Simulating turbulence–radiation interactions using a presumed probability density function method

In turbulent combustion, the turbulent fluctuations of temperature and species concentrations have strong effects on chemical and radiative heat sources. Turbulence–chemistry interactions (TCI) and turbulence–radiation interactions (TRI) create a set of “closure” problems when the governing partial differential equations are averaged. The presumed probability distribution function (presumed-PDF) method assumes a form of probability distribution function to close the chemical source term. The emphasis of this work is developing a high-fidelity radiation model that works in tandem with combustion models that use the presumed-PDF method to close the turbulent source terms. A finite volume based photon Monte Carlo method with a line-by-line spectral model is applied with the presumed-PDFs of mixture fraction, scalar dissipation rate and enthalpy defect to account for TRI effects. An efficient wavenumber selection scheme is proposed for the line-by-line photon Monte Carlo method considering TRI. The model is validated with one-dimensional exact line-by-line solutions for different TRI treatments and with a coupled combustion simulation for an open jet flame.