Viscoelastic 'narwhals': two-dimensional coherent states in pressure-driven channel flow at vanishing inertia*

In this talk we present the first coherent state in purely elastic parallel shear flows [1]. We perform direct numerical simulations of a model viscoelastic fluid driven by an applied pressure gradient through a two-dimensional channel. While the flow is linearly stable, we find that a sufficiently strong finite-amplitude perturbation leads to the appearance of sub-critical travelling-wave solutions, in line with previous theoretical [2] and experimental [3] studies. We refer to these solutions as ‘narwhals’ for their visual resemblance. We explore the region of their existence and discuss how ‘narwhals’ are sustained.

[1] A. Morozov, Phys. Rev. Lett. 129, 017801 (2022)

[2] A. Morozov and W. van Saarloos, J. Stat. Phys. 175, 554 (2019)

[3] L. Pan, A. Morozov, C. Wagner, and P. E. Arratia, Phys. Rev. Lett. 110, 174502 (2013)