Acta mathematica scientia,Series A ›› 2020, Vol. 40 ›› Issue (2): 315-327.

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Dynamical Mechanism and Energy Evolution of a Five-Modes System of the Navier-Stokes Equations For a Two-Dimensional Incompressible Fluid on a Torus

Heyuan Wang1,2()   

  1. 1 College of Mathematics and Systematics Sciences, Shenyang Normal University, Shenyang 110034
    2 College of Sciences, Liaoning University of Technology, Liaoning Jin'zhou 121001
  • Received:2018-04-11 Online:2020-04-26 Published:2020-05-21
  • Supported by:
    the NSFC(11572146);the Doctor Science Foundation of Shenyang Normal University(054-91900302009)

Abstract:

In this paper we study dynamical mechanism and energy evolution of a five-modes system of the Navier-Stokes equations for a two-dimensional incompressible fluid on a torus. The five-modes system is transformed into Kolmogorov type system, which is decomposed into three types of torques:inertial torque, dissipation and external torque. Combining different torques, key factors of chaos generation and the physical meaning of the five-modes system are studied. The evolution of energy is investigated, the relationship between the energies and the Reynolds number is discussed. We conclude that the combination of the three torques is necessary conditions to produce chaos, and only when the dissipative torques match the driving torques (external torque) the system can produce chaos. While any combination of two types of torques cannot produce chaos. The external torque supply the energy for the system, and that leads to bifurcation and chaos. The Casimir function is introduced to analyze the system dynamics, and its derivation is chosen to formulate energy evolution. The bound of chaotic attractor is obtained by the Casimir function and Lagrange multiplier. We find that the Casimir function reflects the energy evolution and the distance between the orbit and the equilibria.

Key words: Dynamical Mechanism, Kolmogorov system, Chaos

CLC Number: 

  • O175.1
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