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arXiv 1606.09229nlin.PS
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非凸色散的色散流体力学中的Shock waves

Shock waves in dispersive hydrodynamics with non-convex dispersion

Patrick Sprenger, Mark A. Hoefer

摘要:

由色散正则化的无耗散流体动力学描述了许多物理介质,包括水波、非线性光学和玻色-爱因斯坦凝聚体。在经典的双曲方程理论中,非凸通量导致非经典的解结构,非凸线性色散关系提供了一个有趣的色散流体动力学模拟。在这里,五阶Korteweg-de Vries(KdV)方程,也被称为Kawahara方程,浅水波的经典模型,被证明是一个通用的欧拉流体动力学模型与高阶色散效应。利用渐近方法和数值计算,这项工作分类的阶梯状初始数据的解决方案的长期行为。对于凸色散,结果是色散冲击波(DSW),定性和定量轴承KdV DSW的密切相似。对于非凸色散,观察到三个不同的动态制度。对于小的跳跃,扰动KdV DSW与正极性和方向的产生,伴随着小幅度的辐射从嵌入的孤波前缘,称为辐射DSW或RDSW。对于中度跳跃,观察到一个交叉制度与波向前和向后传播的急剧过渡区。对于超过临界阈值的跳跃,我们观察到一种新类型的DSW,我们称之为平移DSW或TDSW。TDSW由一个行波组成,该行波将后缘处的部分非单调负孤波连接到内部非线性周期波。它的速度是由行波的远场结构决定的,是一个广义的Rankine-Hugoniot跳跃条件。TDSW在前缘由以线性群速度运动的谐波包分解。非经典的TDSW表现出共同的耗散和色散冲击波的功能。

英文摘要:

Dissipationless hydrodynamics regularized by dispersion describe a number of physical media including water waves, nonlinear optics, and Bose-Einstein condensates. As in the classical theory of hyperbolic equations where a non-convex flux leads to non-classical solution structures, a non-convex linear dispersion relation provides an intriguing dispersive hydrodynamic analogue. Here, the fifth order Korteweg-de Vries (KdV) equation, also known as the Kawahara equation, a classical model for shallow water waves, is shown to be a universal model of Eulerian hydrodynamics with higher order dispersive effects. Utilizing asymptotic methods and numerical computations, this work classifies the long-time behavior of solutions for step-like initial data. For convex dispersion, the result is a dispersive shock wave (DSW), qualitatively and quantitatively bearing close resemblance to the KdV DSW. For non-convex dispersion, three distinct dynamic regimes are observed. For small jumps, a perturbed KdV DSW with positive polarity and orientation is generated, accompanied by small amplitude radiation from an embedded solitary wave leading edge, termed a radiating DSW or RDSW. For moderate jumps, a crossover regime is observed with waves propagating forward and backward from the sharp transition region. For jumps exceeding a critical threshold, a new type of DSW is observed we term a translating DSW or TDSW. The TDSW consists of a traveling wave that connects a partial, non-monotonic, negative solitary wave at the trailing edge to an interior nonlinear periodic wave. Its speed, a generalized Rankine-Hugoniot jump condition, is determined by the far-field structure of the traveling wave. The TDSW is resolved at the leading edge by a harmonic wavepacket moving with the linear group velocity. The non-classical TDSW exhibits features common to both dissipative and dispersive shock waves.

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