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arXiv 2109.07398physics.flu-dynmath.AP
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连续对称性在三维欧拉流体方程及相关模型解中的作用

On the role of continuous symmetries in the solution of the 3D Euler fluid equations and related models

Miguel D. Bustamante

摘要:

我们回顾和应用连续对称的方法来寻找三维欧拉流体方程的解决方案在几个感兴趣的情况下,通过建设的运动常数和无穷小对称,而不诉诸Noether定理。我们表明,涡度场是一个对称的流动,所以如果流承认另一个对称,然后可以构建一个李代数的新的对称性。对于稳定的欧拉流,这直接导致(非)贝尔特拉米流的区别:一个例子给出的拓扑结构的空间流形决定是否可以构建额外的对称性。接下来,我们研究了由Giant等人(Physica D,vol.132,1999,pp.497-510)引入的3D Euler流体方程的停滞点型精确解以及由Mulungye等人(J. Fluid Mech.,第771卷,2015年,第468 -502页)。应用对称性的方法,这些模型允许明确集成的领域沿路径,揭示了一个精细的结构爆破的涡度,它的拉伸率,和回标签地图,取决于自由参数的值和初始条件。最后,我们产生明确的爆破指数和前置因子的一般类型的初始条件。

英文摘要:

We review and apply the continuous symmetry approach to find the solution of the 3D Euler fluid equations in several instances of interest, via the construction of constants of motion and infinitesimal symmetries, without recourse to Noether's theorem. We show that the vorticity field is a symmetry of the flow, so if the flow admits another symmetry then a Lie algebra of new symmetries can be constructed. For steady Euler flows this leads directly to the distinction of (non-)Beltrami flows: an example is given where the topology of the spatial manifold determines whether extra symmetries can be constructed. Next, we study the stagnation-point-type exact solution of the 3D Euler fluid equations introduced by Gibbon et al. (Physica D, vol.132, 1999, pp.497-510) along with a one-parameter generalisation of it introduced by Mulungye et al. (J. Fluid Mech., vol.771, 2015, pp.468-502). Applying the symmetry approach to these models allows for the explicit integration of the fields along pathlines, revealing a fine structure of blowup for the vorticity, its stretching rate, and the back-to-labels map, depending on the value of the free parameter and on the initial conditions. Finally, we produce explicit blowup exponents and prefactors for a generic type of initial conditions.

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