Abstract: After a droplet-on-demand inkjet actuator fires a droplet, the ink chamber must be replenished before a subsequent firing. Otherwise, the resulting droplet volume can be smaller than desired, and the droplet tail can extend further, breaking into a larger number of small satellites that contribute to image quality issues and waste aerosol. The refill flow into the chambers is driven by the difference between the capillary pressure of the ink meniscus in the chamber and nozzle, and the ink supply pressure. Here, we describe modeling of the refill flow, including the hydrodynamics of refill and the capillary pressure of the ink meniscus; we also compare models with experimental data. Keywords: inkjet, hydraulics, capillarity, lumped element modelling