Flow Meter Sample Code
I don't have any flow meters but my understanding is you could use the RPM Input and determine the flow rate based on the RPM. This can be used with a Conditional Function to open/close a solenoid or valve, either via on/off-open/closed or PWM to adjust the opening based on the flow range (e.g. 5 <= flow_rpm <= 10, do this, 10 <= flow_rpm <= 15, do that) . A PID could also be used with the flow RPM Input to adjust a PWM signal that adjusts a valve's opening.
Furthermore, you can create a conversion at Configure -> Measurements -> Add Conversion, for example, RPM to water speed (liters per hour), with the conversion x*10. Then in the RPM Input, you can set the conversion from measured RPM to liters per hour. This would allow for convenient measurement storage as the exact flow and makes programming downstream easier.