There's an inkjet printer tutorial somewhere, that may be an older one on the ALH or in Fluent's Help system. That's a pretty close match to a syringe. I'd also question the need to model the piston and exiting liquid unless the back pressure on the needle alters the piston speed.
Otherwise, have a look on ansys.com as we've (Fluent and then Ansys) run a range of webinars, seminars, blogs etc over the last 20 years or so. Here's a starting point https://research.rug.nl/en/publications/computational-modelling-for-dry-powder-inhalers but consider how wide a range of applications there are too.
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