  The design and optimization of cryogenic propellant storage tanks for NASA's
future space missions require fast and accurate long-term fluid behavior
simulations. CFD codes offer high fidelity but face prohibitive computational
costs, whereas nodal codes are oversimplified and inadequate in scenarios
involving prominent three-dimensional phenomenon, such as thermal
stratification. Hence, an equation-free based data-driven coupling (EFD)
approach is developed to couple CFD and nodal codes for efficient and accurate
integrated analysis. The EFD approach, as a concurrent coupling scheme,
modifies the equation-free modeling and adapted the data-driven approaches. It
utilizes the CFD simulation results within a short co-solved period to generate
equation-free correlations through the data-driven approach. The nodal code
then solves the problem with the obtained correlations, producing "CFD-like"
solutions. This paper implements the EFD approach using the ANSYS Fluent and
the CRTech SINDA/FLUINT to investigate two-phase cryogenic tank
self-pressurization and periodic mixing problems. The EFD approach diminishes
the stratified temperature predictions errors in the top region by 89.1% and
98.9%, reducing computational time by 70% and 52%, respectively. The EFD
minimizes the risks of numerical instability and inherent correlation loss
compared to previous coupling methods, making it a flexible and easy-to-apply
approach for CFD and nodal code integrated analysis.
