Validation of Computational Fluid Dynamics Model of Pressure Control in a Flight-scale Liquid Hydrogen Tank using a Spray Bar

A state-of-the-art computational fluid dynamics (CFD) modeling methodology is developed to simulate depressurization tests of a flight-scale cryogenic propellant tank using a spray bar. The two-phase flow solver Loci-Stream-VOF models liquid and gaseous hydrogen as Eulerian fluid, while sub-grid scale liquid hydrogen spray droplets are represented by Lagrangian particles. The Lagrangian and Eulerian solvers are two-way coupled. Phase change for both Lagrangian droplets and Eulerian gas-liquid interface is modeled with thermal equilibrium model or gas kinetic theory based Hertz-Knudsen-Schrage model. Turbulence is captured with an improved delayed detached eddy simulation, and an asymmetric interface turbulence transport model is also employed to ensure accurate phase change and thermal gradient predictions at the Eulerian two-phase interface. Droplet breakup, coalescence and scattering are modeled based on Weber number. Without any model-parameter calibration, the methodology predicts depressurization rate with errors of -0.12% for the 50% fill-level test and -7.41% for the 90% fill-level test, achieving validation for NASA's Cryogenic Fluid Management Modeling Portfolio and demonstrating a robust Lagrangian-Eulerian model for predicting pressure control with spray bar to support NASA's human spaceflight missions.