Experimental study of enhanced flow asymmetry due to viscoelasticity: An assessment of viscoelastic constitutive models

Flow past an asymmetrically confined cylinder of shear-thinning viscoelastic polymer solutions has been experimentally investigated. We show that the flow asymmetry induced by the asymmetric geometry is enhanced at Weissenberg numbers (Wi) above unity; that is, the flow in the nonpreferred pathway decreases significantly, even for small geometric asymmetries. This elastic phenomenon, previously identified in numerical simulations [V. ChandraShekar et al., Phys. Rev. Fluids 10, 023302 (2025)], is now demonstrated experimentally, despite the presence of strong shear-thinning in the test fluids. The experimental results are used to assess four viscoelastic constitutive models that incorporate shear-thinning: White–Metzner, Giesekus, FENE-P, and exponential PTT. Among these, the White–Metzner and Giesekus models reproduce the enhanced flow asymmetry reasonably well, although they deviate from experimental observations at higher degrees of asymmetry. In contrast, the FENE-P and e-PTT models fail to capture the enhancement at constraining values for the extensibility parameters.