Extraordinarily Rapid Rise of Tiny Bubbles Sliding beneath Superhydrophobic Surfaces

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• 作者：Cyuan-Jhang Wu ; Cheng-Chung Chang ; Yu-Jane Sheng ; Heng-Kwong Tsao
• 刊名：Langmuir
• 出版年：2017
• 出版时间：February 7, 2017
• 年：2017
• 卷：33
• 期：5
• 页码：1326-1331
• 全文大小：399K
• ISSN：1520-5827

文摘

Tiny bubbles readily stick onto substrates owing to contact angle hysteresis (CAH). Nevertheless, they can slide slowly on a tilted surface with ultralow CAH because capillarity is overcome by buoyancy. It is surprising to observe experimentally that bubbles of 3–15 μL (diameter 1.79–3.06 mm) slide beneath a tilted superhydrophobic surface at a vertical ascent rate faster than that of freely rising ones of high Reynold numbers ≈O(10²). As the tilting angle increases, the drag coefficient remains essentially the same as that of a freely rising bubble, but the frontal area of the flat bubble rises monotonically. Nonetheless, the frontal area of the sliding bubble always stays much smaller than that of a freely rising bubble. Consequently, the small drag force associated with the sliding bubbles is attributed to their substantially small frontal areas on superhydrophobic surfaces.