论文标题
Leidenfrost流：不稳定性和对称性破坏
Leidenfrost flows: instabilities and symmetry breakings
论文作者
论文摘要
最近发现Leidenfrost滴剂具有强大的动力学。在本研究中，我们在实验和理论上都在研究液冻水水滴内部的{FORWS结构和稳定性}蒸发时，从大水坑开始。正如红外映射所揭示的那样，下降基底通常比其顶点更温暖，通常10 $^{\ circ} $ c，这很可能会触发散装热量流量和marangoni表面流量。示踪剂颗粒揭示了随着滴蒸发而经历连续的对称性断裂的强烈流动。我们仅使用一个可调节的参数，研究了由热育性和有效热毛细血管表面应力引起的非构造，准静态的悬浮液的线性稳定性。由drop radius $ r $参数参数的名义轴对称热感染流的稳定性分析产生了最不稳定的，{因此，占主导地位的方位角模式（wavenumber $ m $）。我们的理论可以很好地预测模式过渡的半径$ r $，并从$ m = 3 $，$ m = 2 $，降低到$ m = 1 $（最终导致推进模式）的降低，随着降落的尺寸缩小}，我们的Radii $ r $。这里没有考虑到逃逸蒸气的效果，这可能会进一步破坏内部流动的稳定，并将夫妇融入液体/蒸气界面，从而引起运动Bouillant等。 （2018）[8]和Brandao等。 （2020）[9]。
Leidenfrost drops were recently found to host strong dynamics. In the present study, we investigate both experimentally and theoretically the {flows structures and stability} inside a Leidenfrost water drop as it evaporates, starting with a large puddle. As revealed by infrared mapping, the drop base is warmer than its apex by typically 10$^{\circ}$C, which is likely to trigger bulk thermobuoyant flows and Marangoni surface flows. Tracer particles unveil complex and strong flows that undergo successive symmetry breakings as the drop evaporates. We investigate the linear stability of the baseflows in a non-deformable, quasi-static, levitating drop induced by thermobuoyancy and effective thermocapillary surface stress, using only one adjustable parameter. The stability analysis of nominally axisymmetric thermoconvective flows, parametrized by the drop radius $R$, yields the most unstable, {thus, dominant, azimuthal modes (of wavenumber $m$). Our theory predicts well the radii $R$ for the mode transitions and cascade with decreasing wavenumbers from $m=3$, $m=2$, down to $m=1$ (the eventual rolling mode that entails propulsion) as the drop shrinks in size}. The effect of the escaping vapor is not taken into account here, which may further destabilize the inner flow and couple to the liquid/vapor interface to give rise to motion Bouillant et al. (2018) [8] and Brandao et al. (2020) [9].
