Assumed PDF Modeling with Detailed Chemistry
Turbulent fluctuations exert a significant influence on chemical production rates. If finite-rate chemistry is employed the use of probability density functions (pdf) allows to account for turbulence chemistry interaction. In this paper an assumed pdf approach incorporates the effects of temperature and species fluctuations on chemical reaction rates. The pdf’s assumed are a clipped Gaussian distribution for temperture and a multivariate β-pdf for an arbitrary number of different species. Finite-rate chemistry is usually associated with large discrepancies in chemical time scales. Therefore implicit or at least point implicit numerical schemes are required for time integration. Thus the pdf-equations and pdf influenced source terms are discretized by backward Euler formulations. Results show that the high numerical stability of the employed LU-SGS algorithm is maintained. A detailed investigation of the performance of the scheme is given. This includes a comparison between NEC SX-4 and NEC SX-5.
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