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arXiv 1707.09314physics.flu-dyn
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带Dirichlet边界条件的受限不可压纳维-斯托克斯方程的精确解

Exact Solutions for Restricted Incompressible Navier--Stokes Equations with Dirichlet Boundary Conditions

Manuel García-Casado

摘要:

本文阐述了如何得到一个对所有按纳维-斯托克斯方程发展的自由发散速度场都必须成立的关系式。然而,检查这种关系的违反需要巨大的计算工作量。为了解决这个问题,提出了一个附加的antennas自由发散Navier-Stokes场。这使得六个自由度可被调节。当它们被充分调谐时,就有可能找到$\mathbb{R}^3$和$t\in[t_0,\infty)$体积的速度场的有限$L^2$范数。特别地,当场分量$u_i$是保持Dirichlet边界条件的$\mathbb{R}^3\times[t_0,\infty)$上的类$C^3$函数时,系统的动能是有界的。这一附加关系使我们得出无滑移边界条件下的纳维-斯托克斯方程没有唯一解的结论。此外,在给定外力作用下,动能可以精确地计算为时间的函数。

英文摘要:

This paper exposes how to obtain a relation that have to be hold for all free--divergence velocity fields that evolve according to Navier--Stokes equations. However, checking the violation of this relation requires a huge computational effort. To circumvent this problem it is proposed an additional antsatz to free-divergent Navier--Stokes fields. This makes available six degrees of freedom which can be tuned. When they are tuned adequately, it is possible to find finite $L^2$ norms of the velocity field for volumes of $\mathbb{R}^3$ and for $t\in[t_0,\infty)$. In particular, the kinetic energy of the system is bounded when the field components $u_i$ are class $C^3$ functions on $\mathbb{R}^3\times[t_0,\infty)$ that hold Dirichlet boundary conditions. This additional relation lets us conclude that Navier--Stokes equations with no-slip boundary conditions have not unique solution. Moreover, under a given external force the kinetic energy can be computed exactly as a funtion of time.

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