The popularity of modern ink jet printers is due to a combination of high resolution printing plus low price. The printing occurs via ink droplets ejected from a tiny nozzle onto the paper. Several different methods of actuation exist, including thermal (bubble) and piezoelectric. The shape and volume of the droplet are important because they directly affect the resolution or quality of the print. The volume of fluid (VOF) model implemented in FLUENT and FIDAP allows for highly accurate modeling of free surface flows, so it is an ideal choice for the simulation of the transient ink drop ejection process. Fluent software can be used to evaluate the impact of nozzle design, actuator method and operating conditions on the droplet size distribution.

In the example below, FLUENT is used to simulate the process of drop ejection from the nozzle of a printhead in an ink jet printer. The effect of surface tension is included. The FLUENT calculation compares favorably with published results.

Comparison of the droplet shapes after 6, 12 and 18 microseconds (FLUENT results are on left, results from Reference 1 are on right).

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Reference 1: W. J. Rider, D. B. Kothe, E. G. Pucket, I. D. Aleinov, "Accurate and robust methods for variable density incompressible flows with discontinuities", Proc. Of ICASE/LaRC workshop on barriers and challenges in CFD, NASA Langley Research center, Hampton, Virginia, August 5-7, 1996, M. Salas (Ed.), Kluwer Academic Publishers.