A Priori Analysis of an Unsteady Flamelet Formulation for Reacting Jet in Cross Flows

The jet in cross flow (JICF) configuration is a common fuel-injection strategy in practical combustion systems. Characterized by anisotropic and three-dimensional turbulent structures, enhanced mixing, and flame-dynamical processes, the modeling of reacting JICF-configurations imposes several challenges for large-eddy simulations. The objective of this study is to assess the feasibility of using an unsteady flamelet model (USFM) for the simulation of reacting JICFs. To this end, an a priori analysis of the USFM is conducted using a direct numerical simulation database, and higher-order terms in the flamelet equations, representing cross-dissipation and secondary heat-transfer processes, are quantified. It is shown that these higher-order expansion terms that are commonly neglected in one-dimensional flamelet models become of importance at the flame-base and lee-side of the JICF. Possible model-extensions are discussed to account for these secondary processes.