Expert’s answer : How to do open channel flow measurement
For this application, companies have used ultrasonic level transmitters for a long time. But lately, low-cost radar devices have become more popular.
Other options exist, such as floats and the bubbler method, but they’re rare. I’ve even seen a hydrostatic pressure transmitter installed on an open channel. No joke
Now let’s talk about the working principle. You measure the flow through the change of level in an open channel. So a lot of water flowing through the channel means a high level (h for head), and less water means a low level. This change is proportional to the discharge flow rate (Q):
Q = f (h)
Looks super simple, right? Of course, you need to know a few more things. To know the relationship between flow and the water level, you need to know the cross section of the open channel. Once you have that, then the curve will be the same for every level.
On the market, you can find flumes, weirs, partially filled pipes, and so on. If you know the coefficient K of each option, then you can install the device and measure the flow based on the level change. Simple as that!
This classic video will tell you more about open channel flow. Enjoy!
And these articles will tell you more about other types of flow measurement: