School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore; Rolls-Royce@NTU Corporate Lab, N3.1-B2a-01, 50 Nanyang Avenue, Singapore 639798, Singapore.
School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore; Rolls-Royce@NTU Corporate Lab, N3.1-B2a-01, 50 Nanyang Avenue, Singapore 639798, Singapore.
Ultrason Sonochem. 2019 Nov;58:104666. doi: 10.1016/j.ultsonch.2019.104666. Epub 2019 Jul 2.
Under a vibrating ultrasonic horn device, intense cavitation occurs but is restricted to a small volume due to strong attenuation effects. In this study, milli-scale channels were introduced under the horn. The effect of this on the cavitation development and intensity within the channels were explored. High speed videography of up to 100,000 fps and acoustic signal acquisition through hydrophone were conducted. Cavitation intensity was observed to increase within the channels as compared to free field condition. Bubble density increased with a decrease in channel diameter and a rise in ultrasonic amplitude. Furthermore, an intriguing phenomenon of large bubble cluster formation near the channel exit (20 mm away from the horn surface) was detected. The oscillation behaviour of these clusters is dependent on both channel diameter and ultrasonic amplitude. At the maximum ultrasonic amplitude, the clusters reached maximum radiuses exceeding 3 mm and collapsed violently. Repetitive transient collapses near the exit region suggest that the introduction of milli-scale channels could extend the effective cavitation zone length and enhance the overall cavitation intensity under an ultrasonic horn.
在振动超声号角装置下，由于强烈的衰减效应，会发生强烈的空化现象，但空化现象会限制在一个小体积内。在本研究中，在号角下引入了毫升级别的通道。探讨了这种通道对通道内空化发展和强度的影响。通过水听器进行了高达 100,000 fps 的高速录像和声学信号采集。与自由场条件相比，观察到通道内的空化强度增加。气泡密度随着通道直径的减小和超声幅度的增加而增加。此外，还检测到了一个有趣的现象，即在通道出口（距号角表面 20 毫米处）附近形成了大的气泡簇。这些簇的振荡行为取决于通道直径和超声幅度。在最大超声幅度下，簇的最大半径超过 3 毫米，并且剧烈坍塌。在出口区域附近的反复瞬态坍塌表明，毫升级通道的引入可以延长超声号角下的有效空化区长度并提高整体空化强度。
