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In two-dimensional turbulent flows, negative absolute temperatures can drive irreversible energy conversion from microscopic to macroscopic forms. This study confirms this thermodynamic prediction using a conceptual model and numerical experiments.

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Area of Science:

  • Fluid dynamics
  • Statistical mechanics
  • Thermodynamics

Background:

  • Two-dimensional turbulent flows in geophysical systems are often explained by statistical mechanics.
  • Unusual negative absolute temperatures can occur in 2D systems, challenging conventional thermodynamics.
  • The second law of thermodynamics suggests energy flows from microscopic to macroscopic scales at negative temperatures.

Purpose of the Study:

  • To investigate the one-way energy conversion predicted by negative absolute temperatures in 2D turbulent flows.
  • To explore energy exchange in a 2D flow with a deformable boundary.
  • To verify theoretical predictions using numerical simulations.

Main Methods:

  • A conceptual model of an inviscid, incompressible fluid in a bounded, shape-distorting domain.
  • Analysis based on Kraichnan's grand-canonical ensemble and the Jarzynski equality.
  • Numerical experiments to validate theory and study parameter dependence.

Main Results:

  • The Jarzynski equality is established for domain distortions in finite time.
  • The direction of net energy flow depends on the initial temperature's sign.
  • Energy exchange rates are investigated in relation to system parameters.

Conclusions:

  • The study confirms the possibility of one-way energy conversion in 2D turbulent flows at negative temperatures.
  • Deformable boundaries facilitate energy exchange with the external system.
  • The findings have implications for understanding energy dynamics in geophysical systems.