بررسي عددي و مقدماتي تشكيل فوم تر و مطالعه ساختارهاي جريان و رفتارهاي فيزيكي مسئله

چكيده انگليسي :

Elementary and Numerical Analysis of Wet Foam Formation and Study of the Flow Structures and Physical Behavior of the Problem Sima Nasirzade vanhari s nasirzadeh@me iut ac ir July 2 2019 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree Master of Science Language FarsiSupervisor Ebrahim Shirani Prof eshirani@cc iut ac ir AbstractNowadays due to the importance of foam the availability and handling of special foam in many industries further research is needed on such a complicated flow Foam flow has become an important study issue all overthe world Most of the studies made due to its complexity focus on the geometry and topology of stationaryfoam and not on the flow itself so the importance of studying the foam flow is felt more than ever Foam iscreated by trapping pockets of gas in a liquid Some of its applications are in cosmetic raw materials topicalgels and creams lotions toothpastes shampoos and so on Foams are divided into two groups of dry foamand aqueous foam in dry foam the bubbles form polyhedral cells which are not flat and in aqueous foam thebubbles are spherical To better understand the evolution of a foam structure it is important to comprehendsome important parameters such as the void fraction the foam quality and the surface tension Surface tensionis regulated as a very essential and effective parameter in foam stability using surface active agents Surfaceactive agents play a very important role in many practical applications and when applied to a modest amountin water it significantly reduces surface tension which affects the stability of bubbles The purpose of this study is to analyze the flow of foam and to study some of the important parameters involvedin the problem such as volume fraction velocity and surface tension The most numerical researches done areflow analysis as a single phase so numerical simulation in this study is the first simulation in the foam flow inwhich both the bubbles and the water representing the fluid and gas are present in the flow and computationaldomain In this study which is a simplified mode of foam flow it is considered to be a duct in which the fluidflows through it and also bubbles get into the fluid containing a surfactant In this study a duct with dimensionsof 15 to 60 mm is considered The numerical solution was performed for three Reynolds numbers of 50 100and 1000 three volume fractions of 48 41 and 28 and three Weber numbers of 0 405 0 27 and 0 203 27 different modes and the effect of the above parameters on the flow behavior and its physical propertieshave been investigated using ANSYS FLUENT software It was found that in foam flow there is a large values of velocity fluctuations which varies with the flow param eters By increasing the Reynolds number the pressure loss increases the range of the velocity fluctuations andthe magnitude of the fluctuations decreases By increasing the Weber number the pressure loss the range of thevelocity fluctuations and the magnitude of the fluctuations decreases By increasing the foam quality pressureloss increases the range of the velocity fluctuations decreases the magnitude of the fluctuations increases andthe wall shear stress decreases And the phenomenon of coalescence causes a sudden increase in momentumspeed KeywordsAqueous foam flow Plateau border Two phase VOF method Bubble Surfactants

نصيرزاده ونهري، سيما

بررسي عددي و مقدماتي تشكيل فوم تر و مطالعه ساختارهاي جريان و رفتارهاي فيزيكي مسئله

جريان فوم تر , فيلم مايع بين حباب ها , روش دو فازي حجم سيال , حباب , مواد فعال سطحي