As far as I know, there's no fluid dynamics simulator built into Fusion 360. But it's easy to export your geometry and do it on, e.g., SimScale.com.
There's an Autodesk product for fluid dynamics that purportedly integrates with Fusion 360, but I found the integration slipshod enough to be essentially useless. And really, it's just a very thin wrapper around exporting your geometry as a STEP file.
