Large Eddy Simulation and data-driven surrogate modeling of high-pressure cryogenic oxygen jets in crossflow

In this work, the mixing characteristics of a transcritical liquid oxygen jet injected into a vitiated crossflow are investigated at an operating pressure of 100 bar. A comprehensive parametric analysis is performed using Large Eddy Simulations (LES) coupled with tabulated thermochemistry to decouple the effects of the momentum flux ratio ( J ) and the jet Reynolds number ( Re j ). Results indicate that while J primarily governs global jet penetration, Re j significantly affects the near-field topology. At low Reynolds numbers, thermal expansion effects dominate over inertia, leading to a pronounced radial spreading of the dense core, whereas higher Reynolds numbers extend the liquid-like core length. To enable rapid design space exploration, the high-fidelity database is leveraged to train a resolution-invariant surrogate model based on Fourier Neural Operators (FNO). The proposed model accurately infers the time-averaged scalar field and jet trajectory for unseen operating conditions, capturing the non-linearities more effectively than classical empirical correlations. The surrogate demonstrates a speed-up of several orders of magnitude compared to the CFD solver, suggesting its potential as a tool for the preliminary design of high-pressure propulsion systems.