7633

7105

كارشناسي ارشد

تبديل انرژي

اصفهان: دانشگاه صنعتي اصفهان، دانشكده مكانيك

1391

پانزده،104ص.: مصور،جدول،نمودار

ص.ع.به فارسي و انگليسي

احمدرضا پيشه ور

محمود معصومي

24/1/92

احمد سوهانكار اصفهاني، محسن دوازده امامي

مهندسي مكانيك

ID7105

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

105 Mesoscopic Simulation of Collision of a Droplet Containing Additives to a Solid Surface Using MDPD Method Marjan Zarshenas m zarshenas@me iut ac ir January 19th 2013 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M ScLanguage FarsiAhmad Reza Pishevar apishe@cc iut ac ir AbstractDrop impact phenomenon plays a remarkable role in a wide range of scientific and industrial applicationssuch as inkjet printing coating sprays decreasing water drop erosion in steam turbine blades agriculturalapplications in order to increase pesticides effect and decreasing soil erosion and even blood spatter analysisin forensic laboratories In this regard several experimental as well as theoretical and numerical studies havebeen performed Due to limitations of experimental and theoretical approaches recently numericalprocedures have been developed broadly for this purpose Among these methods multi body dissipativeparticle dynamics MDPD is an emerging particle based and meso scale scheme which is appropriate tostudy multi phase systems specially liquid vapor interfaces With respect to standard Dissipative ParticleDynamics DPD method in MDPD the conservative force consists of two parts the repulsive force whichdepends on particle local density and the attractive force which is density independent Besides like standardDPD method dissipative and random forces are used to provide viscous effects and compensate the loss ofdegrees of freedom due to coarse graining respectively According that MDPD forces are short range eachparticle interacts with those particles which is within a certain radius called cut off radius In the present work MDPD method is applied to simulate the impact of a liquid drop on a solid surface Inorder to control the behavior of drop after collision altering liquid properties by adding small amount offlexible polymers changing wettability of solid surface from hydrophobic to hydrophilic substrate areinvestigated Changing the dynamic characteristic of liquid drop as a result of initial impact velocity is alsoinquired In this regard Newtonian drop and Non Newtonian drop containing polymer with different concentration of100 300 500 and 1000 ppm are simulated using MDPD method The Non Newtonian fluid used here is alow concentration of Poly Ethylene Oxide 300k PEO dissolved in the Newtonian liquid which is 1 1mixture of distilled water and ethylene glycol Moreover solid surface has been simulated using freezed DPD particles and the particle penetration into thesolid surface is prevented by bounce back model To validate the results dimensionless spreading diameter and dimensionless drop height changes versusdimensionless time are compared with experimental results In the case of Newtonian drop impact increasing Weber enhances spreading velocity and consequentlyreduces spreading time If Weber goes up to a certain value splashing phenomenon on solid surfaces withequilibrium contact angle equal or more than 90o is observed Additionally in the case of hydrophobic orsuper hydrophobic surfaces liquid drop rebounds

احمدرضا پيشه ور

محمود معصومي

احمد سوهانكار اصفهاني، محسن دوازده امامي