| Youri,
Not a stupid question in the least.
The term was coined by Vince Cichowicz, formerly the great second trumpeter with the Chicago Symphony. He found that trumpeters had a problem with connecting sounds equally from one note to the next in a slurring context and also a tongued one. He used diatonic slurred studies to increase players sense of treating all notes the same. He used the flow studies to help eliminate breaks in the embuchure, as well. The flow aspect of it refers to musical flow and physical flow.
It has come to the point where you can identify Northwestern students (Cichowizc made his fame as a teacher there) by the fact that many of them play the "Northwestern National Anthem", a Cichowicz flow study that is the first one you learn from him after you'd enter his studio.
Virtually any stepwise, slurred study can be a "flow study". The key is how you use it to better your playing.
ML |