No CrossRef data available.
Article contents
Small-scale shear layers in isotropic turbulence of viscoelastic fluids
Published online by Cambridge University Press: 26 February 2025
Abstract
Small-scale shear layers arising from the turbulent motion of viscoelastic fluids are investigated through direct numerical simulations of statistically steady, homogeneous isotropic turbulence in a fluid described by the FENE-P model. These shear layers are identified via a triple decomposition of the velocity gradient tensor. The viscoelastic effects are examined through the Weissenberg number ($Wi$), representing the ratio of the longest polymer relaxation time scale to the Kolmogorov time scale. The mean flow around these shear layers is analysed within a local reference frame that characterises shear orientation. In both Newtonian and viscoelastic turbulence, shear layers appear in a straining flow, featuring stretching in the shear vorticity direction and compression in the layer normal direction. Polymer stresses are markedly influenced by the shear and strain, which enhance kinetic energy dissipation due to the polymers. The shear layers in viscoelastic turbulence exhibit a high aspect ratio, undergoing significant characteristic changes once
$Wi$ exceeds approximately 2. As
$Wi$ increases, the extensive strain weakens, diminishing vortex stretching. This change coincides with an imbalance between extension and compression in the straining flow. In the shear layer, the interaction between vorticity and polymer stress causes the destruction and production of enstrophy at low and high
$Wi$ values, respectively. Enstrophy production at high
$Wi$ is induced by normal polymer stress oriented along the shear flow, associated with the diminished extensive strain. The
$Wi$-dependent behaviour of these shear layers aligns with the overall flow characteristics, underscoring their pivotal roles in vorticity dynamics and kinetic energy dissipation in viscoelastic turbulence.
JFM classification
- Type
- JFM Papers
- Information
- Copyright
- © The Author(s), 2025. Published by Cambridge University Press
References
