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Acceleration-based classification and evolution of fluid flow structures in two-dimensional turbulence.

Tristan Faber1, J C Vassilicos

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|September 28, 2010
PubMed
Summary
This summary is machine-generated.

Zero acceleration points (ZAPs) in turbulence are classified using the acceleration gradient tensor. Anti-ZAPs mediate between vortical and straining ZAPs, influencing flow structures and lifetimes.

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Area of Science:

  • Fluid Dynamics
  • Turbulence Theory
  • Computational Physics

Background:

  • Turbulence research often focuses on velocity and vorticity.
  • Zero acceleration points (ZAPs) represent critical locations within turbulent flows.
  • Understanding ZAPs is crucial for characterizing turbulent structures and dynamics.

Purpose of the Study:

  • To classify Zero Acceleration Points (ZAPs) using the invariants of the acceleration gradient tensor.
  • To investigate the flow structures and statistical properties associated with different ZAP types.
  • To analyze the dynamics and lifetimes of ZAPs in homogeneous isotropic turbulence.

Main Methods:

  • Direct numerical simulation of 2D, stationary, homogeneous, isotropic turbulence.
  • Analysis of the acceleration gradient tensor and its invariants at ZAPs.
  • Statistical analysis of ZAP populations, types, and interactions.

Main Results:

  • A classification of ZAPs based on the invariants of the acceleration gradient tensor (∇a) was established.
  • Approximately 50% of ZAPs were identified as anti-ZAPs (det(∇a)<0), with equal numbers of vortical and straining ZAPs (det(∇a)>0).
  • Vortical and straining ZAPs are generally advected by the local fluid velocity, unlike anti-ZAPs.

Conclusions:

  • The classification provides a robust framework for understanding ZAP behavior in turbulent flows.
  • Anti-ZAPs play a mediating role between vortical and straining regions, influencing flow structure organization.
  • ZAP lifetimes appear to scale with the smallest eddy turnover time, with potential for longer survival.