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“飞行器复杂流动与控制学科创新引智基地”学术研讨会通知多相流及自由面动力学研讨会
2018-12-06 09:30   审核人:

Workshop on multiphase flow and free surface dynamics

时 间:2018.12.07,上午09:00-12:00

地 点:西北工业大学航空楼A706

负责人:徐 翱 (Ao Xu)

会议日程

主题报告

09:00-10:00

Anatomy of splashes

By Christophe Josserand (Sorbonne University)

摘 要

Abstract

Using numerical simulations, I will discuss the formation of splashes for drop impacts on liquid surfaces. I will particularly present results on the physical properties of the jet formed at the early times of the impact. Finally, I will also discuss recent experimental and numerical results on the structure of the jet when a drop of liquid is impacting a miscible liquid of different viscosities.

个人简介

Biography

Christophe Josserand is CNRS researcher and professor at LadHyX, the fluid mechanics laboratory of the Ecole Polytechnique. He did his PhD in statistical physics at Ecole Normale Supérieure in Paris and a post-doc at the University of Chicago. Before joining LadHyX, he has been CNRS at the Institute d’Alembert, Sorbonne University in Paris. He works on surface flows and wave turbulence theory, using theoretical and numerical approaches in close collaboration with experiments.

主题报告

10:00-11:00

Freezing droplets

By Thomas Séon (Sorbonne University)

摘 要

Abstract

When a drop of water impacts a very cold substrate, the droplet freezes as it spreads and a more complex dynamics follows. We will describe this process, identifying regimes where the interface dynamics is strongly coupled with the freezing of the water. We will show in particular that the effects of the temperature can be understood within a simple one-dimensional model based on coupled heat diffusion equations. Finally, the different patterns obtained in the experiments will be described and discussed.

个人简介

Biography

Thomas Séon is a CNRS researcher at the d’Alembert Institute in Paris. He also teaches at the UniversitéPierre et Marie Curie (Paris) and at Ecole Polytechnique (Palaiseau). He studied mixing in multiphase flow for his doctorate in Paris, and after four years abroad (Universidad de Chile in Santiago, Chile, and University of British Columbia in Vancouver, Canada) he joined the d‘Alembert Institute in 2010. Since then he has been investigating various capillary hydrodynamics problems such as bubble bursting or drop impact. More recently he is interested in coupling heat transfer and phase transition to drop dynamics, this led him to work on drop evaporation and drop solidification。

Coffee Break

学术报告一

11:00-11:20

Liquid shaping based on liquid pancakes

By Xiao-Guang LI (Northwestern Polytechnical University)

摘 要

Abstract

Liquid marbles with quasi-spherical shapes have great application potential as miniature containers. Recently, their shape modification has been investigated, revealing great possibilities in broadening the uses for such containers. Current methods have demonstrated shape designability, but fine control of the final shape, important in applications, has remained a problem. Here, a facile method, based on a gravity-induced liquid pancake coated with a nanoparticle monolayer, is proposed that allows continuous segmentation of the liquid. As a result, well-shaped liquids, as structured liquid marbles with accurate target profiles, are formed. The density of interfacial particles is found to determine the segmentation feasibility and to affect the shaped liquid profile. Additionally, the maximum bifurcation is positively related to the initial particle density. This work basically achieves fine control of the liquid shape, enhancing the foundation for the development of liquid-based smart containers.

个人简介

Biography

Xiaoguang Li is an Associate Professor at Department of Applied Physics, School of Science, NPU. He received his bachelor and PhD degrees in Physics department of Tongji University in 2008 and 2013. He got joint supervision in CSIRO, Austrailia from 2010-2012. He did postdoctoral research in Tongji University and Peking University from 2013-2015 and then found his position in NPU. His current research focuses on liquid marbles and superhydrophobic surfaces.

学术报告二

11:20-11:40

A three-dimensional pseudo-potential-based lattice Boltzmann model for multiphase flows with large density ratio and variable surface tension

By Ao Xu (Northwestern Polytechnical University)

摘 要

Abstract

We present a three-dimensional pseudo-potential-based lattice Boltzmann (LB) model with an improved forcing scheme for multiphase flows. The Chapman–Enskog multiscale analysis shows that the proposed forcing scheme allows the lattice Boltzmann equation to recover the three-dimensional hydrodynamical equations with additional terms that correspond to the mechanical stability condition and surface tension. Validations of the present LB model with Maxwell construction, Laplace’s law and oscillation dynamics demonstrate that the model enables the density ratio to be as large as 700 in static and quasi-static cases while maintaining variable surface tension. Finally, the application of the model to simulation of the droplet motion in a microchannel shows that the model allows the analysis of important effects, including droplet surface tension, channel surface wettability, and channel surface roughness.

个人简介

Biography

Ao Xu is Associate ProfessorofFluid Mechanics at NPU. He received his bachelor's degree in Theoretical and Applied Mechanics from University of Science and Technology of China (USTC) in 2013, and PhD degree in Mechanical Engineering from Hong Kong University of Science and Technology (HKUST) in 2017. Dr. Xu's research is focused on numerical modeling and simulation of complex transport phenomena with emphasis on fluid flows and heat transfer. He has published 16 papers in various prestigious journals. These papers have collectively received more than 260 citations and earned Dr. Xu an h-index of 10 (Google Scholar). In the international community, Dr. Xu serves as the Managing Editor ofApplied Thermal Engineering (Elsevier).

学术报告三

11:40-12:00

Dynamic behaviour of a two-microbubble system under ultrasonic wave excitation

By Xiao Huang (Northwestern Polytechnical University)

摘 要

Abstract

Acoustic bubbles have wide and important applications in ultrasonic cleaning, sonochemistry and medical ultrasonics. A two-microbubble system (TMS) under ultrasonic wave excitation is explored by using the boundary element method (BEM) based on the potential flow theory. A parametric study of the behaviour of a TMS has been carried out in terms of the amplitude and direction of ultrasound as well as the sizes and separation distance of the two bubbles. Three regimes of the dynamic behaviour of the TMS have been identified in terms of the pressure amplitude of the ultrasonic wave.

When subject to a strong wave with the pressure amplitude of 1 atm or larger, the two microbubbles become non-spherical during the first cycle of oscillation, with two counter liquid jets formed. When subject to a weak wave with the pressure amplitude of less than 0.5 atm, two microbubbles may be attracted, repelled, or translate along the wave direction with periodic stable separation distance, depending on their size ratio. However, for the TMS under moderate waves, bubbles undergo both non-spherical oscillation and translation as well as liquid jet rebounding.

个人简介

Biography

Xiao Huang is a postdoctral researcher at the School of Marine Science and Technology of Northwestern Polytechnical University, from the year 2018. He got his Ph. D. degree from Harbin Engineering University. He is interested in the transient bubble dynamics and the characteristics of acoustic cavitation bubbles.

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