Developing unconditional moment models of turbulent combustion

Abstract

Turbulent combustion models are substantially important in CFD simulation of combustion. Some simple models frequently cannot well simulate the finite-rate chemistry. Widely recognized models are good only for certain flame types and flame structures. More general is the PDF equation model, but its computation requirement is very large, in particular when using large-eddy simulation (LES). Alternatively, the statistical moment models, such as unconditional moment models were developed based on the idea of turbulence modeling. However, the difficulty in treating the highly nonlinear exponential function of temperature in the reaction term was encountered. Different investigators adopted various approximations by neglecting different correlation terms, leading to under-predicting the time-averaged reaction rate. The present author entirely abandoned different approximations, proposed a final version of the second-order moment (SOM) model. This final version was used in both RANS modeling and LES of different single-phase and two-phase flames. It was validated by both experimental results and direct numerical simulation (DNS).

Additional information

Funding

This study was sponsored by the Project of National Natural Science Foundation of China under the Grant 51390493.