北京大学工程科学讲堂 | Prof. Detlef Lohse:Bouncing Drops and Bubbles

北京日期:2021-09-13 21:13


讲座题目:

Bouncing Drops and Bubbles


讲座时间:

2021年9月17日(周五)15:30-17:00


Zoom线上会议注册:

https://zoom.com.cn/meeting/register/tJAqceupqT4tHNTkrewuSNRBQXaQxEJTH_Bp


主持人:

北京大学工学院力学与工程科学系系主任   杨越教授


开讲者:

Detlef Lohse

荷兰屯特大学杰出教授、德国科学院院士

荷兰皇家科学院院士、美国国家工程院外籍院士


 Detlef Lohse

Physics of Fluids,University of Twente, the Netherlands 

开讲学者简介

Peking University ES Seminars

Detlef Lohse studied physics at the Universities of Kiel & Bonn (Germany), and got his PhD at Univ. of Marburg (1992). He then joined Univ. of Chicago as postdoc. After his habilitation (Marburg, 1997), in 1998 he became Chair at Univ. of Twente in the Netherlands and built up the Physics of Fluids group. Since 2015 he is also Member of the Max Planck Society and of the Max-Planck Institute in Göttingen and since 2017 Honorary Professor at Tsinghua Univ., Bejing. 

 

Lohse's present research interests include turbulence and multiphase flow, micro- and nanofluidics (bubbles, drops, inkjet printing, wetting), and granular & biomedical flow. He does both fundamental and more applied science and combines experimental, theoretical, and numerical methods.

 

Lohse is Editor of J. Fluid Mech. and Ann. Rev. Fluid Mech. (among others journals) and serves as Vice-Chair for the Executive Board of the Division of Fluid Dynamics of the American Physical Society and Member of the Executive Board of IUTAM. He is Member of the (American) National Academy of Engineering (2017), of the Dutch Academy of Sciences (KNAW, 2005), the German Academy of Sciences (Leopoldina, 2002) and Fellow of APS (2002). He won various scientific prizes, among which the Spinoza Prize (NWO, 2005), the Simon Stevin Meester Prize (STW, 2009), the Physica Prize of the Dutch Physics Society (2011), the AkzoNobel Science Award (2012), two European Research Council Advanced Grants (2010 & 2017), the George K. Batchelor Prize (IUTAM, 2012), the APS Fluid Dynamics Prize (2017), the Balzan Prize (2018), and the Max Planck Medal (2019). In 2010, he got knighted to become “Ridder in de Orde van de Nederlandse Leeuw”.


讲座摘要

Peking University ES Seminars

The physicochemical hydrodynamics of droplets and bubbles out of equilibrium, in particular with phase transitions, display surprisingly rich and often counter-intuitive phenomena. In this talk Prof. Lohse will present two prototypical examples.

 

First, Prof. Lohse will show that a silicone oil drop immersed in a stably stratified ethanol-water mixture can continuously bounce up and down (with frequencies of ~1/50 Hz), if it is large enough. Smaller droplets are suspended by the Marangoni flow, which levitates the drop against gravity above its neutral density point. The transition from levitating to bouncing reveals an instability of the equilibrium between the Marangoni flow and gravity. The onset of this instability occurs when the Marangoni advection is too strong for diffusion to restore the stably stratified concentration field around the drop.

 

In the second example Prof. Lohse will discuss the nucleation and early evolution of plasmonic bubbles in a binary liquid consisting of water and ethanol. Remarkably, the plasmonic nanobubble is found to be periodically attracted to and repelled from the nanoparticle-decorated substrate, with frequencies of around a few kHz. The competition between solutal and thermal Marangoni forces is the origin of the periodic bouncing. The former arises due to the selective vaporization of ethanol at the substrate’s side of the bubble, leading to a solutal Marangoni flow towards the substrate, which pushes the bubble away. The latter arises due to the temperature gradient across the bubble, leading to a thermal Marangoni flow away from the substrate which sucks the bubble towards it.




欢迎各位同仁莅临!

Peking University ES Seminars


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