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混沌或湍流的直接数值模拟是否可能:一个模型非线性的研究

Is a Direct Numerical Simulation of Chaos or Turbulence Possible: A Study of a Model Non-Linearity

Lun-Shin Yao

AI总结:

通过一维Kuramoto-Sivashinsky方程研究Navier-Stokes方程相关的四个数值模拟难题,包括线性稳定性定义困难、非线性相互作用导致的谐波激发、长期解对初始条件的敏感性以及混沌数值解不收敛问题。

摘要:

求解Navier-Stokes方程存在许多微妙的问题。本文在一维Kuramoto-Sivashinsky (KS)方程(一个模型非线性偏微分方程)的框架下,研究了先前在Navier-Stokes方程研究中观察到的几个问题。这种替代方法有望更容易地揭示主要观点,并希望识别与Navier-Stokes方程相关的未解决问题。具体讨论了四个有趣的问题。第一个问题涉及定义时变控制参数的线性稳定和不稳定区域的困难;这相当于Navier-Stokes方程的时变基流。接下来的两个问题是非线性相互作用的后果,包括在恒定或时变控制参数存在下,通过同时激发其谐波或次谐波(傅里叶分量)来演化解,以及长期解对初始条件的敏感性。最后一个问题涉及缺乏收敛的数值混沌解,这是先前未在Navier-Stokes方程中研究过的问题。最后两个问题(非线性相互作用的后果)并不常见。讨论了数值结果揭示的结论和问题。提供了每个问题背后的原因,期望它们能激发进一步研究的兴趣。

英文摘要:

There are many subtle issues associated with solving the Navier-Stokes equations. In this paper, several of these issues, which have been observed previously in research involving the Navier-Stokes equations, are studied within the framework of the one-dimensional Kuramoto-Sivashinsky (KS) equation, a model nonlinear partial-differential equation. This alternative approach is expected to more easily expose major points and hopefully identify open questions that are related to the Navier-Stokes equations. In particular, four interesting issues are discussed. The first is related to the difficulty in defining regions of linear stability and instability for a time-dependent governing parameter; this is equivalent to a time-dependent base flow for the Navier-Stokes equations. The next two issues are consequences of nonlinear interactions. These include the evolution of the solution by exciting its harmonics or sub-harmonics (Fourier components) simultaneously in the presence of a constant or a time-dependent governing parameter; and the sensitivity of the long-time solution to initial conditions. The final issue is concerned with the lack of convergent numerical chaotic solutions, an issue that has not been previously studied for the Navier-Stokes equations. The last two issues, consequences of nonlinear interactions, are not commonly known. Conclusions and questions uncovered by the numerical results are discussed. The reasons behind each issue are provided with the expectation that they will stimulate interest in further study.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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