Spot formation in three-dimensional Yukawa liquid

Dynamics of a three-dimensional (3D) plane Couette flow (PCF), which subjected to a 3D finite amplitude particle velocity perturbation, is addressed using 3D classical first principles molecular dynamics simulation with screened Coulomb potential or a Yukawa potential as the inter-particle interaction. Such systems are often realized in complex plasmas and charged colloids. Parameters are chosen such that the system is a Yukawa liquid whose kinematic viscosity is a time-dependent function of the particle correlation strength Gamma controlled by shear heating. This feature is found to facilitate a unique quench study of the Reynolds number Re as a function of time for fixed system size and fixed flow speed. For small cross-sectional aspect ratios similar to 20, starting from Re similar to 1211-717, a laminar 3D PCF initial condition is shown to become unstable to localized 3D finite amplitude perturbation for various increasing amplitude strengths, clearly demonstrating the formation of a turbulent spot. This spot is found to spread in time into the otherwise laminar regions, a signature of subcriticality or co-existence of laminar and turbulent regions in PCF in a 3D Yukawa liquid. It is shown unambiguously that the range of interaction of Yukawa potential determines the nature of spot formation and its dynamics. At long range, a qualitative similarity of our results to those found in turbulent spots of PCF in conventional hydrodynamics is discussed. Our findings may have ramifications for a wide range of physical systems that exhibit sub-critical transition to turbulence. Published under an exclusive license by AIP Publishing.

Automated summary

The dynamics of a three-dimensional plane Couette flow subjected to a 3D finite amplitude particle velocity perturbation is studied using classical first principles molecular dynamics simulation with screened Coulomb or Yukawa potential. It is found that the system exhibits unique quench behavior of the Reynolds number as a function of time for fixed system size and flow speed. The formation and spreading of turbulent spots in the otherwise laminar flow are influenced by the range of interaction of the Yukawa potential, with potential implications for systems undergoing sub-critical transition to turbulence.