Movement:
* Stream
* Current
* Surge
* Flux
* Drift
* Circulation
* Progression
* Course
Continuity:
* Sequence
* Progression
* Series
* Stream
* Continuity
Smoothness:
* Effortlessness
* Grace
* Rhythm
* Ease
* Harmony
Quantity:
* Volume
* Rate
* Output
* Throughput
Abstract:
* Process
* Dynamic
* Ebb and flow
* Rhythm
In a specific context, you could also use:
* Traffic (for cars)
* Bloodstream (for blood)
* Airflow (for air)
* Data flow (for data)
To choose the best alternative, consider the specific meaning of "flow" in your sentence and the overall tone you want to convey.