DNS of scalar correlation-moment transport in isothermal turbulent reacting flows

The 3-D direct numerical simulation (DNS) of scalar correlation-moment transport in isothermal turbulent reacting flows was carried out by using a spectral method. The obtained statistically averaged and root-mean square (RMS) values of concentration for a single species in non-reacting flows are in good agreement with those obtained by using a finite-difference method reported in references. The instantaneous results show the existence of strip structures of concentration fluctuation for reacting flows. The DNS statistical results give the budget of the concentration correlation-moment equation, showing that the contribution of production and dissipation terms is important whereas the contribution of diffusion and reaction terms is small. However, the effect of chemical reaction on the magnitude and distribution of each term is important. The DNS statistical data are used to validate the closure models in the correlation-moment equation of Reynolds-averaged Navier-Stokes (RANS) modeling. It is found that generally the simulated values are in agreement with the DNS data in most flow regions, except in the near-wall region.