Effects of radiative heat transfer on the turbulence structure in reacting and inert mixing layers

We use large-eddy simulation to study the interaction between turbulence and radiative heat transfer in low-speed inert and reacting plane temporal mixing layers. An explicit filtering scheme based on approximate deconvolution is applied to treat the closure problem arising from quadratic nonlinearities of the filtered transport equations. In the reacting case, the working fluid is a mixture of ideal gases where the low-speed stream consists of hydrogen and nitrogen and the high-speed stream of oxygen and nitrogen. Both streams are premixed in a way that the free-stream densities are the same and the stoichiometric mixture fraction is 0.3. The filtered heat release term is modelled using equilibrium chemistry. In the inert case the low-speed stream consists of nitrogen at a temperature of 1000 K and the highspeed stream is pure water vapour of 2000 K, when the radiation is turned off. Simulations assuming the gas mixtures as grey gases with artificially increased Planck mean absorption coefficients are performed in which the LES code and the radiation code PRISSMA are fully coupled. In both cases radiative heat transfer is found to clearly affect fluctuations of thermodynamic variables, Reynolds stresses and budget terms like pressure-strain correlations. Source terms in the transport equation for the variance of temperature fluctuations are used to explain the decrease of this variance in the reacting case and its increase in the inert case.