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Turbulence Equation-of-State Interaction Modeling in Large Eddy Simulation

Ghayour, Amir Mohammad | 2022

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 55810 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Salehi, Mohammad Mahdi
  7. Abstract:
  8. In most real combustion systems, flow is turbulent (e.g., diesel engines). Therefore, a reliable turbulence modeling approach is necessary to design and analyze a system with turbulent flow. Direct numerical simulation (DNS), Large eddy simulation (LES), and Reynolds-averaged Navier-Stokes (RANS) are the three most mature Computational fluid dynamics (CFD) methods for turbulent flow simulations. Because of LES’s good accuracy and acceptable computational cost. In this project, LES is chosen to simulate the turbulent flow field.Modeled turbulence subgrid scales' interaction with nonlinear flow parameters, needs modeling. In supercritical and transcritical conditions, Equation-of-state is a non-linear function. In pressure-based CFD solvers, the EoS is used to calculate the density. Therefore, turbulent flow simulations with high-density gradient may need a closure equation to model the unresolved turbulence scales interaction with EoS. In this project, a closure equation is developed based on the presumed probability density function, to model the turbulence-EoS interaction in LES simulation. Then, the closure equation is used to obtain the regime diagram to evaluate the necessity of implementing and using this closure model in scientific applications. A LES simulation of a case in supercritical condition was performed in this project. In this simulation, first of all, turbulent flow in a pipe is simulated, and the flow field is imported into the main geometry as the turbulent flow boundary condition. Finally, the results of LES have been verified by experimental data
  9. Keywords:
  10. Large Eddy Simulation (LES) ; Computational Fluid Dynamics (CFD) ; Supercritical Fluid ; Probability Density Function ; Direct Numerical Simulation (DNS) ; Reynolds Average Navier-Stocks (RANS)Method ; Turbulence-State Equation Interaction ; Presumed Probability Density Function

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