Interaction of a coherent vortex with plane Couette flow in three-dimensional Yukawa liquids: Formation of turbulent spots
Phys. Rev. Fluids 11, 083301 – Published 10 August, 2026
DOI: https://doi.org/10.1103/d3f4-vx5q
Abstract
In plane Couette flow (PCF), turbulent coherent structures typically appear as turbulent spots or bands. In this study, we investigate the subcritical transition to turbulence in PCF in a three-dimensional Yukawa liquid using first-principles classical 3D molecular dynamics simulations, wherein a monopolar columnar vortex is initialized at the center of the simulation domain to trigger the transition. Some of the features of subcritical turbulence are found to depend on the type of perturbation used in the simulation. In unstratified cases, we observe the emergence of a tripolar vortex structure, whereas in stably stratified conditions, a stable quadrupolar (two stable dipoles) structure forms—a phenomenon rarely reported in prior experiments and simulations. Unlike in supercritical turbulence, the stable background PCF is observed to constrain the coherent vortex structures and prevent them from undergoing rotational motion. The growth of radial kinetic energy is found to be greater in the stratified case compared to the unstratified one. In addition to azimuthal modes 1 and 2, mode 0 emerges as the most energetically dominant in the system. Our results demonstrate that both tripole and quadrupole structures can arise as quasi-coherent modes during a transition to turbulence in PCF.
