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چكيده انگليسي :

Turbulence Modeling in Interfacial Flows with Large Eddy Simulation Technique Mahmood Charmiyan m charmiyan@me iut ac ir Date of Submission 2011 05 9 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Ebrahim Shirani eshirani@cc iut ac irAbstractMany industrial and environmental applications involve high Reynolds number turbulent multiphase flows Examples include spray formations fuel injectors oil transportation sea aerosol formation and many others Agreat deal of research effort has been oriented towards the numerical modeling of multiphase turbulent flows The great majority of numerical computations have adopted Reynolds Averaged Navier Stokes RANS modeling in which shear and multiphase induced turbulence is considered Large Eddy Simulation LES hasbeen also utilized for multiphase flow calculations of particles smaller than the Kolmogorov scale undeformable interfaces bubble formation and break up turbulent plane jet and liquid film interaction or wavebreaking In this study the turbulence interfacial flows are studied by means of LES Since turbulence near theinterface is highly anisotropic due to the presence of surface tension force and also the advection at the interfacehighly depends on the topology of the interface the simulation of the interface is very crucial and special care istaken in this work to carefully model the turbulence at the interface In the interfacial flows when LES is used the new sub grid scales terms related to turbulence of surface tension and advection terms are modeled In this research two new dynamic models are developed to simulate terms related to sub grid scales of surfacetension and advection equations This new dynamic models are developed for sub grid surface tension in orderto account this terms that vanished by LES filtering In this study in order to track the interface VOF PLIC is deployed and in order to calculate the surface tensionforces Continuous Surface Force CSF model is used Also centered differencing is used for momentumadvection and stability is preserved with the help of the dissipation contribution from explicit SGS modeling The standard Smagorinsky kernel based SGS model was employed using a value of the damping constant Cs 0 1 and The SIMPLEC scheme is used for the pressure velocity To validate the presented model the inversion phase of water and oil problem is studied The flow induced bythe action of the buoyancy force due to oil inclusion in a cavity full of viscous water is studied Since the densitydifference effect is counteracted by the viscous and surface tension forces an unsteady turbulent two phase flowdevelops This leads to strong interface shearing and stretching accompanied with drop extraction andcollapsing In this regard this case study is aimed at testing the ability of the numerical method to simulateturbulent two phase flows with large and dynamic interface deformations Due to the complexity of the flow the detailed structure cannot be analyzed and compared to any reference solution Moreover the detailed timeevolution of the transient phase may be not completely resolved at each time step due to the fine structure of theeddies that are produced Therefore this case study is potentially appropriate to investigate the ability ofnumerical simulation method of two phase flows associated with large dynamic deformations The resultsobtained for the inversion phase of water and oil problems are in good agreements with that of Direct NumericalSimulation DNS technique and as a result the presented dynamic model is capable of simulating theinterfacial flows LES results have demonstrated that specific sub grid surface tension and advection eqautionintroduced by the LES formulation of turbulent two phase flows cannot be neglected particularly due to thepresence of an interface In the end there is a summary of thesis and suggestions for further studies Keywords two phase turbulent flow turb

چرميان، محمود

شبيه سازي جريان هاي آشفته همراه با سطح مشترك توسط روش شبيه سازي ادي هاي بزرگ

مدل كردن تلاطم كشش سطحي , روش VOF-PLIC , csf