Reaction force generated if a fluid flow changes direction and/or velocity.
The force F acts on the fluid from the outside as a supporting force. The force exercised by the flow on the environment is the flow force

The force F acts on the fluid from the outside as a supporting force (reaction force).
The force exercised by the flow on the environment is the flow force
This Bernoulli force can be seen, for example, with directional valves where, during opening, it exercises an opposing force on the valve control spool for which pressure is otherwise balanced (Figure I 4).

Figure I 4: Bernoulli forces on a valve control spool