Leidenfrost drops have demonstrated promising applications in, for example, drag reduction. However, large Leidenfrost drops may be unstable when their diameters exceed a critical value, leading to less control of such drops in their applications. In this work, through theoretical and experimental investigations, the authors explore the instability of a Leidenfrost drop in a circular configuration, as well as the suppression of this instability using a small rod. There are four findings. First, the diameter of the largest inscribed cylinder inside a rod–container configuration is the critical dimension for determining Leidenfrost instability. Second, in the cases of water and isopropyl alcohol, the threshold value of this diameter is 8.3λ ± 0.3λ, where λ is the capillary length of the liquid. Third, due to the specific interface profile between the liquid drop and the surrounding vapor layer, the threshold diameter of a circular container for instability to occur is slightly larger than its counterpart in the corresponding Rayleigh–Taylor instability problem. Fourth and finally, placing a rod inside a circular container reduces the size of the largest inscribed cylinder in the container. If the diameter of this inscribed cylinder is below the threshold value, the instability inside the container is suppressed.

中文翻译：

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圆形容器中的莱顿弗罗斯特不稳定性及其使用棒的抑制

莱顿弗罗斯特水滴已在减阻等领域展现出广阔的应用前景。然而，当大的莱顿弗罗斯特液滴的直径超过临界值时，它们可能会不稳定，导致在其应用中对此类液滴的控制较少。在这项工作中，作者通过理论和实验研究，探索了圆形结构中莱顿弗罗斯特水滴的不稳定性，以及使用小棒抑制这种不稳定性。有四个发现。首先，杆容器结构内最大内接圆柱体的直径是确定莱顿弗罗斯特不稳定性的关键尺寸。其次，在水和异丙醇的情况下，该直径的阈值为 8.3 λ ± 0.3 λ，其中λ是液体的毛细管长度。第三，由于液滴与周围蒸汽层之间的特定界面轮廓，圆形容器发生不稳定的阈值直径略大于相应的瑞利-泰勒不稳定问题中的对应直径。第四，也是最后，将一根杆放置在圆形容器内可以减小容器中最大内接圆柱体的尺寸。如果该内切圆柱的直径低于阈值，则容器内部的不稳定性被抑制。