A numerical method is presented for computing the droplet motion in a piezoelectric inkjet process. The level-set method for tracking the liquid-gas interface is extended to treat the immersed (or irregular-shaped) solid surface of an ink nozzle. The no-slip condition at the fluid-solid interface as well as the matching conditions at the liquid-gas interface are accurately imposed by incorporating the ghost fluid approach based on a sharp-interface representation. The dynamic contact-angle condition at the immersed solid surface is implemented by employing a fast marching approach. The numerical method is applied to analyze the effects of nozzle shape, dynamic contact angle, and pressure pulse on the inkjet process.

A numerical approach is presented for computing a thermal inkjet process, in which bubble growth and collapse acts as a driving mechanism for ink droplet ejection. The liquid-vapor and liquid-air interfaces are tracked by a level-set method which is modified to include the effect of phase change at the liquid-vapor interface and is extended to treat the contact angle condition at an immersed solid surface. The compressibility effect of a bubble is also included in the analysis to account for the high vapor pressure caused by instantaneous bubble nucleation. The whole process of the thermal inkjet, including jet breaking, satellite droplet formation, and ink refill, as well as bubble growth and collapse, is simulated without employing a simplified bubble growth model.

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