Numerical simulation of droplet ejection of thermal inkjet printheads

Summary In this study, we present a method to predict the droplet ejection in thermal inkjet printheads including the growth and collapse of a vapor bubble and refill of the firing chamber. The three‐dimensional Navier–Stokes equations are solved using a finite‐volume approach with a fixed Cartesian mesh. The piecewise‐linear interface calculation‐based volume‐of‐fluid method is employed to track and reconstruct the ink–air interface. A geometrical computation based on Lagrangian advection is used to compute the mass flux and advance the interface. A simple and efficient model for the bubble dynamics is employed to model the effect of ink vapor on the adjacent ink liquid. To solve the surface tension‐dominated flow accurately, a hierarchical curvature‐estimation method is proposed to adapt to the local grid resolution. The numerical methods mentioned earlier have been implemented in an internal simulation code, CFD3. The numerical examples presented in the study show good performance of CFD3 in prediction of surface tension‐dominated free‐surface flows, for example, droplet ejection in thermal inkjet printing. Currently, CFD3 is used extensively for printhead development within Hewlett‐Packard. Copyright © 2015 John Wiley & Sons, Ltd. We propose a numerical method to model the droplet ejection in the thermal inkjet printheads. A bubble dynamics model is proposed to model the effect of ink vapor on the ink. A robust surface tension model and contact angle model has been developed as well. Numerical tests show good performance of the proposed method in prediction of free‐surface flows. Finally, the three‐dimensional simulation of the drop ejection process including vapor bubble growth/collapse and refill of firing chamber was carried out and compared to experiment.