Proposed Benchmark Problems for Validation of Low-G SPH Slosh Models

GNC design needs to account for slosh dynamics that may interact with the GNC control system. High-fidelity CFD simulations are too slow to incorporate into GNC design simulations for all but a few limited high-value cases. There is a need for low-order slosh models, trading fidelity for speed, suitable for design work. To ground these coarser models in the high-fidelity CFD results, a set of benchmark problems is needed.

This paper presents three artificial situations designed to showcase features of particular interest to low-gravity slosh modeling: a "dam break" in a tank in a one-g field, formation of an ullage bubble in zero gravity, and fuel interaction with a propellant management device (PMD) in zero gravity. These problems lend insight into slosh dynamics excited by gravity, surface tension, and external acceleration transients. If the same problems are simulated by a high-fidelity CFD facility, the results can be used to evaluate and validate candidate low-order slosh models, and facilitate tuning of model parameters.

As a first step, the dam break problem is presented using smoothed particle hydrodynamics (SPH) as a candidate low-order model. Behavior may be qualitatively evaluated by animating the liquid-gas motion. Quantitative metrics are recorded in the form of forces on the tank, location of the fluid mass center, and kinetic, gravitational potential, and internal energy terms.