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X-WR-CALNAME:Laboratoire interdisciplinaire des énergies de demain
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BEGIN:VEVENT
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UID:MEC-6b620aedfa4cf153467265629501dd61@liedlab.net
DTSTART:20241011T060000Z
DTEND:20271010T160000Z
DTSTAMP:20250219T134400Z
CREATED:20250219
LAST-MODIFIED:20250224
PRIORITY:5
SEQUENCE:13
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SUMMARY:Study of the effect of low-frequency vibration-induced acoustic streaming on the freezing process of water droplets
DESCRIPTION:Titre :\nStudy of the effect of low-frequency vibration-induced acoustic streaming on the freezing process of water droplets\nDir. thèse : Xiaofeng Guo\nRésumé :\nHow to retard the freezing of water droplets or maintain the steady state of supercooled water is a pre-requisite basic research to solve the freezing problem of gas turbine inlet components. Compared with other additive physical fields, acoustic streaming has been proved to have a broad application prospect in the field of microfluidic control due to its unique advantages such as precise operation, low power consumption, and so on. In this thesis, the acoustic streaming method is introduced into the freezing problem of supercooled water, and the acoustic streaming is induced inside the water droplets by the method of applied low-frequency vibration to investigate its effect on the freezing process. The main contents are as follows:\n(1) The physical model of a suspended water drop under low-frequency vibration conditions is established. The first-order vibration state of the water droplet is elucidated based on the hydrodynamic theory caused by deformation. And the change rule of water drop shape is explained from the perspective of surface tension. The discussion and establishment of the physical model of a suspended water drop under low-frequency vibration conditions are carried out. Starting from the force problem of water droplets on a vibrating vertical flat plate, the physical model of suspended water droplets suitable for the description of this thesis is gradually deduced.\n(2) The generation mechanism of acoustic streaming inside a water droplet is elucidated. The reasons for the generation of the acoustic streaming field inside a water droplet are analyzed in detail, and the effect of the first-order vibration condition of the droplet on the distribution of the internal acoustic streaming field is explained. The effect of sharp edges on the acoustic streaming field is also discussed. On the basis of the theoretical derivation, the acoustic streaming field distribution inside a two-dimensional water droplet is calculated using the COMSOL finite element simulation software, and a comparison between the simulation results and the experimental results is carried out.\n(3) The mechanism of acoustic streaming in delaying the freezing of water droplets has been elucidated. The influence of acoustic streaming on the freezing process of water droplets was analyzed in detail. the variation curves of the droplet center temperature under different droplet initial temperatures, ambient temperatures and droplet sizes are given by COMSOL finite element simulation software. Transmission images of the droplet freezing process were obtained by laser irradiation, and the general internal conditions of the droplet at different freezing stages, especially the size and location of the crystals inside the droplet, were obtained.\n
URL:https://liedlab.net/events/etude-des-performances-d-interfaces-conductrices-pour-lde-developpemnt-de-revetements-routiers-degivrants-752-414-133-827-513/
ORGANIZER;CN=Yan Chen:MAILTO:
CATEGORIES:Thèses en cours
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