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arXiv physics/0509087physics.flu-dyn
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粘性浅层流体中Faraday波不稳定性的强迫函数控制

Forcing function control of Faraday wave instabilities in viscous shallow fluids

Cristian Huepe, Yu Ding, Paul Umbanhowar, Mary Silber

摘要:

我们调查的线性表面波不稳定性的浅粘性流体层和形状的周期性,参数强迫函数(描述的垂直加速度的流体容器),激发他们之间的关系。我们发现,数值的共振舌的包络只能发展多个最小值时,强制功能有两个以上的本地极值每个周期。有了这个见解,我们构建了一个多频强迫函数,在发病时产生一个非平凡的谐波不稳定性,这是不同的次谐波响应其任何频率分量。我们测量相应的表面图案的实验和验证,在强迫波形的小变化会导致过渡,通过一个双临界点,从预测的谐波短波长图案到一个更大的标准次谐波图案。使用配方有效的润滑制度(薄粘性流体层)和WKB方法找到其解析解,我们探索的强迫函数的形状和共振舌结构之间的观察到的关系的起源。特别是,我们表明,平方和三角形的强制功能,这些舌头的信封只有一个最小值,在通常的正弦曲线的情况下。

英文摘要:

We investigate the relationship between the linear surface wave instabilities of a shallow viscous fluid layer and the shape of the periodic, parametric-forcing function (describing the vertical acceleration of the fluid container) that excites them. We find numerically that the envelope of the resonance tongues can only develop multiple minima when the forcing function has more than two local extrema per cycle. With this insight, we construct a multi-frequency forcing function that generates at onset a non-trivial harmonic instability which is distinct from a subharmonic response to any of its frequency components. We measure the corresponding surface patterns experimentally and verify that small changes in the forcing waveform cause a transition, through a bicritical point, from the predicted harmonic short-wavelength pattern to a much larger standard subharmonic pattern. Using a formulation valid in the lubrication regime (thin viscous fluid layer) and a WKB method to find its analytic solutions, we explore the origin of the observed relation between the forcing function shape and the resonance tongue structure. In particular, we show that for square and triangular forcing functions the envelope of these tongues has only one minimum, as in the usual sinusoidal case.

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