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Modelling of Turbulence and Chemistry Interaction Using an Optimized Conditional Source-term Estimation Approach

Latifi, Mojtaba | 2022

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 54925 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Salehi, Mohammad Mahdi
  7. Abstract:
  8. The purpose of this study is to evaluate the performance of the optimized conditional source-term estimation approach. This model was first implemented in a computational fluid dynamics code, and then the Bernstein expansion was used to optimize it. For validation, two pre-mixed turbulent flames with different turbulence intensity and equivalence ratios were modeled with the optimized and RANS model. The results were obtained for mass fraction of the main and intermediate species, velocity and temperature examined in different sections. In the first flame, the turbulence intensity is low, and the flame is in the flamelet regimes; As a result, the results obtained with the optimized model are similar to the flamelet model. In this flame, the optimized model could model the assumed conditional averages in the flamelet model well. The results of velocity, temperature, main species, and hydroxide species obtained from both numerical models are consistent with each other, and the accuracy of the results is acceptable, but there is some difference in the carbon monoxide species. In the second flame, the turbulence intensity is high, and the conditional averages obtained from the optimized model are different from the assumed values in the flamelet model. Also, the flame length obtained with the optimized model is consistent with the experimental results and is more accurate than the flamelet model; And the flamelet model has overestimated the mean reaction rates and has underestimated the flame length. In examining the computational costs of the optimized conditional source-term estimation model compared to the non-optimized model, it was shown that the use of Bernstein expansion in calculating the conditional averages has greatly reduced the computational costs
  9. Keywords:
  10. Turbulent Combustion ; Conditional Moment Closure (CMC) ; Conditional Source-Term Estimation ; Reynolds Averaged ; Bernstein Decomposition ; Kinematics Interaction

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