Sensitivity analysis of LES–CMC predictions of piloted jet flames

The sensitivity of Large Eddy Simulation with Conditional Moment Closure (LES–CMC) simulations of the Sandia piloted jet Flames D and F to various parameters have been investigated. It was found that while an LES grid may sufficiently resolve velocity fields, the conditional scalar dissipation rate obtained may still be affected by grid size due to the calculation of sub-grid scalar dissipation rate, and this can affect the degree of localised extinction predicted. A study of the relative size of the terms in the CMC equation during an extinction/reignition event showed that transport, including in the cross stream direction, plays a key role. The results are sensitive to the choice of inlet boundary conditions as extinction is only observed when the inert-mixing distributions in mixture fraction space are used as inlet conditions for the CMC equation in the primary jet and air jets.