Research Project: Filtre Edilmiş Olasılık Yoğunluk Fonksiyonu Yöntemiyle Türbülanslı Yanmanın Modellenmesi
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Contributors
Funders
ID
TB.00077
Authors
Muradoğlu, Metin
Faculty Member
Publications
Large eddy simulation/probability density function modeling of turbulent swirling stratified flame series
(American Institute of Physics Inc., 2021) Muradoğlu, Metin; Türkeri, Hasret; Zhao, Xinyu; Department of Mechanical Engineering; Yes; College of Engineering
The large eddy simulation/probability density function (LES/PDF) method is applied to a turbulent swirling stratified flame series to systematically investigate its performance for accurate prediction of effects of stratification on turbulent flames under swirling conditions. The Cambridge/Sandia turbulent stratified flame series is selected as a target flame series. An augmented reduced mechanism is used for the methane/air combustion. The chemical calculations are accelerated by using the in situ adaptive tabulation method. The differential diffusion and heat loss from the bluff-body surface are taken into account in the simulations. The effect of stratification in fuel concentration is studied by increasing the stratification progressively from the pure premixed case to moderately and highly stratified cases. The performance of the LES/PDF modeling is evaluated by comparing the numerical results with the experimental data. The computed mean and rms of velocity, temperature, equivalence ratio, and mass fractions of species are found to be in good agreement with the measurements for all three conditions. Scatter plots and conditional means of mole fractions of species and temperature are presented and found to be in overall good consistency with those obtained from the experimental measurements. The recirculation zones are found to be about five times longer than those obtained under the non-swirling conditions. A low-equivalence-ratio high-temperature region near the bluff body is not captured in the computation, which is attributed to the insufficient entrainment of downstream mixtures into the recirculation zone. The parametric studies show that the differential diffusion has a minor effect on the mean and rms quantities, while the heat loss has a considerable effect on temperature and CO profiles close to the bluff body.
A new robust consistent hybrid finite-volume/particle method for solving the PDF model equations of turbulent reactive flows
(Elsevier, 2014) Muradoğlu, Metin; Sheikhsarmast, Reza Mokhtarpoor; Türkeri, Hasret; Department of Mechanical Engineering; Yes; College of Engineering
A new robust hybrid finite-volume (FV)/particle method is developed for solving joint probability density function (JPDF) model equations of statistically stationary turbulent reacting flows. The method is designed to remedy the deficiencies of the hybrid algorithm developed by Muradoglu et al. (1999, 2001). The density-based FV solver in the original hybrid algorithm has been found to be excessively dissipative and yet not very robust. To remedy these deficiencies, a pressure-based PISO algorithm in the open source FV package, OpenFOAM, is used to solve the Favre-averaged mean mass and momentum equations while a particle-based Monte Carlo algorithm is employed to solve the fluctuating velocity-turbulence frequency-compositions JPDF transport equation. The mean density is computed as a particle field and passed to the FV method. Thus the redundancy of the density fields in the original hybrid method is removed making the new hybrid algorithm more consistent at the numerical solution level. The new hybrid algorithm is first applied to simulate non-swirling cold and reacting bluff-body flows. The convergence of the method is demonstrated. In contrast with the original hybrid method, the new hybrid algorithm is very robust with respect to grid refinement and achieves grid convergence without any unphysical vortex shedding in the cold bluff-body flow case. In addition, the results are found to be in good agreement with the earlier PDF calculations and also with the available experimental data. Finally the new hybrid algorithm is successfully applied to simulate the more complicated Sydney swirling bluff-body flame 'SM1'. The method is also very robust for this difficult test case and the results are in good agreement with the available experimental data. In all the cases, the PISO-FV solver is found to be highly resilient to the noise in the mean density field extracted from the particles.
