The thermodynamic entropy of the Euler current remains constant according to the rules of thermodynamics. prof. Mahendra Verma and research scientist Soumyadeep Chatterjee of the Department of Physics, IIT Kanpur introduced “hydrodynamic entropy” as a measure of order in a multiscale, non-equilibrium system such as hydrodynamic and astrophysical systems and applied it to turbulence.

They found that 2D Euler flow, or flow without viscosity, progresses from disorder to order. Analytical arguments and precise numerical simulations were used in this study, which provides insightful information that can improve how scientists approach crucial fundamental topics, such as the evolution from order to disorder, the second law of thermodynamics, and thermalization, the process by which physical processes reach thermal equilibrium. to achieve. .

The two-dimensional Euler flow changes from order to disorder and the system is out of equilibrium due to an intriguing energy exchange between the flow structures that violates the precise energy balance. The non-equilibrium behavior of 2D Euler turbulence is caused by a reverse cascade of energy.

Using hydrodynamic entropy for Euler turbulence, scientists have shown that the hydrodynamic entropy of 2D Euler flow decreases with time while approaching the asymptotic state. The duo has also discovered that the final state of the current depends critically on the initial state.

The findings illustrate that the isolated dynamical system can evolve from disorder to order on a macroscopic scale and that one should be careful about general claims about the “evolution from order to disorder” in any system. Based on their findings, Prof. Verma and Mr. Chatterjee that a similar evolution can occur in self-attracting systems.

According to scientists, hydrodynamic entropy can be useful for quantifying order in biological, hydrodynamic, astrophysical, ecological and economic systems.

Magazine reference:

  1. Mahendra K. Verma and Soumyadeep Chatterjee. Hydrodynamic entropy and order origination in two-dimensional Euler turbulence. Physical assessment fluids. Volume 7. November 2022. Article #: 114608. DOI: 10.1103/PhysRevFluids.7.114608