (El = 0.057 − 0.341), in order to resolve the structural properties of the elasto-inertial transitions and turbulent flow states. The experimental data highlight the importance of vortex pairs as structural elements of viscoelastic flows, which based on their stability and interaction lead to different flow states, previously reported in the literature.