Sloshing mitigation in microgravity with moving baffles

We numerically investigate the effect on sloshing in microgravity of systems with passive, moving baffles whose motion is restricted by linear springs. The liquid is assumed to have physical properties similar to those of 5 cSt silicone oil while the baffle is made of aluminium. Two kinds of numerical models are developed depending on whether the allowed baffle motion is translational or rotational. Simulations show that moving baffles significantly improve sloshing mitigation compared to fixed baffles, with decreases of up to 48% in the decay time and 23% in the fluid kinetic energy following excitation by a certain pulse -like acceleration. In all configurations considered, there exists an optimal spring stiffness that minimises the kinetic energy or decay time. Frequency analysis reveals two peaks in the range of 0.1-2 Hz whose amplitudes vary as a function of spring stiffness, analogous to the behaviour of Tuned Mass Dampers (TMDs). The effectiveness of the moving baffle system is then assessed using a real microgravity perturbation measured during a reboosting manoeuvre of the International Space Station (ISS) and a significant reduction in decay time relative to the fixed baffle case is found: to 1.3 s from 4 s.