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arXiv 2008.08853math.AP
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Boussinesq系统的松弛及其对Rayleigh-Taylor不稳定性的应用

Relaxation of the Boussinesq system and applications to the Rayleigh-Taylor instability

Björn Gebhard, József J. Kolumbán

摘要:

考虑了两种不可压缩流体在重力作用下的演化问题,即由无粘Boussinesq方程描述的具有均匀密度$ρ_-<ρ_+$的不可压缩流体,并给出了相应的微分包含的显式松弛.松弛子解的存在性使得人们可以得出结论,存在原始Boussinesq系统的混合解。作为一个具体的应用程序,我们调查子解决方案所产生的经典Rayleigh-Taylor初始配置,其中两种流体是由一个水平的接口与较重的流体被上的轻。结果表明,在所有自相似子解中,最大初始能量耗散准则选择线性密度分布和二次增长的混合区。这样选择的子解可以以一种容许的方式扩展到任何时候都存在。我们提供了两种可能的扩展不同的时间限制。第一种对应于两种流体的完全混合,第二种对应于较轻流体在较重流体之上的完全分离。在两种极限状态下都没有运动。

英文摘要:

We consider the evolution of two incompressible fluids with homogeneous densities $ρ_-<ρ_+$ subject to gravity described by the inviscid Boussinesq equations and provide the explicit relaxation of the associated differential inclusion. The existence of a subsolution to the relaxation allows one to conclude the existence of turbulently mixing solutions to the original Boussinesq system. As a specific application we investigate subsolutions emanating from the classical Rayleigh-Taylor initial configuration where the two fluids are separated by a horizontal interface with the heavier fluid being on top of the lighter. It turns out that among all self-similar subsolutions the criterion of maximal initial energy dissipation selects a linear density profile and a quadratic growth of the mixing zone. The subsolution selected this way can be extended in an admissible way to exist for all times. We provide two possible extensions with different long-time limits. The first one corresponds to a total mixture of the two fluids, the second corresponds to a full separation with the lighter fluid on top of the heavier. There is no motion in either of the limit states.

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