Application of the PDF transport model to nonreacting jets using an adaptive Monte Carlo method

A nonreacting methane turbulent jet flame is simulated using a composition Probability Density Function (PDF) transport model combined with a parabolic flow model closed using a k–ε turbulence model. The model is validated using the measurements of Birch et al. The turbulent concentration field of a methane jet, J. Fluid Mech., vol. 88, pp. 431–449, 1978. For the most part, the agreement between the model predictions and measured PDFs, mean mixture fraction, Root Mean Squared (RMS) mixture fraction, and higher moments is very good, except where jet intermittency effects are important. Although the validation of the model is encouraging, the requirement for large sample sizes limits how the model implemented with the standard Monte Carlo method can be taken forward. To address this issue, the Monte Carlo method is modified such that the number of particles in a control volume is adapted based on a criterion developed from the central limit theorem. The adaptive Monte Carlo method requires approximately 20% of the runtime of the standard Monte Carlo method.