Large Eddy Simulation of High-Density Ratio Hydrogen Jets

The aim of this work is the analysis of a subsonic high-density ratio hydrogen jet by using a Large Eddy Simulation (LES) model in order to gain new insights into the fluid dynamic process of turbulent mixing of compressible jets. FLEDS (Flow - Large Eddy and Direct Simulation) code has been employed, where a sixth-order compact finite difference scheme is used to discretize the governing equations. The simulation of compressible free jets is challenging in the presence of large density gradients. The injection of hydrogen in air implies high velocities, large diffusion and even higher density gradients, that can cause non-physical spurious oscillations. Therefore, a Localized Artificial Diffusivity (LAD) scheme has been implemented in order to remove the numerical instabilities, that are not dumped by the high-order non-dissipative numerical scheme employed in this work. A hydrogen jet with Mach number equal to 0.8 issuing into still air has been considered. The LES results show that the normalized centerline velocity decay rate is in good agreement with the expected theoretical steady state profile. Besides the spreading rate of the jet accounts for the effects of both the jet Mach number and the high air/hydrogen density ratio