شبيه سازي جريان هاي احتراقي با استفاده از مدل جبري مغشوش شار اسكالر و تنش رينولدز

چكيده انگليسي :

Numerical Simulation of Reacting Flows Using Algebraic Scalar Flux and Reynolds Stress Models Ali Hajighasemi a hajighasemi@me iut ac ir Date of Submission 2015 08 10 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Mohsen Davazdah Emami Mohsen@cc iut ac irAbstract Turbulence modeling is among the most important challenges for the researchers Over the past decades different models have been proposed to explain the behavior of turbulent flows An important feature ofturbulent flows is the chaotic characteristics of the flow field Such a feature has led researchers to adoptstatistical approaches in tackling turbulence modeling challenge The averaging method in which theinstantaneous quantities are decomposed into the mean and fluctuating components is a well knownapproach in turbulence modeling As a result of this scheme new unknowns are introduced into the governingequations that are subject to further modeling Accuracy in predicting turbulent flow quantities will lead toprecise prediction of the flow field and thus accuracy in all of the numerical simulation results Modeling andsimulation of turbulent reacting flows have been the focus of many researches In order to simulate turbulentreacting flows an appropriate combustion model is required Due to separating chemical reactionscalculations from the solution of turbulent flow field the present flamelet model provides the possibility ofconsidering chemical kinetic with any level of complexity The purpose of this study is to evaluate theperformance of various models of turbulent flux and Reynolds stress in turbulent reacting flows The modelconsidered in this study are the Reynolds stress model RSM Algebraic Reynolds Stress ARSM andturbulent flux models In order to validate and choose the best model for turbulent flux channel Couette andbackward facing step flows are studied in this study Considered turbulent flux models include the standardmodel Boussinesq analogy the Daly and Harlow model and the Abe and Suga model Simulation resultsshow that the standard gradient model gives good predictions for normal heat flux but fails to predict thestream wise heat flux errors up to 100 It is also verified that the model of Abe and Suga accuratelypredicts the normal heat flux and by a 25 enhancement yields good predictions for the stream wise heatflux The model of Daly and Harlow also accurately predicts the normal heat flux profiles but underestimatesthe stream wise heat flux despite showing its correct trend The Abe and Suga model predicts best results andis more consistent with the experimental data than the other two models Subsequently the reactive flow arestudied for the case of a non premixed bluff body flames using turbulent flux of Abe and Suga AlgebraicReynolds Stress ASM and Reynolds Stress RSM models Results of various turbulent flow models forvelocity field temperature field species mass fraction and mixture fraction are compared with each other The result reveals a good agreement with the experimental data In this study the results of reacting flowfield in a swirl burner is also provided and axial velocity swirl velocity temperature distribution and oxygenconcentration are presented at different cross sections Results show that the combined model of Reynoldsstress and Abe and Suga improves the prediction of turbulent flows Keywords Turbulent Flow Turbulent Flux Model Flamelet model Algebraic Reynolds StressModel Non Premixed Flame

حاجي قاسمي، علي

شبيه سازي جريان هاي احتراقي با استفاده از مدل جبري مغشوش شار اسكالر و تنش رينولدز

مدل تنش جبري , شعله غير پيش مخلوط