标题： 密度分层流体振动界面的竞争机制 显示英文标题

标题： Competing Mechanisms at Vibrated Interfaces of Density-Stratified Fluids

摘要： 流体-流体界面不稳定性及其随后的混合现象在自然界和工程领域中无处不在。长期以来，人们认为有两种水动力学不稳定性控制着界面行为：由压力梯度驱动的长波瑞利-泰勒（RT）不稳定性以及共振引起的短波法拉第（Faraday）不稳定性。然而，当这两种机制同时作用时，单独一种不稳定性无法解释这种动力学过程。相反，我们识别出了一种以前未被发现的多模态不稳定性，它源自这两种不稳定性的同时存在。我们展示了振动如何调控RT和法拉第不稳定性之间的转变，这两种不稳定性相互竞争而不是共振增强。初始的瞬态增长可以通过最不稳定Floquet指数的最大指数的指数型模态增长以及其伴随的周期性行为来捕捉。直接数值模拟验证了这些发现，并追踪了界面破裂进入多尺度和非线性区域的过程，在此过程中，生长中的RT模式通过非线性机制抑制了法拉第响应。 显示英文摘要

摘要： Fluid--fluid interfacial instability and subsequent fluid mixing are ubiquitous in nature and engineering. Two hydrodynamic instabilities have long been thought to govern the interface behavior: the pressure gradient-driven long-wavelength Rayleigh--Taylor (RT) instability and resonance-induced short-wavelength Faraday instability. However, neither instability alone can explain the dynamics when both mechanisms act concurrently. Instead, we identify a previously unseen multi-modal instability emerging from their coexistence. We show how vibrations govern transitions between the RT and Faraday instabilities, with the two competing instead of resonantly enhancing each other. The initial transient growth is captured by the exponential modal growth of the most unstable Floquet exponent, along with its accompanying periodic behavior. Direct numerical simulations validate these findings and track interface breakup into the multiscale and nonlinear regimes, in which the growing RT modes are shown to suppress Faraday responses via a nonlinear mechanism.