مدل سازي فرآيند تشكيل افشانه ها و قطرات ريز

چكيده انگليسي :

Modeling of spray formation and dynamics of small droplets Arash Badie Sichani a b sichani@gmail com Oct 5 2015 Department of Mechanical EngineeringIsfahan University of Technology 84156 83111 Isfahan IranSupervisor Dr M D Emami mohsen@cc iut ac irAdvisor Prof A R Pishevar apishe@cc iut ac irDepartment Graduate Program Coordinator Dr M R Salimpour Affiliation Isfahan University of TechnologyAbstractThe droplet breakup process affects spray characteristics in different ways Preliminary spray simulationsdone using OpenFOAM code indicate that the results are highly dependent to the choice of breakup model In this regard a new droplet deformation and breakup model is proposed which is capable of keeping trackof droplet distortion up to the onset of the bag rupture in bag breakup regime This is the first model toefficiently formulate dynamics of the bag with a two degree of freedom system In order to calculate modelcoefficients The Laplace equation is solved for more that 500 droplet states with different B Cs Inaddition a numerical simulation of droplet breakup using OpenFOAM with VOF method has been carriedout to validate the assumptions The results of the model are promising the critical Weber number has beenpredicted with an error of around 20 percent as compared to the experimental data Predicted distortionquantities as well as the drop profiles are validated against experiments for both vibrational and bag regime A good agreement is found between the computed results and experiments The predictions of tuned modelsfor breakup time are acceptable at near critical Weber numbers Overall achievements of the present workindicate a great potential of current approach Key WordsDrop deformation and dynamics Secondary breakup models bag breakup regime Dynamic drag modelIntroductionDroplet deformation and breakup phenomenon is considered as some important processesin spray formation Spray technology is widely used in different industries such as Spraycooling IC engines metal coating agriculture food and pharmaceutical industries Called secondary breakup this phenomenon has an important role in such applications fordetermining the penetration length of liquid phase droplet size distribution andevaporation rate Exhibited in Figure 1 the numerical simulations of a high pressurespray using the OpenFOAM code indicate that the results are highly dependent to thechoice of breakup model Therefore it is justifiable to investigate the ways for bettermodeling of droplet breakup Numerical analysis of secondary atomization is a challenging problem because simulationof a domain containing millions of droplets using traditional methods for multiphaseflows such as Volume of Fluid VoF is computationally very expensive or evenimpractical Nowadays using the Lagrangian description for simulating thin sprays hasbecome common regarding their reasonable computational cost Several methods havebeen proposed for modeling the breakup process in a Lagrangian scheme One of themost famous models suitable for low Weber numbers is the TAB model 1 In thismodel inspired by the similarity between oscillations of a drop with a mass spring damper system a second order linear differential equation is proposed to calculate theevolution of the droplet shape from spherical to ellipsoidal Other models which areclassified under this category are DDB 2 NL TAB 3 T TAB 4 Other than

بديع سيچاني، آرش

مدل سازي فرآيند تشكيل افشانه ها و قطرات ريز

مدل شكست ثانويه , ديناميك قطره , معادلات لاگرنژ , مدل ضريب درگ ديناميكي