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Modeling of Turbulence–Chemistry Interaction Near the Wall

Heydari, Zahra | 2025

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 58383 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Salehi, Mahdi
  7. Abstract:
  8. Direct simulation of combustion reaction rates is highly challenging due to the complexity and computational demands involved. As a result, various statistical approaches—such as the Reynolds-Averaged Navier-Stokes (RANS) equations and Large Eddy Simulation (LES)—are commonly employed to model the interaction between flame and turbulence. Although these methods are effective, they each come with their own levels of complexity and computational cost. The introduction of a novel statistical approach, the Linear Eddy Model (LEM), has significantly improved the accuracy of combustion simulations by leveraging laminar flame structures and stochastic triple mapping techniques. The main objective of this study is to implement a suitable computational framework for applying the Linear Eddy Model within the Fluent software environment by writing custom computational fluid dynamics (CFD) code. In this framework, the focus is on unsteady simulation of both laminar and turbulent flames, while also accounting for flame–wall interactions. This simulation explicitly incorporates the effects of viscosity, molecular diffusion, reaction rates, and turbulent processes. Turbulence modeling is carried out using randomized triple mapping. The ultimate goal is to compute the probability density function (PDF) of the reaction progress variable, which serves as a critical statistical representation of combustion characteristics. This PDF is a key tool in models such as flamelet-based approaches, enabling the analysis of flame structure in complex turbulent flows, particularly near wall boundaries. Utilizing the reaction progress variable PDF not only provides a key parameter for analyzing flame–wall interaction behavior but also allows for meaningful comparison and validation of the statistical model results against those from direct numerical simulation (DNS) data
  9. Keywords:
  10. Premixed Flame ; Linear Eddy Model ; Probability Density Function ; Direct Numerical Simulation (DNS) ; Mean Vector ; Variance Analysis ; Modified Probability Density Function (PDF) ; Flame-Wall Interaction (FWI)

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